A Novel Method for Damage Prediction in BCF/PEEK Drilling Using an Innovative Drill Tool

A Novel Method for Damage Prediction in BCF/PEEK Drilling Using an Innovative Drill Tool | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article A Novel Method for Damage Prediction in BCF/PEEK Drilling Using an Innovative Drill Tool Yong Liu, Shenao Zhu, Guangyao Xu, Meng Zhu, Zitao Pan This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4480703/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 05 Mar, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted 5 You are reading this latest preprint version Abstract The effective design of tool geometry and optimization of process parameters play a pivotal role in mitigating damages such as tearing, burrs, and delamination during the drilling process of braided carbon fiber reinforced poly ether ether ketone (BCF/PEEK). This study introduces a novel method for selecting optimal drilling tools and damage prediction analysis in BCF/PEEK drilling. Firstly, a scale-span drilling finite element (FE) model is established based on the analysis of twist bit geometry and BCF/PEEK composition. Simulation and experimental validation identify damage causes in prefabricated holes. Subsequently, three innovative types of designed drilling tools are evaluated based on factors like hole morphology, thrust force, and delamination. Finally, Regression models are established to correlate damage factors, thrust force, and process parameters. The research findings indicate that the use of twist drill bits results in higher thrust forces, leading to delamination defects at hole exits. Conversely, employing a tapered drill-reamer could enhance the exit quality of prefabricated holes, consistently maintaining damage factors below 1.14 under identical process parameters. The proposed method effectively predicts the exceptional process parameters, with a maximum error of only 0.276% in the drilling of BCF/PEEK. BCF/PEEK Scale-span drilling FE model Drilling tools Process parameters prediction Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 1. Introduction Carbon fiber reinforced thermoplastic plastics (CFRTP) constitutes a novel class of composites manufactured through intricate processes such as impregnation and molding, utilizing high-temperature-resistant resin as the matrix and high-performance carbon fiber filaments as the reinforcement [ 1 ]. In comparison to carbon fiber-reinforced plastic (CFRP), CFRTP offers notable advantages, including enhanced corrosion resistance, lightweight, rapid and cost-effective manufacturing, as well as recyclability [ 2 ] [ 3 ]. Poly ether ether ketone (PEEK) is an outstandingly versatile specialty engineering plastic, characterized by exceptional heat resistance, resistance to hydrolysis, excellent chemical resistance, electrical insulation properties, and radiation resistance, especially when braided carbon fiber and PEEK resin are combined to form braided carbon fiber reinforced poly ether ether ketone (BCF/PEEK). These attributes ensure dimensional stability in extreme environments, which has garnered extensive attention in the civil aviation sector [ 4 ]. For instance, PEEK is utilized by Boeing Corporation in the injection molding process to manufacture engine nacelles for the B757. This composite demonstrates resilience under harsh conditions, resulting in a weight reduction of approximately 30% compared to aluminum alloy or titanium alloy products, accompanied by a cost reduction of around 90% [ 5 ]. Additionally, PEEK has been employed by Stelia Corporation to manufacture a full-scale thermoplastic fuselage demonstrator, aimed at assessing the feasibility of using thermoplastic composites in the next generation of single-aisle aircraft [ 6 ]. The predominant method for composite structure assembly in the aerospace manufacturing industry is composed by mechanical connections, represented by rivets and bolts [ 7 ]. Substantial drilling and hole-making operations are involved in the riveting and bolting processes, and the tensile strength and fatigue damage of structural components are significantly influenced by high-quality hole-making[ 8 ]. The drilling of CFRTP using conventional cutting tools is susceptible to processing damage such as tearing, burrs, and delamination at hole exits [ 9 ]-[ 11 ], thereby compromising the reliability of the product. The traditional twist drill exhibits a relatively long transverse cutting edge, and during the drilling process of composites, approximately 60% of the total thrust force is generated by the transverse edge, thereby leading to the occurrence of delamination at hole exits [ 12 ]. A drilling experiment on carbon fiber composite was conducted by Qiu et al [ 13 ], and the results showed that traditional twist drilling could not achieve high-quality drilling, while step drilling could improve the quality of hole making. The quality of drilling can also be directly affected by the selection of process parameters [ 14 ]. The influence of drilling process parameters on the delamination damage of carbon fiber composite was analyzed by Gaitonde et al. [ 15 ] through experimental research, and they found that stripping delamination of holes can be reduced when high-speed machining is carried out. Therefore, reasonable drilling tool selection and process parameter optimization are the main methods to achieve high-quality hole making of thermoplastic composites. Currently, research on hole-making in composites primarily focuses on two aspects. one involves the investigation of drilling tools, and the other entails the optimization and prediction of drilling process parameters. Extensive research has been conducted on the characteristics of drilling composites using various structural tools, with significant manifestations evident in both research methodologies and outcomes. For instance, drilling experiments with different spindle rotation speeds and feed rates were conducted by Wang et al. [ 16 ] comparing the influence of different drilling methods on hole quality. The results showed that drilling with a ladder bit produced less thrust, less delamination damage, and the highest hole-making quality. A new auger cutting tool was proposed by Kong et al. [ 17 ] to replace the traditional auger end milling cutter, realizing auger drilling and reaming processing, and effectively inhibiting the drilling damage of composite laminates. PCD twist drills and special diamond-coated double-tip drills were used by Al-wandi et al. [ 18 ] to carry out drilling experiments on composites, and the results were verified through FE analysis, concluding that double-tip drilling resulted in higher hole quality. Using the Box-Behnken design method, Palanikumar et al. [ 19 ] conducted experiments to establish the empirical relationship of GFRTP thrust force and analyzed the factors and functions affecting drilling in detail. Through experiments, Mudhukrishnan et al. [ 20 ] concluded that borehole quality was better when the spindle rotation speed was 2500r/min and the feed speed was 0.05mm/r. Regression models of borehole surface roughness and aperture error were established respectively using the experimental data, with a very strong correlation observed. Feito et al. [ 21 ] utilized a simplified model to study the effects of thrust force, laminate bottom clamping area, and laminate sequence on delamination damage during the drilling of carbon fiber-reinforced composite. The calculation cost was low, but the predicted value of the delamination factor was slightly higher. A mathematical model of the relationship between processing parameters and delamination damage was established by Mudhukrishnan et al. [ 22 ], obtaining an empirical relationship that can better predict delamination damage during composite drilling. Regarding scholars studying CFRP drilling, plentiful studies have extensively focused on the laminated structures of thermoset composites. While some research on woven structures exists, the damage mechanisms and mechanical behavior during the processing of CFRTP significantly differ from those of CFRP [ 23 ], thereby imposing certain limitations on the research. Meanwhile, research on CFRTP is also influenced by its manufacturing processes, with the current emphasis predominantly placed on laminated structures. The existing research on drilling CFRTP has not systematically analyzed the shortcomings of traditional drilling tool structures. Moreover, the research in this area is relatively singular, and when it comes to drilling experiments using novel drilling tools, there is a lack of cross-tool comparison in terms of drilling quality, rendering the obtained data relatively incomplete. Additionally, there is relatively limited research on the subsequent processing and in-depth analysis of drilling data. Determining pre-drilled hole’s quality under real process parameters still necessitates specific drilling experiments, entailing significant investments in terms of manpower and time costs. Most existing predictive models primarily conduct analytical predictions under individual process parameters (such as spindle rotation speed or feed rate) and lack effective experimental validation. Addressing certain issues identified in the preceding studies, this study proposes a method to optimize drilling tools and damage prediction analysis in BCF/PEEK drilling. Initially, a scale-span drilling FE model of BCF/PEEK employing a twist bit is developed based on modified micromechanics of failure criterion with new damage evolution laws. The causes of damage defects in prefabricated holes induced by twist drills are analyzed, and the accuracy of the simulation model is validated through experiments. Subsequently, three types of innovative tools are devised, and orthogonal experiments on drilling BCF/PEEK are conducted. Exit orifice morphology, thrust force, and damage factors are meticulously observed and recorded, facilitating a comparative analysis of the drilling performance of each tool. Then, by utilizing thrust force as the intermediate variable, regression models are established separately for the relationships between damage factors and thrust force, as well as between thrust force and process parameters. Regression equations for each relationship are derived through fitting. Furthermore, the correlation between the damage factor and process parameters is determined, and a hierarchical damage prediction method oriented towards process parameters is proposed. Two groups of extreme and exceptional process parameters are validated through the corresponding experiments. 2. Damage mechanism analysis on drilling BCF/PEEK using twist drill 2.1 Scale-span FE analysis of twist drill drilling A drilling scale-span FE model for BCF/PEEK using a twist drill was developed on the ABAQUS/Explicit software platform in this study. The twist drill bit model was created in SolidWorks software based on the geometric parameters of the drill's solid structure and then imported into ABAQUS for implementation. Following our prior research [ 24 ] [ 25 ], the three-dimensional model structure of BCF/PEEK was defined using the VUMAT subroutine to incorporate internal damage formulation via the proposed dynamic three-dimensional scale-span model, which is based on a modified micromechanics of failure criterion with new damage evolution laws. Material removal simulation during cutting action was accomplished using methods such as element stiffness degradation and removal. Additionally, a failure analysis model of cohesive elements (CEs) based on a mixed-mode failure criterion [ 26 ] was established within the braided structure of BCF/PEEK to simulate delamination phenomena that occur during the drilling process. Furthermore, the length of the cohesive elements zone was selected to be approximately 2–3 times the length of an element side, chosen to regularize the delamination fracture toughness and mitigate mesh sensitivity. According to the above description, the comprehensive scale-span simulation model for drilling BCF/PEEK is illustrated in Fig. 1 , which is encompassing the configuration of boundary conditions and the structural parameter of the twist bit. The focus of this study is mainly investigating the scale-span analysis of BCF/PEEK in the entire drilling process, with the research subject being a CFRTP composed of 6K Toray T800S carbon fibers and a high-temperature resistant resin, denoted as BCF/PEEK. The density of prepreg is 200g/m 2 . Utilizing a braided structure, the overall dimensions of the BCF/PEEK laminate were 14.70mm×14.70mm×4.05mm, comprising a total of 32 layers. To achieve a comprehensive and accurate prediction of thrust force and torque during the drilling process, the twist drill with a 6mm diameter (coated with AlTiN) was modeled as a discrete rigid body. The total mass and rotational inertia of the twist drill were constrained at the top reference point. Boundary conditions were applied based on this reference point, including the feed rate and rotation speed of the drill bit. To enhance computational efficiency and conserve computational resources, mesh refinement was applied to the drilling contact region of the BCF/PEEK laminated plate (a circular area with a diameter of 10mm). Meanwhile, coarser meshes were employed in the vicinity of the laminate edges and the twist drill to optimize the simulation. The BCF/PEEK is modeled using C3D8RT elements, which are 8-node, three-dimensional reduced integration elements. The twist drill was represented using C3D8RT discrete rigid body elements. In accordance with the actual machining conditions, where the drill was fed along the Z direction into the BCF/PEEK, boundary conditions such as rotation speed and feed rate were applied to the entire drilling FE model. Since the motion state of the twist drill model was constrained at the top reference point, displacements in the X and Y directions at the reference point were restricted, while a feed velocity was applied in the Z direction. Similarly, rotational speeds in the X and Y directions were constrained, a clockwise rotational velocity was imposed in the Z direction, and the four vertical surfaces of BCF/PEEK were fixed. To simulate the occurrence of burrs during the drilling process, the mesh size of the BCF/PEEK elements needed to be on the scale of the fiber bundles. Based on the optimization analysis of the sensitivity model for element mesh, the entire scale-span drilling FE model comprised a total of 235,420 elements. This included 235,200 hexahedral elements for the BCF/PEEK and 220 tetrahedral elements for the twist drill. The minimum size of the BCF/PEEK elements was approximately 208×208×83µm. In the predefined global coordinate system, a transversely isotropic material, namely UD-PEEK, was assigned to the single fiber bundle of BCF/PEEK along the fiber direction. Among them, the unidirectional paving structure parameters of BCF/PEEK are shown in Table 1 , and the attribute parameters of CEs are shown in Table 2 . Table 1 The unidirectional prepreg material property parameters of BCF/PEEK Performance index Value Performance index Value The areal-density of prepreg fiber (g/m 3 ) 160 Elongation of carbon fiber 2% The areal-density of the prepreg (g/m 3 ) 242 The density of carbon fiber (g/m 3 ) 1.8 The density of BCF/PEEK (g/m 3 ) 1.57 The density of PEEK (g/m 3 ) 1.35 Tensile strength of carbon fiber (MPa) 4900 Bending strength of PEEK (MPa) 150 Tensile modulus of carbon fiber (GPa) 230 Bending modulus of PEEK (GPa) 4 Table 2 The material property parameters of CEs Stiffness parameter Value (N/mm 3 ) Stiffness parameter Value (MPa) Fracture energy parameter Value (N/mm) K n 4×10 6 δ n 60 G n 0.2 K s =K t 1×10 6 δ s = δ t 90 G s =G t 1 The entire scale-span FE model had been subjected to a complete factorial design employing three levels for the machining parameters [ 14 ]. Specifically, the twist drill spindle rotation speeds ( Sr ) of 2000 rpm, 3000 rpm, and 4000 rpm, as well as the feed rates ( Sf ) of 0.01 mm/rev, 0.02 mm/rev, and 0.03 mm/rev, were respectively applied within the model. In order to analyze the damage incurred by twist drills with different parameters on BCF/PEEK models with varying ply orientations, a scale-span FE model was developed. The contact behavior between the drill bit and BCF/PEEK was simulated using a penalty-based Coulomb friction model. A friction coefficient of 0.3 was applied in the normal direction of the contact. The face-to-face contact between the twist drill and the BCF/PEEK model was implemented using explicit dynamics, wherein the twist drill surface nodes interacted with the BCF/PEEK element nodes. The twist drill surface was designated as the master surface in the contact configuration. To save computational time, only the central circular region with a diameter of 10mm and its interior within the BCF/PEEK material were defined as facets (formed based on element nodes). Based on the aforementioned settings, jobs were created and the corresponding calculation input file was output to check for errors. The mass scaling factor was set to 10 3 according to the reference [ 27 ] to improve computational efficiency on the premise of ensuring accuracy through many attempts. The complete computation of a job required approximately 163 hours on a high-performance computer with two 48 core 8180M platinum processors and 128 GB RAM. All simulations were performed at the high-performance computing facility at Jiangsu University of Science and Technology. 2.2 Damage mechanism analysis and experimental verification After preparation and mechanical properties testing, the BCF/PEEK workpieces were transformed into drilling specimens by cutting according to the design of a special fixture, and at least two drilling test specimens of each type were required to ensure the accuracy of test results. Meanwhile, a suitable experimental platform based on the vertical machining center for drilling experiments was established. The whole experimental platform consists of the thrust force data acquisition module and temperature data acquisition module. The experiment was conducted on the CNC machinery DX-650 vertical machining center. The spindle rotation speed of the machine tool could reach up to 30000r/min, the main motor power was 5.5kW, and the positioning accuracy was 0.005mm, and the schematic diagram of the experimental platform and the connection relationship of each part is shown in Fig. 2 . Meanwhile, the heat generated during drilling of composite is prone to causing thermal damage to the composite. Therefore, the FPR-A615 infrared thermal imager was utilized, which had a thermal sensitivity of < 0.05 \(℃\) and an accuracy of ± 2 \(℃\) , and the measuring range could reach − 40 \(℃\) to 2000 \(℃\) , effectively fulfilling the function of temperature monitoring. In addition, the data of thrust force and torque were collected by the Kistler-9129AA dynamometer. The sampling frequency was 5000Hz, and the sampling time was set to 45 s . The Kistler-9129AA was installed on the machining platform of the machining center through a special fixture. The fixture was mounted on the upper part of the dynamometer via a bolt, and the acoustic emission sensor was affixed to one side of the fixture through a magnetic pressure head. According to the analysis results of the scale-span FE model and experimental results which are shown in Fig. 4 (a), the entire drilling process can be divided into four phases according to the interaction effects between twist drill bit and BCF/PEEK. In phase 1: the tool tip progressively penetrates the material, increasing the contact area between the tool face and the workpiece. Simultaneously, both thrust force and temperature steadily escalate. In phase 2: With the tool tip fully immersed in the material, the primary cutting edge actively cuts within the workpiece. Consequently, the material's stiffness starts to diminish, causing the rate of thrust force increase to slow down. Despite this deceleration, both thrust force and temperature continue to rise gradually, peaking in this phase. In phase 3: the tool tip has penetrated through the material, and the primary cutting edge is reaming within the workpiece. As the material's stiffness decreases further, thrust force experiences a rapid decline, while temperature gradually decreases. In phase 4: the primary cutting edge emerges from the workpiece surface. The decline in thrust force stabilizes, while temperature continues to decrease. With the tool completely withdrawn from the workpiece, the drilling process concludes once the tool bit is lifted. Under such a large thrust force, the phenomenon of debonding and delamination between laminates was prone to occur. From the cross-section of BCF/PEEK, it could be seen that under a large thrust force, there was obvious delamination damage between each layer, and the quality of hole making was particularly poor, as shown in Fig. 3 and Fig. 4 (b). The various process parameters of the drilling experiment were also selected in accordance with the settings of the above scale-span FE analysis, namely, the spindle rotation speed was set to n = 5000r/min, and the feed speed was set to f = 120mm/min. Following all drilling experiments, the morphology of the hole outlet and hole wall was observed using the INSIZE ISM-PM600SB digital microscope and DSX series microscope, respectively. Prior to observing the morphology of the hole wall, the hole was cut using a cutting machine, and half of the hole wall with better integrity was selected for observation, which is illustrated in Fig. 3 . These corresponding experimental results observed that the hole-making quality of the traditional twist drill was poor, with large areas of tearing and patches of burr, serious delamination, low cylindricity of the hole, poor edge uniformity at the exit, and large hole wall roughness. Based on the above research and analysis, the defects of twist drills in the drilling of BCF/PEEK were as follows: the thrust force in the drilling process was too large due to the thrust effect of the transverse edge, and the extrusion effect of the cutting edge on the material exceeded its shear effect, resulting in obvious delamination between the laminates. The process parameters suitable for the drilling of BCF/PEEK were selected through a combined analysis method involving scale-span FE simulation and experimentation. However, it was observed that the drilling quality of traditional twist drills was poor in all results. Therefore, for achieving high-quality drilling of BCF/PEEK, it is necessary not only to select the appropriate process parameters but also to design a tool with a new bit structure and analyze its drilling characteristics. 3. Experiment of drilling holes with different novel tool 3.1 Drilling tool design and experimental scheme In response to the issue of poor hole quality in composite drilling caused by conventional twist drills, it is deemed necessary to design new tools for composite drilling. Due to the significantly lower bonding strength of the composite matrix resin compared to the tensile strength of the fibers, the interlaminar shear and tensile strength of the composite are considerably low. The transverse cutting action of the conventional twist drill is minimal, primarily involving the rolling and crushing of fibers, which, however, constitutes the primary source of thrust force [ 28 ]. Therefore, considering the research presented in the previous chapter and the findings of previous studies, the longer transverse cutting structure of the traditional twist drill should be abandoned in the design of the new tools. This is done to enhance the shear capability of the fibers and reduce the generation of thrust drilling force, thereby improving hole quality. Following this principle, three novel drilling tools were designed: the dagger drill, the three-point twist drill and the three-point drilling and milling cutter, as shown in Fig. 5 (a), (b) and (c). To investigate the performance of various new tools in drilling BCF/PEEK, drilling experiments were conducted on BCF/PEEK specimen plates. The diameters of the three new cutting tools were all 6mm. Among them, two three-point drills were designed by significantly reducing the transverse cutting length compared to the traditional twist drill, until it was transformed into a single cutting edge. This design allowed for a substantial reduction in the generation of thrust force. In addition to the primary cutting edge playing a role in cutting, an auxiliary cutting edge was also involved in the cutting process of the three-point twist drill, thereby enhancing its shear capability on fibers and reducing the occurrence of machining defects. The structure is illustrated in Fig. 6 (a). The head of the three-point drilling and milling cutter featured a W-shaped structure with three points, and the sharp cutting tips on both sides could easily sever the fiber bundles of the composite, as depicted in Fig. 6 (b). The dagger drill, in contrast, was devoid of chip flutes, aiming to further minimize thrust forces. The corresponding drill head was essentially a combined drilling and reaming tool, with the point portion divided into the first cutting edge and the second cutting edge. During the drilling process, four peripheral cutting edges were directly involved in cutting, showcasing strong cutting capabilities. Hence, high-quality holes could be drilled. The main parameters of the dagger drill structure are presented in Table 3 . Table 3 The main structural parameters of the dagger drilling structure D 1 (mm) h 1 (mm) α d 1 (mm) h 2 (mm) β 2 2 118° 6 6 50° In order to investigate the pre-drilled hole’s quality indicators such as forces and exit quality under various drilling parameters for different tool structures, an orthogonal experimental approach was employed in this study. For each type of tool, a double-factor, four-level orthogonal experiment was designed, with factor levels as presented in Table 4 . Table 4 Orthogonal experimental scheme Number n /(r/min) f /(mm/min) Number n /(r/min) f /(mm/min) 1 2000 30 9 2000 50 2 3000 30 10 3000 50 3 4000 30 11 4000 50 4 5000 30 12 5000 50 5 2000 40 13 2000 60 6 3000 40 14 3000 60 7 4000 40 15 4000 60 8 5000 40 16 5000 60 The borehole arrangement of the specimen plate was as follows: approximately 10mm of space was left on both sides of the specimen plate in the longitudinal direction for clamping by the fixture. Subsequently, perforated holes were drilled on the specimen plate with different process parameters using a numerical control machining program. The center positions of every two holes were spaced 15mm apart. Each plate could accommodate 4×5 = 20 holes, with one row designated as a reserve drilling area for holes where the drilling effect was suboptimal or data had not been collected, as illustrated in Fig. 7 . During each drilling operation, the thrust force was monitored in real time, and images of the hole exit morphology were captured using a microscope. This was done to facilitate a comparative analysis of the drilling characteristics of different novel cutting tools in BCF/PEEK. 3.2 Analysis and discussion of experimental results (1) Macro evaluation of drilling damage For the holes obtained through drilling operations, the exit quality of the bore was observed using the INSIZE ISM-PM600SB digital microscope, and photographs of the exit morphology were taken for documentation. Varying degrees of damage were observed in the holes drilled by the three different types of tools, as inferred from the exit morphology of the holes. The exit morphology of the holes drilled by the three types of tools is depicted in Fig. 8 . Taking as an example the holes produced by drilling with process parameters of spindle rotation speed at 2000 r/min and feed rate at 30 mm/min, a comparative analysis of the bore quality for each tool was conducted. The exit morphology of the holes drilled by the dagger drill is illustrated in Fig. 8 (a). Fine fibrous burrs distributed at the exit of the hole could be observed. The overall neatness of the hole exit contour was relatively high, and its cylindricity was the highest among the holes drilled by the three types of tools. Comparatively, the best quality of pre-drilled hole is showed in Fig. 8 (b). Additionally, there were no apparent layering phenomena, indicating the optimal quality of bore production. The exit morphology of the holes processed by the three-point twist drill is depicted in Fig. 8 (b). In the extremely small edge region of the hole, there was minimal occurrence of short fibrous burrs, with the fibrous burrs being the least distributed among the three types of drill bits. The cylindricity of the hole was relatively high; however, there were evident manifestations of tearing and layering. The holes drilled by the three-point drilling and milling cutter, relatively speaking, did not exhibit excessive burrs and tearing. Overall, the cylindricity of the holes was not particularly high, showing a better statue than Fig. 8 (a), while a worth one than Fig. 8 (b). However, noticeable layering phenomena were observed, as shown in Fig. 8 (c). (2) Analysis of maximum mean thrust force Since thrust force is a crucial factor leading to defects at the hole exit, the maximum thrust force measured during the drilling process under various parameters is selected for analysis when comparing the drilling forces of different tool structures. This measurement is used as an assessment of the drilling performance of each tool. The three plots depicting the maximum thrust force are presented in Fig. 9 during the drilling process with the new tools under various process parameters. A strong correlation between process parameters and thrust force by the dagger drill was observed, as shown in Fig. 9 (a). The maximum thrust force strictly decreased with the increase in spindle rotation speed and strictly increased with the augmentation of feed rate. The general variation trend of the thrust force of the three-point twist drill and the three-point drilling and milling cutter with the process parameters was similar to that of the dagger drill, as shown in Fig. 9 (b) and Fig. 9 (c). Slightly different from the dagger drill, little change was observed in the thrust force of the three-point twist drill when the feed speed was 40mm/min, irrespective of the spindle rotation speed. Similarly, for the three-point drilling and milling cutter, little variation in the maximum thrust force was noted within the larger spindle rotation range when the feed speed was 50 or 60mm/min. Above all, the overall variation trend of the thrust force for the three-point twist drill and the three-point drilling and milling cutter was similarly to that of the dagger drill with respect to process parameters, as shown in Fig. 9 (c). Slight deviations from the dagger drill were observed, wherein, for the three-point twist drill, minimal variations in thrust force occurred with changes in spindle rotation speed at a feed rate of 40 mm/min. Similarly, for the three-point milling cutter, at feed rates of 50 and 60 mm/min, within larger spindle rotation speed ranges, the maximum thrust force exhibited minimal changes. (3) Measurement of damage factors of synthetic pre-drilled hole For a comprehensive and rational quantification of various hole exit damages on BCF/PEEK specimens after drilling, and further analysis of the perforation quality of different tools under various process parameters, a pre-drilled hole’s damage comprehensive evaluation method proposed by Liu et al. [ 29 ] was adopted in this study. Based on the structure of BCF/PEEK, a comprehensive assessment of perforation damage was conducted, with consideration given to burr formation, tearing, and delamination as three aspects for evaluation. Regarding burr damage, minor burrs with lengths less than 0.2mm are initially disregarded, as their impact on the actual assembly quality of the hole is relatively insignificant. For longer burrs with lengths exceeding 0.2mm, different evaluation criteria are applied based on the width of the burr. When the burr width is less than 0.1mm, its length is utilized for characterization, whereas for burrs with widths greater than 0.1mm, characterization is performed using the area method. The burr damage coefficient D b is defined as. $${D}_{b}=\alpha \frac{2\sum _{i=1}^{n}{L}_{i}}{d}+\beta \frac{4\sum _{j=1}^{m}{A}_{j}}{\pi {d}^{2}}$$ (1) where, \(\sum _{i=1}^{n}{L}_{i}\) represents the length and sum of fine burrs that are not cut off around the hole. \(\sum _{j=1}^{m}{A}_{j}\) represents the sum of the total area of the wide burr; d stands the diameter of the hole; α and β represent the weight factors of fine burrs and wide burrs affecting the quality of the hole, respectively. α = 0.2, β = 0.8 are adopted in this study. Regarding tearing damage, it is primarily defined as damage with a certain width and is commonly characterized using area parameters. The characterization principle involves the establishment of a criterion where the tearing length should not exceed three times the hole diameter, and the width should be less than 1.8mm. The tear damage coefficient D t is defined as. $${D}_{t}=\frac{\sum _{k=1}^{l}{A}_{k}}{4.8d}$$ (2) where, \(\sum _{k=1}^{l}{A}_{k}\) represents the cumulative area of small part of the tear, k = 2 is adopted in this study. For exit delamination damage, the evaluation metric involves measuring the area of the delamination region, and the lamination damage coefficient D d at the exit is defined as. $${D}_{d}=\frac{4{A}_{d}}{\pi {d}^{2}}-1$$ (3) where, A d represents the total area of the delamination zone. When evaluating individual forms of damage, the reflection of bore quality remains unidimensional, resulting in significant randomness in the analysis results. Therefore, the composite influence of diverse damages on bore quality needs to be considered. Weighting factors are consequently assigned to the respective damage coefficients, leading to the derivation of a comprehensive damage factor denoted as D , expressed as follows. $$D={w}_{1}\left(\alpha \frac{2\sum _{i=1}^{n}{L}_{i}}{d}+\beta \frac{4\sum _{j=1}^{m}{A}_{j}}{\pi {d}^{2}}\right)+{w}_{2}\left(\frac{\sum _{k=1}^{l}{A}_{k}}{4.8d}\right)+{w}_{3}\left(\frac{4{A}_{d}}{\pi {d}^{2}}-1\right)$$ (4) where, w 1 , w 2 and w 3 respectively represent the weight factors of burr, tear and delamination damage on drilled hole quality. According to the study on the change rule of damage coefficient caused by tool wear in the drilling process of Wen et al. [ 30 ], the values of w 1 , w 2 and w 3 are 1, 1.5 and 4 in this study, respectively. To further analyze the drilling characteristics of various drill bit structures and identify the tool structure that exhibited optimal performance in controlling delamination damage, a lateral comparison of the comprehensive borehole damage factors for different drill bit structures was conducted under multiple process parameters, as shown in Fig. 10 . The comprehensive borehole damage factors were compared, and it was observed that the dagger drill exhibited the lowest borehole damage factors across all process parameters, as depicted in the four plots. The borehole damage factors for the dagger drill were consistently found to be at least 15% lower compared to the other two drill bit structures. The most significant disparity was observed at n = 5000r/min, f = 30mm/min, where the borehole damage factor for the dagger drill was 51.3% lower than that of the twist drill. Furthermore, minimal fluctuation in the borehole damage factor of the dagger drill was observed with variations in process parameters. The outstanding performance displayed by the dagger drill in ensuring bore quality was consistently maintained within 1.14 across all machining parameters. The borehole damage factor of the three-point drill-milling cutter was generally ranked just below that of the dagger drill, but the difference was substantial, ranging from 1.25 to 1.43. Considerable fluctuations in the damage factor were observed with variations in process parameters. For the three-point drill-milling cutter, after considering machining quality, the optimal processing parameters were determined to be n = 4000r/min, f = 30mm/min, resulting in a corresponding damage factor of 1.252. On the other hand, the borehole damage factor of the three-point twist drill was generally the highest across all parameters, with the maximum reaching up to 1.648. The borehole quality was the poorest, and it was significantly influenced by variations in spindle rotation speed. Therefore, the three-point twist drill was deemed unsuitable for precision machining of BCF/PEEK. According to the analysis of hole exit morphology, the best borehole quality was achieved with the dagger drill, followed by the three-point drilling bit and milling cutter, while relatively poorer borehole quality was exhibited by the three-point twist drill. 4. Drilling damage prediction considering process parameters using tapered drill-reamer From the experimental research and analysis in section 3 , it can be concluded that there is a strong correlation between thrust force and process parameters. Furthermore, delamination damage at the borehole exit is primarily caused by thrust force. Therefore, in order to predict borehole quality under specific process parameters, it is crucial to investigate the relationship between the damage factor and process parameters. Consequently, the derived relationship enables a quantitative prediction of the damage factor. 4.1 Defect analysis based on damage factors The regression analysis method is employed to ascertain whether a correlation exists between two or more sets of data by utilizing statistical principles. In this manner, the relationship between the dependent and independent variables is determined, and variations in the dependent variable can be predicted under different conditions of independent variables using this method. Since the reason that delamination damage is primarily caused by thrust force, delamination phenomena are likely to occur when a certain threshold of thrust force is reached. The relationship between damage factors and thrust force can be investigated through the application of regression analysis. Consequently, the regression equation for this relationship can be derived, enabling the prediction of the delamination extent for other parameters. The focus of this section is on the dagger drill, which is considered the optimal drilling tool for achieving high-quality holes among the three tools examined. A quantitative analysis of composite drilling damage was conducted, and the drilling damage factors of the dagger drill for various process parameters are presented in Table 5 . Table 5 The damage factors of the dagger drill Num. n / (r/min) f / (mm/min) F /(N) D Num. n / (r/min) f / (mm/min) F /(N) D 1 2000 30 128 1.087 9 4000 30 101.8 1.105 2 2000 40 143.6 1.134 10 4000 40 109.3 1.138 3 2000 50 161.3 1.130 11 4000 50 119.6 1.118 4 2000 60 171 1.084 12 4000 60 138.7 1.079 5 3000 30 110 1.058 13 5000 30 90 1.089 6 3000 40 127.4 1.087 14 5000 40 105.9 1.107 7 3000 50 138 1.116 15 5000 50 115.2 1.090 8 3000 60 147.8 1.076 16 5000 60 134.5 1.132 After qualitatively comparing the data presented in Table 5 , it was observed that the overall trend indicates an increase in the damage factor with the escalation of thrust force. However, a deviation from this general trend was noted in the tenth set of data, where the maximum damage factor among all holes was obtained under relatively low thrust force conditions. This deviation, contrary to the overall trend, lacked analytical value. The underlying reason for this anomaly may be attributed to the uneven thickness of the BCF/PEEK specimen during the preparation process, resulting in insufficient bonding strength between layers in certain regions. Consequently, severe delamination phenomena were more prone to occur during the drilling process in these areas. After excluding the tenth set of data, the remaining fifteen sets of data were imported into MATLAB software in the form of scatter plots. By conducting fitting, a regression equation between the damage factor and the maximum thrust force was derived. The fitted function is graphically represented in Fig. 11 . According to the graph of the fitted function, it could be distinctly observed that a robust relationship existed between the maximum thrust force and the damage factor, and the thrust force was amplified with the damage factor increasing. The equation derived from the fitting process can be written as. $${F}_{d}\text{= 471000-34500}F\text{+1115}{F}^{2}\text{-21}{F}^{3}\text{+0.25}{F}^{4}\text{-0.002}{F}^{5}\text{+}{F}^{6}*{10}^{-5}$$ (5) where, \({F}_{d}\) is damage factor. F is maximum thrust force. 4.2 Multiple regression model of process parameters and thrust force Through the analysis of the data from the aforementioned experiments in section 3 , it was evident that a strong correlation exists between the thrust force of the dagger drill and the feed rate or spindle rotation speed. To quantitatively analyze the relationship between thrust force and process parameters, a multiple regression model was established, with the feed rate ( f ) and spindle rotation speed ( n ) as independent variables, and the maximum thrust force ( F ) as the dependent variable. The model equation formulated can be written as. $$F=C{n}^{i}{f}^{j}$$ (6) where, C, i and j denote constants. For ease of solution, taking the logarithm of both sides of Eq. (5) results in Eq. (6), thereby transforming the nonlinear problem into a linear problem for analysis. $$InF=InC+iInn+jInf$$ (7) During the actual solving process, the first fifteen sets of data from Table 5 were imported into MATLAB software for fitting and calculating the model. The sixteenth set of data was reserved for validating the effectiveness of the model. The fitting equation was obtained as. $$InF=6.11156-0.36075Inn+0.43508Inf$$ (8) Three parameters were calculated as follows: C = 451, i =-0.36075, j = 0.43508. The regression equation of the maximum thrust force was obtained by substituting the obtained parameter values back into Eq. (5). $$F=451{n}^{-0.36075}{f}^{0.43508}$$ (9) where, the unit of F is N , the unit of n is r/min, and the unit of f is mm/min. Table 6 Summary of fitting statistics In C i j Statistics Value Standard error Value Standard error Value Standard error Adjusted R 2 6.11156 0.16225 -0.36075 0.0163 0.43508 0.02165 0.98622 Table 7 The thrust force regression model test Model DOF Squares Square-mean Value of F significance level Probability> F Regression 2 0.44715 0.22357 502.0307 0.05 2.713×10 − 12 Residual 12 0.00534 4.453×10 − 4 Sum 14 0.45249 The summary of the relevant statistical values of the regression obtained by fitting is shown in Table 6 . When taking the significance level α = 0.05, the calculated R 2 was 0.98622. The thrust force regression model test is presented in Table 7 , where F = 502.0307, and the probability greater than F was only 2.713×10 − 12 , indicating a better fitting effect. Substituting spindle rotation speed n = 5000r/min and feed speed f = 60mm/min from the 16th set of data in Table 5 into the regression equation formula, a calculated predicted value of F = 124 N was obtained. Comparing this value with the real measured value of 134.5 N , the error was only 8.5%, indicating that the regression model could predict the maximum thrust force in the drilling process with two-factor variation more accurately. From the expression of the regression equation, it also could be observed that the spindle rotation speed and feed rate interact to influence the maximum thrust force. By increasing the spindle rotation speed and decreasing the feed rate, the thrust force can be effectively reduced. 4.3 Prediction and verification of drilling damage under different parameters Previously, the fitting Eq. (4) for the relationship between the damage factor and the maximum thrust force was obtained through a univariate regression. In this chapter, the fitting Eq. (9) expressing the relationship between the maximum thrust force, spindle rotation speed, and feed rate was derived using bivariate regression. The relationship between the damage factor \({F}_{d}\) and the two process parameters was obtained by substituting Eq. (9) with Eq. (4). $${F}_{d}\text{= 471000-34500}*\left(451{n}^{-0.36075}{f}^{0.43508}\right)\text{+1115}{F*\left(451{n}^{-0.36075}{f}^{0.43508}\right)}^{2}$$ $$\text{-21}{*\left(451{n}^{-0.36075}{f}^{0.43508}\right)}^{3}\text{+0.25}{\left(451{n}^{-0.36075}{f}^{0.43508}\right)}^{4}$$ $$\text{-0.002}{451{n}^{-0.36075}{f}^{0.43508}}^{5}\text{+}{451{n}^{-0.36075}{f}^{0.43508}}^{6}*{10}^{-5}$$ (10) The relationship and impact patterns between spindle rotation speed, feed rate, and damage factor during the drilling process with dagger drills were explicitly articulated in Eq. (10). It could be quantitatively observed from the formula that the layering degree of the hole outlet can be effectively reduced, and the quality of the hole can be improved by selecting perforating process parameters with spindle rotation speed and low feed rate. On one hand, the relationship between the damage factor and the process parameters can be utilized to predict the damage factor of the hole drilled under known process parameters and characterize the quality of hole formation. On the other hand, suitable process parameters for the drilling process can be chosen to attain a specific quality, which holds significant practical value and significance. To assess the predictive capability of the model for the comprehensive damage factor, two additional sets of process parameters were selected and substituted into Eq. (9). The model's predicted damage factor values were then computed. Subsequently, drilling experiments were conducted under these two sets of process parameters, and the actual damage factor values were observed and calculated. A comparative analysis was then undertaken between the predicted and experimental values to analyze the prediction errors. Two groups of extreme and exceptional process parameters are as follows: (1) Spindle rotation speed n = 1000r/min, feed speed f = 70mm/min; (2) Spindle rotation speed n = 6000r/min, feed speed f = 20mm/min. Three holes were drilled under each group of process parameters, and the average value of the damage factors for the three holes was taken as the actual damage factors under the group of process parameters. Figure 12 presents the data of experimental damage factors and predicted damage factors, while it is also depicted the comparative analysis chart of drawing errors. From the experimental results, it could be observed from the chart that the real damage factor value of experiment, conducted with low feed rate and high spindle rotation speed, was slightly larger than the predicted value calculated by Eq. (10), with an error of 0.276%. Conversely, under the condition of high spindle rotation speed and low speed rate, the actual damage factor value is slightly smaller than the predicted value, with a margin of error of 0.444%. These results indicate that the established model can accurately predict the comprehensive damage factors of dagger drilling outlets, highlighting its valuable application potential. 5. Conclusion This paper presents a novel method for selecting optimal drilling tools and damage prediction analysis in BCF/PEEK drilling. Firstly, a comprehensive analysis is conducted on the reasons behind drilling damage defects caused by traditional twist drills using a scale-span FE model based on modified micromechanics of failure criterion with new damage evolution laws. Subsequently, the causes of damage defects in prefabricated holes resulting from twist drills are investigated through simulation results, and the accuracy of the simulation model is validated through corresponding experiments. Following this, three innovative types of drilling tools are designed, and orthogonal experiments on BCF/PEEK drilling are conducted. Data on hole exit morphology, thrust force, and damage factors are systematically collected and observed, enabling a comprehensive comparative analysis of the drilling performance of each tool. Lastly, a process parameters-oriented drilling damage prediction method is introduced. Regression models for damage factor and thrust forces, as well as thrust force and process parameters, are respectively established, with thrust force serving as the intermediate variable. The regression equations are derived through fitting and solving, elucidating the relationship between damage factor and process parameters. Based on the above research, the following conclusions can be drawn. (1) The preliminary experimental findings demonstrate that the scale-span FE drilling model can accurately simulate various defects during BCF/PEEK drilling. The analysis reveals that the maximum thrust force can still exceed 400N. Drilling experiments with a traditional twist drill under identical process parameters indicate the presence of numerous burrs and delamination damage at the hole outlet, resulting in suboptimal hole quality. (2) The thrust force during drilling with the dagger drill is consistently more than one-third smaller than that of the two three-point drills, leading to minimal damage at the hole exit. Regardless of process parameters, the hole exit damage factor remains below 1.14, significantly outperforming the two three-point drills and ensuring superior hole quality. (3) Multiple nonlinear regression analyses are conducted to establish an equation describing the relationship between thrust force, spindle speed, and feed rate. At a significance level of α = 0.05, the coefficient of determination is found to be 0.98622, indicating a high degree of goodness of fit. This analytical approach not only establishes the correlation between the damage factor and process parameters but also validates the model's robustness in capturing the intricate relationships within the machining process. (4) The maximum error is 0.276% at high spindle rotation speed and low feed rate, and 0.444% at high feed rate and low spindle rotation speed, affirming the accuracy of the method. Using thrust force as an intermediary parameter, a regression equation describing the relationship between thrust force and the damage factor is derived through simple nonlinear regression. Declarations Acknowledgements The authors would like to acknowledge the editors and the anonymous referees for their insightful comments. Ethical approval This article does not contain any studies with human participants performed by any of the authors. Consent to participate Work was conducted with no human test subjects. Consent to publish Work has consent to publish. Authors’ contributions Yong Liu designed the study, performed the research, analysis data, and wrote the paper. Shenao Zhu and Guangyao Xu conducted experiments and data processing. Meng Zhu provided simulation experimental data and designed the drilling tool bit. Zitao Pan modified the paper. Funding The work reported herein is sponsored by the National Natural Science Foundation of China (52105450), the University Science Research Project of Jiangsu Province (No. 21KJB460016). The authors would like to acknowledge the editors and the anonymous referees for their insightful comments. Competing interests Authors declare that they have no competing interests. Availability of data and materials The experimental and simulation data is transparency. References Zeng J J, Yan T Z, Jiang Y Y, et al. 3D printing of FRP grid and bar reinforcement for reinforced concrete plates: Development and effectiveness. Composite Structures, 2024, 335 117946. Xing L, Jian F W, Heng C B, et al. 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Cite Share Download PDF Status: Published Journal Publication published 05 Mar, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Editorial decision: Major Revisions Needed 27 Aug, 2024 Reviewers agreed at journal 31 May, 2024 Reviewers invited by journal 29 May, 2024 Editor assigned by journal 29 May, 2024 First submitted to journal 26 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4480703","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":308221475,"identity":"cec46370-7776-47e3-b0ad-92b2a15dddea","order_by":0,"name":"Yong 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15:52:46","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4480703/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4480703/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00170-025-15303-6","type":"published","date":"2025-03-05T15:57:44+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":58122711,"identity":"6ebf60e2-f689-42f5-ac42-864018815968","added_by":"auto","created_at":"2024-06-11 12:25:49","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":1977550,"visible":true,"origin":"","legend":"\u003cp\u003eThe scale-span FE model of drilling BCF/PEEK using a twist drill\u003c/p\u003e","description":"","filename":"Fig.1.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/dbf94719998e416efb7eba7d.png"},{"id":58122696,"identity":"d88a274c-527c-4475-9261-2b9ee20c4110","added_by":"auto","created_at":"2024-06-11 12:25:48","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":3686628,"visible":true,"origin":"","legend":"\u003cp\u003eComprehensive experimental system of drilling process monitoring\u003c/p\u003e","description":"","filename":"Fig.2.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/7cd3a942245cf1b8a09a6fb2.png"},{"id":58122702,"identity":"c8fade20-72c2-4cd8-ae83-b270e7288c0f","added_by":"auto","created_at":"2024-06-11 12:25:48","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":2826356,"visible":true,"origin":"","legend":"\u003cp\u003eObservation procedure of holes with different process parameters\u003c/p\u003e","description":"","filename":"Fig.3.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/4e5e09ad4cda0941560c0beb.png"},{"id":58122718,"identity":"dc8b3d54-a4e3-4188-aed3-d439e9e9228c","added_by":"auto","created_at":"2024-06-11 12:25:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":1966811,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of hole’s damage between scale-span FE model and experiment\u003c/p\u003e","description":"","filename":"Fig.4.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/698c51a16d650bd16b983207.png"},{"id":58122715,"identity":"02527125-8e55-45c3-ad3d-eab8e122ccef","added_by":"auto","created_at":"2024-06-11 12:25:49","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1025863,"visible":true,"origin":"","legend":"\u003cp\u003eDifferent types of drill design\u003c/p\u003e","description":"","filename":"Fig.5.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/50d3512191965f7fffd3cca1.png"},{"id":58123091,"identity":"cd5b60b7-a04e-4e6c-971c-5aa2ca077b11","added_by":"auto","created_at":"2024-06-11 12:33:49","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":497181,"visible":true,"origin":"","legend":"\u003cp\u003eThe structural parameters of different drilling bits\u003c/p\u003e","description":"","filename":"Fig.6.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/01c107c6000feefe4ba3ce79.png"},{"id":58122717,"identity":"27ae1c5d-235e-4189-b8b9-ca7655420a26","added_by":"auto","created_at":"2024-06-11 12:25:49","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":931897,"visible":true,"origin":"","legend":"\u003cp\u003eThe experimental diagram for drilling scheme\u003c/p\u003e","description":"","filename":"Fig.7.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/1c64089e476b592ebb8939c4.png"},{"id":58123092,"identity":"afd02bd2-adb6-4115-864e-b523192f2735","added_by":"auto","created_at":"2024-06-11 12:33:49","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":1882832,"visible":true,"origin":"","legend":"\u003cp\u003eThe exit morphology of the drilled holes\u003c/p\u003e","description":"","filename":"Fig.8.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/e748c0386210591f4370bfee.png"},{"id":58123090,"identity":"9fb436ae-47ed-493e-8bba-985f140ca9d0","added_by":"auto","created_at":"2024-06-11 12:33:49","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":747902,"visible":true,"origin":"","legend":"\u003cp\u003eThe maximum thrust force of different tools under multiple process parameters\u003c/p\u003e","description":"","filename":"Fig.9.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/c8fb2ccd3c29d751945a2d33.png"},{"id":58122700,"identity":"635e5c08-22de-4cc6-944e-d075e68778eb","added_by":"auto","created_at":"2024-06-11 12:25:48","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":1122733,"visible":true,"origin":"","legend":"\u003cp\u003eDamage factors of each bit structure under multiple process parameters\u003c/p\u003e","description":"","filename":"Fig.10.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/d5cfd727b3c47f6aea80b656.png"},{"id":58122713,"identity":"c20e7765-ece1-405f-b034-7f6a193a8054","added_by":"auto","created_at":"2024-06-11 12:25:49","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":133454,"visible":true,"origin":"","legend":"\u003cp\u003eRegression curve of maximum thrust force and damage factor\u003c/p\u003e","description":"","filename":"Fig.11.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/f1651ef1ac42e0451a30c8b3.png"},{"id":58122720,"identity":"67ee7e9c-12ca-4651-acb1-d743b513b12c","added_by":"auto","created_at":"2024-06-11 12:25:50","extension":"png","order_by":12,"title":"Figure 12","display":"","copyAsset":false,"role":"figure","size":816543,"visible":true,"origin":"","legend":"\u003cp\u003eComparative analysis and error between predicted results and experiment\u003c/p\u003e","description":"","filename":"Fig.12.png","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/8a0e2469ef89c0d170167d28.png"},{"id":78191344,"identity":"fda3ce6c-4828-4a64-9b1f-b150e8a73af4","added_by":"auto","created_at":"2025-03-10 19:56:37","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":26205107,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4480703/v1/4c312bda-3a3d-4914-a76b-2e6a4150ec81.pdf"}],"financialInterests":"","formattedTitle":"A Novel Method for Damage Prediction in BCF/PEEK Drilling Using an Innovative Drill Tool","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eCarbon fiber reinforced thermoplastic plastics (CFRTP) constitutes a novel class of composites manufactured through intricate processes such as impregnation and molding, utilizing high-temperature-resistant resin as the matrix and high-performance carbon fiber filaments as the reinforcement [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. In comparison to carbon fiber-reinforced plastic (CFRP), CFRTP offers notable advantages, including enhanced corrosion resistance, lightweight, rapid and cost-effective manufacturing, as well as recyclability [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Poly ether ether ketone (PEEK) is an outstandingly versatile specialty engineering plastic, characterized by exceptional heat resistance, resistance to hydrolysis, excellent chemical resistance, electrical insulation properties, and radiation resistance, especially when braided carbon fiber and PEEK resin are combined to form braided carbon fiber reinforced poly ether ether ketone (BCF/PEEK). These attributes ensure dimensional stability in extreme environments, which has garnered extensive attention in the civil aviation sector [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. For instance, PEEK is utilized by Boeing Corporation in the injection molding process to manufacture engine nacelles for the B757. This composite demonstrates resilience under harsh conditions, resulting in a weight reduction of approximately 30% compared to aluminum alloy or titanium alloy products, accompanied by a cost reduction of around 90% [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Additionally, PEEK has been employed by Stelia Corporation to manufacture a full-scale thermoplastic fuselage demonstrator, aimed at assessing the feasibility of using thermoplastic composites in the next generation of single-aisle aircraft [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe predominant method for composite structure assembly in the aerospace manufacturing industry is composed by mechanical connections, represented by rivets and bolts [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Substantial drilling and hole-making operations are involved in the riveting and bolting processes, and the tensile strength and fatigue damage of structural components are significantly influenced by high-quality hole-making[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. The drilling of CFRTP using conventional cutting tools is susceptible to processing damage such as tearing, burrs, and delamination at hole exits [\u003cspan additionalcitationids=\"CR10\" citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]-[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], thereby compromising the reliability of the product. The traditional twist drill exhibits a relatively long transverse cutting edge, and during the drilling process of composites, approximately 60% of the total thrust force is generated by the transverse edge, thereby leading to the occurrence of delamination at hole exits [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. A drilling experiment on carbon fiber composite was conducted by Qiu et al [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e], and the results showed that traditional twist drilling could not achieve high-quality drilling, while step drilling could improve the quality of hole making. The quality of drilling can also be directly affected by the selection of process parameters [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The influence of drilling process parameters on the delamination damage of carbon fiber composite was analyzed by Gaitonde et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] through experimental research, and they found that stripping delamination of holes can be reduced when high-speed machining is carried out. Therefore, reasonable drilling tool selection and process parameter optimization are the main methods to achieve high-quality hole making of thermoplastic composites.\u003c/p\u003e \u003cp\u003eCurrently, research on hole-making in composites primarily focuses on two aspects. one involves the investigation of drilling tools, and the other entails the optimization and prediction of drilling process parameters. Extensive research has been conducted on the characteristics of drilling composites using various structural tools, with significant manifestations evident in both research methodologies and outcomes. For instance, drilling experiments with different spindle rotation speeds and feed rates were conducted by Wang et al. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] comparing the influence of different drilling methods on hole quality. The results showed that drilling with a ladder bit produced less thrust, less delamination damage, and the highest hole-making quality. A new auger cutting tool was proposed by Kong et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] to replace the traditional auger end milling cutter, realizing auger drilling and reaming processing, and effectively inhibiting the drilling damage of composite laminates. PCD twist drills and special diamond-coated double-tip drills were used by Al-wandi et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] to carry out drilling experiments on composites, and the results were verified through FE analysis, concluding that double-tip drilling resulted in higher hole quality. Using the Box-Behnken design method, Palanikumar et al. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] conducted experiments to establish the empirical relationship of GFRTP thrust force and analyzed the factors and functions affecting drilling in detail. Through experiments, Mudhukrishnan et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] concluded that borehole quality was better when the spindle rotation speed was 2500r/min and the feed speed was 0.05mm/r. Regression models of borehole surface roughness and aperture error were established respectively using the experimental data, with a very strong correlation observed. Feito et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] utilized a simplified model to study the effects of thrust force, laminate bottom clamping area, and laminate sequence on delamination damage during the drilling of carbon fiber-reinforced composite. The calculation cost was low, but the predicted value of the delamination factor was slightly higher. A mathematical model of the relationship between processing parameters and delamination damage was established by Mudhukrishnan et al. [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e], obtaining an empirical relationship that can better predict delamination damage during composite drilling.\u003c/p\u003e \u003cp\u003eRegarding scholars studying CFRP drilling, plentiful studies have extensively focused on the laminated structures of thermoset composites. While some research on woven structures exists, the damage mechanisms and mechanical behavior during the processing of CFRTP significantly differ from those of CFRP [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e], thereby imposing certain limitations on the research. Meanwhile, research on CFRTP is also influenced by its manufacturing processes, with the current emphasis predominantly placed on laminated structures. The existing research on drilling CFRTP has not systematically analyzed the shortcomings of traditional drilling tool structures. Moreover, the research in this area is relatively singular, and when it comes to drilling experiments using novel drilling tools, there is a lack of cross-tool comparison in terms of drilling quality, rendering the obtained data relatively incomplete. Additionally, there is relatively limited research on the subsequent processing and in-depth analysis of drilling data. Determining pre-drilled hole\u0026rsquo;s quality under real process parameters still necessitates specific drilling experiments, entailing significant investments in terms of manpower and time costs. Most existing predictive models primarily conduct analytical predictions under individual process parameters (such as spindle rotation speed or feed rate) and lack effective experimental validation.\u003c/p\u003e \u003cp\u003eAddressing certain issues identified in the preceding studies, this study proposes a method to optimize drilling tools and damage prediction analysis in BCF/PEEK drilling. Initially, a scale-span drilling FE model of BCF/PEEK employing a twist bit is developed based on modified micromechanics of failure criterion with new damage evolution laws. The causes of damage defects in prefabricated holes induced by twist drills are analyzed, and the accuracy of the simulation model is validated through experiments. Subsequently, three types of innovative tools are devised, and orthogonal experiments on drilling BCF/PEEK are conducted. Exit orifice morphology, thrust force, and damage factors are meticulously observed and recorded, facilitating a comparative analysis of the drilling performance of each tool. Then, by utilizing thrust force as the intermediate variable, regression models are established separately for the relationships between damage factors and thrust force, as well as between thrust force and process parameters. Regression equations for each relationship are derived through fitting. Furthermore, the correlation between the damage factor and process parameters is determined, and a hierarchical damage prediction method oriented towards process parameters is proposed. Two groups of extreme and exceptional process parameters are validated through the corresponding experiments.\u003c/p\u003e"},{"header":"2. Damage mechanism analysis on drilling BCF/PEEK using twist drill","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Scale-span FE analysis of twist drill drilling\u003c/h2\u003e \u003cp\u003eA drilling scale-span FE model for BCF/PEEK using a twist drill was developed on the ABAQUS/Explicit software platform in this study. The twist drill bit model was created in SolidWorks software based on the geometric parameters of the drill's solid structure and then imported into ABAQUS for implementation. Following our prior research [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], the three-dimensional model structure of BCF/PEEK was defined using the VUMAT subroutine to incorporate internal damage formulation via the proposed dynamic three-dimensional scale-span model, which is based on a modified micromechanics of failure criterion with new damage evolution laws. Material removal simulation during cutting action was accomplished using methods such as element stiffness degradation and removal. Additionally, a failure analysis model of cohesive elements (CEs) based on a mixed-mode failure criterion [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] was established within the braided structure of BCF/PEEK to simulate delamination phenomena that occur during the drilling process. Furthermore, the length of the cohesive elements zone was selected to be approximately 2\u0026ndash;3 times the length of an element side, chosen to regularize the delamination fracture toughness and mitigate mesh sensitivity.\u003c/p\u003e \u003cp\u003eAccording to the above description, the comprehensive scale-span simulation model for drilling BCF/PEEK is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, which is encompassing the configuration of boundary conditions and the structural parameter of the twist bit.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe focus of this study is mainly investigating the scale-span analysis of BCF/PEEK in the entire drilling process, with the research subject being a CFRTP composed of 6K Toray T800S carbon fibers and a high-temperature resistant resin, denoted as BCF/PEEK. The density of prepreg is 200g/m\u003csup\u003e2\u003c/sup\u003e. Utilizing a braided structure, the overall dimensions of the BCF/PEEK laminate were 14.70mm\u0026times;14.70mm\u0026times;4.05mm, comprising a total of 32 layers. To achieve a comprehensive and accurate prediction of thrust force and torque during the drilling process, the twist drill with a 6mm diameter (coated with AlTiN) was modeled as a discrete rigid body.\u003c/p\u003e \u003cp\u003eThe total mass and rotational inertia of the twist drill were constrained at the top reference point. Boundary conditions were applied based on this reference point, including the feed rate and rotation speed of the drill bit. To enhance computational efficiency and conserve computational resources, mesh refinement was applied to the drilling contact region of the BCF/PEEK laminated plate (a circular area with a diameter of 10mm). Meanwhile, coarser meshes were employed in the vicinity of the laminate edges and the twist drill to optimize the simulation. The BCF/PEEK is modeled using C3D8RT elements, which are 8-node, three-dimensional reduced integration elements. The twist drill was represented using C3D8RT discrete rigid body elements. In accordance with the actual machining conditions, where the drill was fed along the Z direction into the BCF/PEEK, boundary conditions such as rotation speed and feed rate were applied to the entire drilling FE model. Since the motion state of the twist drill model was constrained at the top reference point, displacements in the X and Y directions at the reference point were restricted, while a feed velocity was applied in the Z direction. Similarly, rotational speeds in the X and Y directions were constrained, a clockwise rotational velocity was imposed in the Z direction, and the four vertical surfaces of BCF/PEEK were fixed.\u003c/p\u003e \u003cp\u003eTo simulate the occurrence of burrs during the drilling process, the mesh size of the BCF/PEEK elements needed to be on the scale of the fiber bundles. Based on the optimization analysis of the sensitivity model for element mesh, the entire scale-span drilling FE model comprised a total of 235,420 elements. This included 235,200 hexahedral elements for the BCF/PEEK and 220 tetrahedral elements for the twist drill. The minimum size of the BCF/PEEK elements was approximately 208\u0026times;208\u0026times;83\u0026micro;m. In the predefined global coordinate system, a transversely isotropic material, namely UD-PEEK, was assigned to the single fiber bundle of BCF/PEEK along the fiber direction. Among them, the unidirectional paving structure parameters of BCF/PEEK are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e, and the attribute parameters of CEs are shown in Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe unidirectional prepreg material property parameters of BCF/PEEK\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003ePerformance index\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003ePerformance index\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe areal-density of prepreg fiber (g/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e160\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eElongation of carbon fiber\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2%\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe areal-density of the prepreg (g/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e242\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThe density of carbon fiber (g/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.8\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThe density of BCF/PEEK (g/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e1.57\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eThe density of PEEK\u003c/p\u003e \u003cp\u003e(g/m\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1.35\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTensile strength of carbon fiber (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e4900\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBending strength of PEEK (MPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e150\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTensile modulus of carbon fiber (GPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e230\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eBending modulus of PEEK (GPa)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe material property parameters of CEs\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eStiffness\u003c/p\u003e \u003cp\u003eparameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eValue (N/mm\u003csup\u003e3\u003c/sup\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eStiffness parameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eValue (MPa)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eFracture energy\u003c/p\u003e \u003cp\u003eparameter\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eValue (N/mm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e4\u0026times;10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eδ\u003c/em\u003e\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003en\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e=K\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c2\"\u003e \u003cp\u003e1\u0026times;10\u003csup\u003e6\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eδ\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e\u0026thinsp;\u003cem\u003e=\u0026thinsp;δ\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eG\u003c/em\u003e\u003csub\u003e\u003cem\u003es\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e=G\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe entire scale-span FE model had been subjected to a complete factorial design employing three levels for the machining parameters [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Specifically, the twist drill spindle rotation speeds (\u003cem\u003eSr\u003c/em\u003e) of 2000 rpm, 3000 rpm, and 4000 rpm, as well as the feed rates (\u003cem\u003eSf\u003c/em\u003e) of 0.01 mm/rev, 0.02 mm/rev, and 0.03 mm/rev, were respectively applied within the model. In order to analyze the damage incurred by twist drills with different parameters on BCF/PEEK models with varying ply orientations, a scale-span FE model was developed. The contact behavior between the drill bit and BCF/PEEK was simulated using a penalty-based Coulomb friction model. A friction coefficient of 0.3 was applied in the normal direction of the contact. The face-to-face contact between the twist drill and the BCF/PEEK model was implemented using explicit dynamics, wherein the twist drill surface nodes interacted with the BCF/PEEK element nodes. The twist drill surface was designated as the master surface in the contact configuration. To save computational time, only the central circular region with a diameter of 10mm and its interior within the BCF/PEEK material were defined as facets (formed based on element nodes).\u003c/p\u003e \u003cp\u003eBased on the aforementioned settings, jobs were created and the corresponding calculation input file was output to check for errors. The mass scaling factor was set to 10\u003csup\u003e3\u003c/sup\u003e according to the reference [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] to improve computational efficiency on the premise of ensuring accuracy through many attempts. The complete computation of a job required approximately 163 hours on a high-performance computer with two 48 core 8180M platinum processors and 128 GB RAM. All simulations were performed at the high-performance computing facility at Jiangsu University of Science and Technology.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Damage mechanism analysis and experimental verification\u003c/h2\u003e \u003cp\u003eAfter preparation and mechanical properties testing, the BCF/PEEK workpieces were transformed into drilling specimens by cutting according to the design of a special fixture, and at least two drilling test specimens of each type were required to ensure the accuracy of test results. Meanwhile, a suitable experimental platform based on the vertical machining center for drilling experiments was established.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe whole experimental platform consists of the thrust force data acquisition module and temperature data acquisition module. The experiment was conducted on the CNC machinery DX-650 vertical machining center. The spindle rotation speed of the machine tool could reach up to 30000r/min, the main motor power was 5.5kW, and the positioning accuracy was 0.005mm, and the schematic diagram of the experimental platform and the connection relationship of each part is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. Meanwhile, the heat generated during drilling of composite is prone to causing thermal damage to the composite. Therefore, the FPR-A615 infrared thermal imager was utilized, which had a thermal sensitivity of \u0026lt;\u0026thinsp;0.05\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(℃\\)\u003c/span\u003e\u003c/span\u003e and an accuracy of \u0026plusmn;\u0026thinsp;2\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(℃\\)\u003c/span\u003e\u003c/span\u003e, and the measuring range could reach \u0026minus;\u0026thinsp;40\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(℃\\)\u003c/span\u003e\u003c/span\u003e to 2000\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(℃\\)\u003c/span\u003e\u003c/span\u003e, effectively fulfilling the function of temperature monitoring. In addition, the data of thrust force and torque were collected by the Kistler-9129AA dynamometer. The sampling frequency was 5000Hz, and the sampling time was set to 45\u003cem\u003es\u003c/em\u003e. The Kistler-9129AA was installed on the machining platform of the machining center through a special fixture. The fixture was mounted on the upper part of the dynamometer via a bolt, and the acoustic emission sensor was affixed to one side of the fixture through a magnetic pressure head.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAccording to the analysis results of the scale-span FE model and experimental results which are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a), the entire drilling process can be divided into four phases according to the interaction effects between twist drill bit and BCF/PEEK. In phase 1: the tool tip progressively penetrates the material, increasing the contact area between the tool face and the workpiece. Simultaneously, both thrust force and temperature steadily escalate. In phase 2: With the tool tip fully immersed in the material, the primary cutting edge actively cuts within the workpiece. Consequently, the material's stiffness starts to diminish, causing the rate of thrust force increase to slow down. Despite this deceleration, both thrust force and temperature continue to rise gradually, peaking in this phase. In phase 3: the tool tip has penetrated through the material, and the primary cutting edge is reaming within the workpiece. As the material's stiffness decreases further, thrust force experiences a rapid decline, while temperature gradually decreases. In phase 4: the primary cutting edge emerges from the workpiece surface. The decline in thrust force stabilizes, while temperature continues to decrease. With the tool completely withdrawn from the workpiece, the drilling process concludes once the tool bit is lifted. Under such a large thrust force, the phenomenon of debonding and delamination between laminates was prone to occur. From the cross-section of BCF/PEEK, it could be seen that under a large thrust force, there was obvious delamination damage between each layer, and the quality of hole making was particularly poor, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe various process parameters of the drilling experiment were also selected in accordance with the settings of the above scale-span FE analysis, namely, the spindle rotation speed was set to \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;5000r/min, and the feed speed was set to \u003cem\u003ef\u003c/em\u003e\u0026thinsp;=\u0026thinsp;120mm/min. Following all drilling experiments, the morphology of the hole outlet and hole wall was observed using the INSIZE ISM-PM600SB digital microscope and DSX series microscope, respectively. Prior to observing the morphology of the hole wall, the hole was cut using a cutting machine, and half of the hole wall with better integrity was selected for observation, which is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. These corresponding experimental results observed that the hole-making quality of the traditional twist drill was poor, with large areas of tearing and patches of burr, serious delamination, low cylindricity of the hole, poor edge uniformity at the exit, and large hole wall roughness.\u003c/p\u003e \u003cp\u003eBased on the above research and analysis, the defects of twist drills in the drilling of BCF/PEEK were as follows: the thrust force in the drilling process was too large due to the thrust effect of the transverse edge, and the extrusion effect of the cutting edge on the material exceeded its shear effect, resulting in obvious delamination between the laminates. The process parameters suitable for the drilling of BCF/PEEK were selected through a combined analysis method involving scale-span FE simulation and experimentation. However, it was observed that the drilling quality of traditional twist drills was poor in all results. Therefore, for achieving high-quality drilling of BCF/PEEK, it is necessary not only to select the appropriate process parameters but also to design a tool with a new bit structure and analyze its drilling characteristics.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Experiment of drilling holes with different novel tool","content":"\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Drilling tool design and experimental scheme\u003c/h2\u003e \u003cp\u003eIn response to the issue of poor hole quality in composite drilling caused by conventional twist drills, it is deemed necessary to design new tools for composite drilling. Due to the significantly lower bonding strength of the composite matrix resin compared to the tensile strength of the fibers, the interlaminar shear and tensile strength of the composite are considerably low. The transverse cutting action of the conventional twist drill is minimal, primarily involving the rolling and crushing of fibers, which, however, constitutes the primary source of thrust force [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eTherefore, considering the research presented in the previous chapter and the findings of previous studies, the longer transverse cutting structure of the traditional twist drill should be abandoned in the design of the new tools. This is done to enhance the shear capability of the fibers and reduce the generation of thrust drilling force, thereby improving hole quality. Following this principle, three novel drilling tools were designed: the dagger drill, the three-point twist drill and the three-point drilling and milling cutter, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e (a), (b) and (c). To investigate the performance of various new tools in drilling BCF/PEEK, drilling experiments were conducted on BCF/PEEK specimen plates. The diameters of the three new cutting tools were all 6mm.\u003c/p\u003e \u003cp\u003eAmong them, two three-point drills were designed by significantly reducing the transverse cutting length compared to the traditional twist drill, until it was transformed into a single cutting edge. This design allowed for a substantial reduction in the generation of thrust force. In addition to the primary cutting edge playing a role in cutting, an auxiliary cutting edge was also involved in the cutting process of the three-point twist drill, thereby enhancing its shear capability on fibers and reducing the occurrence of machining defects. The structure is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(a). The head of the three-point drilling and milling cutter featured a W-shaped structure with three points, and the sharp cutting tips on both sides could easily sever the fiber bundles of the composite, as depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e(b).\u003c/p\u003e \u003cp\u003eThe dagger drill, in contrast, was devoid of chip flutes, aiming to further minimize thrust forces. The corresponding drill head was essentially a combined drilling and reaming tool, with the point portion divided into the first cutting edge and the second cutting edge. During the drilling process, four peripheral cutting edges were directly involved in cutting, showcasing strong cutting capabilities. Hence, high-quality holes could be drilled. The main parameters of the dagger drill structure are presented in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe main structural parameters of the dagger drilling structure\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e(mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003eh\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e(mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003eα\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ed\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e(mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eh\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e(mm)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003eβ\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e118\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e50\u0026deg;\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eIn order to investigate the pre-drilled hole\u0026rsquo;s quality indicators such as forces and exit quality under various drilling parameters for different tool structures, an orthogonal experimental approach was employed in this study. For each type of tool, a double-factor, four-level orthogonal experiment was designed, with factor levels as presented in Table\u0026nbsp;\u003cspan refid=\"Tab4\" class=\"InternalRef\"\u003e4\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab4\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 4\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eOrthogonal experimental scheme\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"6\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNumber\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e/(r/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ef\u003c/em\u003e/(mm/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNumber\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e/(r/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ef\u003c/em\u003e/(mm/min)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe borehole arrangement of the specimen plate was as follows: approximately 10mm of space was left on both sides of the specimen plate in the longitudinal direction for clamping by the fixture. Subsequently, perforated holes were drilled on the specimen plate with different process parameters using a numerical control machining program. The center positions of every two holes were spaced 15mm apart. Each plate could accommodate 4\u0026times;5\u0026thinsp;=\u0026thinsp;20 holes, with one row designated as a reserve drilling area for holes where the drilling effect was suboptimal or data had not been collected, as illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e. During each drilling operation, the thrust force was monitored in real time, and images of the hole exit morphology were captured using a microscope. This was done to facilitate a comparative analysis of the drilling characteristics of different novel cutting tools in BCF/PEEK.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Analysis and discussion of experimental results\u003c/h2\u003e \u003cp\u003e(1) Macro evaluation of drilling damage\u003c/p\u003e \u003cp\u003eFor the holes obtained through drilling operations, the exit quality of the bore was observed using the INSIZE ISM-PM600SB digital microscope, and photographs of the exit morphology were taken for documentation. Varying degrees of damage were observed in the holes drilled by the three different types of tools, as inferred from the exit morphology of the holes. The exit morphology of the holes drilled by the three types of tools is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e. Taking as an example the holes produced by drilling with process parameters of spindle rotation speed at 2000 r/min and feed rate at 30 mm/min, a comparative analysis of the bore quality for each tool was conducted. The exit morphology of the holes drilled by the dagger drill is illustrated in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a). Fine fibrous burrs distributed at the exit of the hole could be observed. The overall neatness of the hole exit contour was relatively high, and its cylindricity was the highest among the holes drilled by the three types of tools. Comparatively, the best quality of pre-drilled hole is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e (b). Additionally, there were no apparent layering phenomena, indicating the optimal quality of bore production.\u003c/p\u003e \u003cp\u003eThe exit morphology of the holes processed by the three-point twist drill is depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b). In the extremely small edge region of the hole, there was minimal occurrence of short fibrous burrs, with the fibrous burrs being the least distributed among the three types of drill bits. The cylindricity of the hole was relatively high; however, there were evident manifestations of tearing and layering. The holes drilled by the three-point drilling and milling cutter, relatively speaking, did not exhibit excessive burrs and tearing. Overall, the cylindricity of the holes was not particularly high, showing a better statue than Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(a), while a worth one than Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(b). However, noticeable layering phenomena were observed, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e(c).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e(2) Analysis of maximum mean thrust force\u003c/p\u003e \u003cp\u003eSince thrust force is a crucial factor leading to defects at the hole exit, the maximum thrust force measured during the drilling process under various parameters is selected for analysis when comparing the drilling forces of different tool structures. This measurement is used as an assessment of the drilling performance of each tool.\u003c/p\u003e \u003cp\u003eThe three plots depicting the maximum thrust force are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e during the drilling process with the new tools under various process parameters. A strong correlation between process parameters and thrust force by the dagger drill was observed, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e(a). The maximum thrust force strictly decreased with the increase in spindle rotation speed and strictly increased with the augmentation of feed rate. The general variation trend of the thrust force of the three-point twist drill and the three-point drilling and milling cutter with the process parameters was similar to that of the dagger drill, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e(b) and Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e(c). Slightly different from the dagger drill, little change was observed in the thrust force of the three-point twist drill when the feed speed was 40mm/min, irrespective of the spindle rotation speed. Similarly, for the three-point drilling and milling cutter, little variation in the maximum thrust force was noted within the larger spindle rotation range when the feed speed was 50 or 60mm/min.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAbove all, the overall variation trend of the thrust force for the three-point twist drill and the three-point drilling and milling cutter was similarly to that of the dagger drill with respect to process parameters, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e(c). Slight deviations from the dagger drill were observed, wherein, for the three-point twist drill, minimal variations in thrust force occurred with changes in spindle rotation speed at a feed rate of 40 mm/min. Similarly, for the three-point milling cutter, at feed rates of 50 and 60 mm/min, within larger spindle rotation speed ranges, the maximum thrust force exhibited minimal changes.\u003c/p\u003e \u003cp\u003e(3) Measurement of damage factors of synthetic pre-drilled hole\u003c/p\u003e \u003cp\u003eFor a comprehensive and rational quantification of various hole exit damages on BCF/PEEK specimens after drilling, and further analysis of the perforation quality of different tools under various process parameters, a pre-drilled hole\u0026rsquo;s damage comprehensive evaluation method proposed by Liu et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e] was adopted in this study. Based on the structure of BCF/PEEK, a comprehensive assessment of perforation damage was conducted, with consideration given to burr formation, tearing, and delamination as three aspects for evaluation.\u003c/p\u003e \u003cp\u003eRegarding burr damage, minor burrs with lengths less than 0.2mm are initially disregarded, as their impact on the actual assembly quality of the hole is relatively insignificant. For longer burrs with lengths exceeding 0.2mm, different evaluation criteria are applied based on the width of the burr. When the burr width is less than 0.1mm, its length is utilized for characterization, whereas for burrs with widths greater than 0.1mm, characterization is performed using the area method. The burr damage coefficient \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003eb\u003c/em\u003e\u003c/sub\u003e is defined as.\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$${D}_{b}=\\alpha \\frac{2\\sum _{i=1}^{n}{L}_{i}}{d}+\\beta \\frac{4\\sum _{j=1}^{m}{A}_{j}}{\\pi {d}^{2}}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(1)\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\sum _{i=1}^{n}{L}_{i}\\)\u003c/span\u003e\u003c/span\u003e represents the length and sum of fine burrs that are not cut off around the hole. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\sum _{j=1}^{m}{A}_{j}\\)\u003c/span\u003e\u003c/span\u003erepresents the sum of the total area of the wide burr; \u003cem\u003ed\u003c/em\u003e stands the diameter of the hole; \u003cem\u003eα\u003c/em\u003e and \u003cem\u003eβ\u003c/em\u003e represent the weight factors of fine burrs and wide burrs affecting the quality of the hole, respectively. \u003cem\u003eα\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.2, \u003cem\u003eβ\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.8 are adopted in this study.\u003c/p\u003e \u003cp\u003eRegarding tearing damage, it is primarily defined as damage with a certain width and is commonly characterized using area parameters. The characterization principle involves the establishment of a criterion where the tearing length should not exceed three times the hole diameter, and the width should be less than 1.8mm. The tear damage coefficient \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003et\u003c/em\u003e\u003c/sub\u003e is defined as.\u003cdiv id=\"Equb\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equb\" name=\"EquationSource\"\u003e\n$${D}_{t}=\\frac{\\sum _{k=1}^{l}{A}_{k}}{4.8d}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(2)\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\sum _{k=1}^{l}{A}_{k}\\)\u003c/span\u003e\u003c/span\u003erepresents the cumulative area of small part of the tear, \u003cem\u003ek\u003c/em\u003e\u0026thinsp;=\u0026thinsp;2 is adopted in this study.\u003c/p\u003e \u003cp\u003eFor exit delamination damage, the evaluation metric involves measuring the area of the delamination region, and the lamination damage coefficient \u003cem\u003eD\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e at the exit is defined as.\u003cdiv id=\"Equc\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equc\" name=\"EquationSource\"\u003e\n$${D}_{d}=\\frac{4{A}_{d}}{\\pi {d}^{2}}-1$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(3)\u003c/p\u003e \u003cp\u003ewhere, \u003cem\u003eA\u003c/em\u003e\u003csub\u003e\u003cem\u003ed\u003c/em\u003e\u003c/sub\u003e represents the total area of the delamination zone.\u003c/p\u003e \u003cp\u003eWhen evaluating individual forms of damage, the reflection of bore quality remains unidimensional, resulting in significant randomness in the analysis results. Therefore, the composite influence of diverse damages on bore quality needs to be considered. Weighting factors are consequently assigned to the respective damage coefficients, leading to the derivation of a comprehensive damage factor denoted as \u003cem\u003eD\u003c/em\u003e, expressed as follows.\u003cdiv id=\"Equd\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equd\" name=\"EquationSource\"\u003e\n$$D={w}_{1}\\left(\\alpha \\frac{2\\sum _{i=1}^{n}{L}_{i}}{d}+\\beta \\frac{4\\sum _{j=1}^{m}{A}_{j}}{\\pi {d}^{2}}\\right)+{w}_{2}\\left(\\frac{\\sum _{k=1}^{l}{A}_{k}}{4.8d}\\right)+{w}_{3}\\left(\\frac{4{A}_{d}}{\\pi {d}^{2}}-1\\right)$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(4)\u003c/p\u003e \u003cp\u003ewhere, \u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e respectively represent the weight factors of burr, tear and delamination damage on drilled hole quality. According to the study on the change rule of damage coefficient caused by tool wear in the drilling process of Wen et al. [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], the values of \u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003ew\u003c/em\u003e\u003csub\u003e\u003cem\u003e3\u003c/em\u003e\u003c/sub\u003e are 1, 1.5 and 4 in this study, respectively.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eTo further analyze the drilling characteristics of various drill bit structures and identify the tool structure that exhibited optimal performance in controlling delamination damage, a lateral comparison of the comprehensive borehole damage factors for different drill bit structures was conducted under multiple process parameters, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig10\" class=\"InternalRef\"\u003e10\u003c/span\u003e. The comprehensive borehole damage factors were compared, and it was observed that the dagger drill exhibited the lowest borehole damage factors across all process parameters, as depicted in the four plots. The borehole damage factors for the dagger drill were consistently found to be at least 15% lower compared to the other two drill bit structures. The most significant disparity was observed at \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;5000r/min, \u003cem\u003ef\u003c/em\u003e\u0026thinsp;=\u0026thinsp;30mm/min, where the borehole damage factor for the dagger drill was 51.3% lower than that of the twist drill. Furthermore, minimal fluctuation in the borehole damage factor of the dagger drill was observed with variations in process parameters.\u003c/p\u003e \u003cp\u003eThe outstanding performance displayed by the dagger drill in ensuring bore quality was consistently maintained within 1.14 across all machining parameters. The borehole damage factor of the three-point drill-milling cutter was generally ranked just below that of the dagger drill, but the difference was substantial, ranging from 1.25 to 1.43. Considerable fluctuations in the damage factor were observed with variations in process parameters. For the three-point drill-milling cutter, after considering machining quality, the optimal processing parameters were determined to be \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;4000r/min, \u003cem\u003ef\u003c/em\u003e\u0026thinsp;=\u0026thinsp;30mm/min, resulting in a corresponding damage factor of 1.252. On the other hand, the borehole damage factor of the three-point twist drill was generally the highest across all parameters, with the maximum reaching up to 1.648. The borehole quality was the poorest, and it was significantly influenced by variations in spindle rotation speed. Therefore, the three-point twist drill was deemed unsuitable for precision machining of BCF/PEEK. According to the analysis of hole exit morphology, the best borehole quality was achieved with the dagger drill, followed by the three-point drilling bit and milling cutter, while relatively poorer borehole quality was exhibited by the three-point twist drill.\u003c/p\u003e \u003c/div\u003e"},{"header":"4. Drilling damage prediction considering process parameters using tapered drill-reamer","content":"\u003cp\u003eFrom the experimental research and analysis in section \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e3\u003c/span\u003e, it can be concluded that there is a strong correlation between thrust force and process parameters. Furthermore, delamination damage at the borehole exit is primarily caused by thrust force. Therefore, in order to predict borehole quality under specific process parameters, it is crucial to investigate the relationship between the damage factor and process parameters. Consequently, the derived relationship enables a quantitative prediction of the damage factor.\u003c/p\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Defect analysis based on damage factors\u003c/h2\u003e \u003cp\u003eThe regression analysis method is employed to ascertain whether a correlation exists between two or more sets of data by utilizing statistical principles. In this manner, the relationship between the dependent and independent variables is determined, and variations in the dependent variable can be predicted under different conditions of independent variables using this method. Since the reason that delamination damage is primarily caused by thrust force, delamination phenomena are likely to occur when a certain threshold of thrust force is reached. The relationship between damage factors and thrust force can be investigated through the application of regression analysis. Consequently, the regression equation for this relationship can be derived, enabling the prediction of the delamination extent for other parameters.\u003c/p\u003e \u003cp\u003eThe focus of this section is on the dagger drill, which is considered the optimal drilling tool for achieving high-quality holes among the three tools examined. A quantitative analysis of composite drilling damage was conducted, and the drilling damage factors of the dagger drill for various process parameters are presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab5\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 5\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe damage factors of the dagger drill\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"10\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c9\" colnum=\"9\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c10\" colnum=\"10\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eNum.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e/\u003c/p\u003e \u003cp\u003e(r/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ef\u003c/em\u003e/\u003c/p\u003e \u003cp\u003e(mm/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e/(N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003eNum.\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003en\u003c/em\u003e/\u003c/p\u003e \u003cp\u003e(r/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cem\u003ef\u003c/em\u003e/\u003c/p\u003e \u003cp\u003e(mm/min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c9\"\u003e \u003cp\u003e\u003cem\u003eF\u003c/em\u003e/(N)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c10\"\u003e \u003cp\u003e\u003cem\u003eD\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e128\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.087\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e101.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.105\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e143.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.134\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e109.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.138\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e161.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.130\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e11\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e119.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.118\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e171\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.084\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e4000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e138.7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.079\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e110\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.058\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e13\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e30\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.089\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e127.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.087\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e40\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e105.9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.107\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e138\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.116\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e15\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e50\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e115.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.090\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e3000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e147.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.076\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e5000\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c8\"\u003e \u003cp\u003e60\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c9\"\u003e \u003cp\u003e134.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c10\"\u003e \u003cp\u003e1.132\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eAfter qualitatively comparing the data presented in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, it was observed that the overall trend indicates an increase in the damage factor with the escalation of thrust force. However, a deviation from this general trend was noted in the tenth set of data, where the maximum damage factor among all holes was obtained under relatively low thrust force conditions. This deviation, contrary to the overall trend, lacked analytical value. The underlying reason for this anomaly may be attributed to the uneven thickness of the BCF/PEEK specimen during the preparation process, resulting in insufficient bonding strength between layers in certain regions. Consequently, severe delamination phenomena were more prone to occur during the drilling process in these areas. After excluding the tenth set of data, the remaining fifteen sets of data were imported into MATLAB software in the form of scatter plots. By conducting fitting, a regression equation between the damage factor and the maximum thrust force was derived. The fitted function is graphically represented in Fig.\u0026nbsp;\u003cspan refid=\"Fig11\" class=\"InternalRef\"\u003e11\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAccording to the graph of the fitted function, it could be distinctly observed that a robust relationship existed between the maximum thrust force and the damage factor, and the thrust force was amplified with the damage factor increasing. The equation derived from the fitting process can be written as.\u003cdiv id=\"Eque\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Eque\" name=\"EquationSource\"\u003e\n$${F}_{d}\\text{= 471000-34500}F\\text{+1115}{F}^{2}\\text{-21}{F}^{3}\\text{+0.25}{F}^{4}\\text{-0.002}{F}^{5}\\text{+}{F}^{6}*{10}^{-5}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(5)\u003c/p\u003e \u003cp\u003ewhere, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({F}_{d}\\)\u003c/span\u003e\u003c/span\u003e is damage factor. \u003cem\u003eF\u003c/em\u003e is maximum thrust force.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Multiple regression model of process parameters and thrust force\u003c/h2\u003e \u003cp\u003eThrough the analysis of the data from the aforementioned experiments in section \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e3\u003c/span\u003e, it was evident that a strong correlation exists between the thrust force of the dagger drill and the feed rate or spindle rotation speed. To quantitatively analyze the relationship between thrust force and process parameters, a multiple regression model was established, with the feed rate (\u003cem\u003ef\u003c/em\u003e) and spindle rotation speed (\u003cem\u003en\u003c/em\u003e) as independent variables, and the maximum thrust force (\u003cem\u003eF\u003c/em\u003e) as the dependent variable. The model equation formulated can be written as.\u003cdiv id=\"Equf\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equf\" name=\"EquationSource\"\u003e\n$$F=C{n}^{i}{f}^{j}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(6)\u003c/p\u003e \u003cp\u003ewhere, \u003cem\u003eC, i\u003c/em\u003e and \u003cem\u003ej\u003c/em\u003e denote constants.\u003c/p\u003e \u003cp\u003eFor ease of solution, taking the logarithm of both sides of Eq.\u0026nbsp;(5) results in Eq.\u0026nbsp;(6), thereby transforming the nonlinear problem into a linear problem for analysis.\u003cdiv id=\"Equg\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equg\" name=\"EquationSource\"\u003e\n$$InF=InC+iInn+jInf$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(7)\u003c/p\u003e \u003cp\u003eDuring the actual solving process, the first fifteen sets of data from Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e were imported into MATLAB software for fitting and calculating the model. The sixteenth set of data was reserved for validating the effectiveness of the model. The fitting equation was obtained as.\u003cdiv id=\"Equh\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equh\" name=\"EquationSource\"\u003e\n$$InF=6.11156-0.36075Inn+0.43508Inf$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(8)\u003c/p\u003e \u003cp\u003eThree parameters were calculated as follows: \u003cem\u003eC\u003c/em\u003e\u0026thinsp;=\u0026thinsp;451, \u003cem\u003ei\u003c/em\u003e=-0.36075, \u003cem\u003ej\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.43508. The regression equation of the maximum thrust force was obtained by substituting the obtained parameter values back into Eq.\u0026nbsp;(5).\u003cdiv id=\"Equi\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equi\" name=\"EquationSource\"\u003e\n$$F=451{n}^{-0.36075}{f}^{0.43508}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(9)\u003c/p\u003e \u003cp\u003ewhere, the unit of \u003cem\u003eF\u003c/em\u003e is \u003cem\u003eN\u003c/em\u003e, the unit of \u003cem\u003en\u003c/em\u003e is r/min, and the unit of \u003cem\u003ef\u003c/em\u003e is mm/min.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab6\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 6\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eSummary of fitting statistics\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c2\" namest=\"c1\"\u003e \u003cp\u003e\u003cem\u003eIn C\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c4\" namest=\"c3\"\u003e \u003cp\u003e\u003cem\u003ei\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"2\" nameend=\"c6\" namest=\"c5\"\u003e \u003cp\u003e\u003cem\u003ej\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eStatistics\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eStandard error\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eStandard error\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003eValue\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003eStandard error\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAdjusted \u003cem\u003eR\u003c/em\u003e\u003csup\u003e2\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e6.11156\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e0.16225\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e-0.36075\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.0163\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e \u003cp\u003e0.43508\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e0.02165\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003e0.98622\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab7\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 7\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eThe thrust force regression model test\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026times;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eModel\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDOF\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eSquares\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eSquare-mean\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eValue of \u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003esignificance level\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eProbability\u0026gt;\u003cem\u003eF\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRegression\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.44715\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.22357\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e502.0307\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.05\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026times;\" colname=\"c7\"\u003e \u003cp\u003e2.713\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;12\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eResidual\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.00534\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e4.453\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;4\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSum\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e14\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.45249\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe summary of the relevant statistical values of the regression obtained by fitting is shown in Table\u0026nbsp;\u003cspan refid=\"Tab6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. When taking the significance level \u003cem\u003eα\u003c/em\u003e\u0026thinsp;=\u0026thinsp;0.05, the calculated R\u003csup\u003e2\u003c/sup\u003e was 0.98622. The thrust force regression model test is presented in Table\u0026nbsp;\u003cspan refid=\"Tab7\" class=\"InternalRef\"\u003e7\u003c/span\u003e, where \u003cem\u003eF\u003c/em\u003e\u0026thinsp;=\u0026thinsp;502.0307, and the probability greater than \u003cem\u003eF\u003c/em\u003e was only 2.713\u0026times;10\u003csup\u003e\u0026minus;\u0026thinsp;12\u003c/sup\u003e, indicating a better fitting effect. Substituting spindle rotation speed \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;5000r/min and feed speed \u003cem\u003ef\u003c/em\u003e\u0026thinsp;=\u0026thinsp;60mm/min from the 16th set of data in Table\u0026nbsp;\u003cspan refid=\"Tab5\" class=\"InternalRef\"\u003e5\u003c/span\u003e into the regression equation formula, a calculated predicted value of \u003cem\u003eF\u003c/em\u003e\u0026thinsp;=\u0026thinsp;124\u003cem\u003eN\u003c/em\u003e was obtained. Comparing this value with the real measured value of 134.5\u003cem\u003eN\u003c/em\u003e, the error was only 8.5%, indicating that the regression model could predict the maximum thrust force in the drilling process with two-factor variation more accurately.\u003c/p\u003e \u003cp\u003eFrom the expression of the regression equation, it also could be observed that the spindle rotation speed and feed rate interact to influence the maximum thrust force. By increasing the spindle rotation speed and decreasing the feed rate, the thrust force can be effectively reduced.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Prediction and verification of drilling damage under different parameters\u003c/h2\u003e \u003cp\u003ePreviously, the fitting Eq.\u0026nbsp;(4) for the relationship between the damage factor and the maximum thrust force was obtained through a univariate regression. In this chapter, the fitting Eq.\u0026nbsp;(9) expressing the relationship between the maximum thrust force, spindle rotation speed, and feed rate was derived using bivariate regression. The relationship between the damage factor \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({F}_{d}\\)\u003c/span\u003e\u003c/span\u003e and the two process parameters was obtained by substituting Eq.\u0026nbsp;(9) with Eq.\u0026nbsp;(4).\u003cdiv id=\"Equj\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equj\" name=\"EquationSource\"\u003e\n$${F}_{d}\\text{= 471000-34500}*\\left(451{n}^{-0.36075}{f}^{0.43508}\\right)\\text{+1115}{F*\\left(451{n}^{-0.36075}{f}^{0.43508}\\right)}^{2}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equk\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equk\" name=\"EquationSource\"\u003e\n$$\\text{-21}{*\\left(451{n}^{-0.36075}{f}^{0.43508}\\right)}^{3}\\text{+0.25}{\\left(451{n}^{-0.36075}{f}^{0.43508}\\right)}^{4}$$\u003c/div\u003e\u003c/div\u003e\u003cdiv id=\"Equl\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equl\" name=\"EquationSource\"\u003e\n$$\\text{-0.002}{451{n}^{-0.36075}{f}^{0.43508}}^{5}\\text{+}{451{n}^{-0.36075}{f}^{0.43508}}^{6}*{10}^{-5}$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e \u003cp\u003e(10)\u003c/p\u003e \u003cp\u003eThe relationship and impact patterns between spindle rotation speed, feed rate, and damage factor during the drilling process with dagger drills were explicitly articulated in Eq.\u0026nbsp;(10). It could be quantitatively observed from the formula that the layering degree of the hole outlet can be effectively reduced, and the quality of the hole can be improved by selecting perforating process parameters with spindle rotation speed and low feed rate. On one hand, the relationship between the damage factor and the process parameters can be utilized to predict the damage factor of the hole drilled under known process parameters and characterize the quality of hole formation. On the other hand, suitable process parameters for the drilling process can be chosen to attain a specific quality, which holds significant practical value and significance.\u003c/p\u003e \u003cp\u003eTo assess the predictive capability of the model for the comprehensive damage factor, two additional sets of process parameters were selected and substituted into Eq.\u0026nbsp;(9). The model's predicted damage factor values were then computed. Subsequently, drilling experiments were conducted under these two sets of process parameters, and the actual damage factor values were observed and calculated. A comparative analysis was then undertaken between the predicted and experimental values to analyze the prediction errors. Two groups of extreme and exceptional process parameters are as follows: (1) Spindle rotation speed \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1000r/min, feed speed \u003cem\u003ef\u003c/em\u003e\u0026thinsp;=\u0026thinsp;70mm/min; (2) Spindle rotation speed \u003cem\u003en\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6000r/min, feed speed \u003cem\u003ef\u003c/em\u003e\u0026thinsp;=\u0026thinsp;20mm/min. Three holes were drilled under each group of process parameters, and the average value of the damage factors for the three holes was taken as the actual damage factors under the group of process parameters.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig12\" class=\"InternalRef\"\u003e12\u003c/span\u003e presents the data of experimental damage factors and predicted damage factors, while it is also depicted the comparative analysis chart of drawing errors. From the experimental results, it could be observed from the chart that the real damage factor value of experiment, conducted with low feed rate and high spindle rotation speed, was slightly larger than the predicted value calculated by Eq.\u0026nbsp;(10), with an error of 0.276%. Conversely, under the condition of high spindle rotation speed and low speed rate, the actual damage factor value is slightly smaller than the predicted value, with a margin of error of 0.444%. These results indicate that the established model can accurately predict the comprehensive damage factors of dagger drilling outlets, highlighting its valuable application potential.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis paper presents a novel method for selecting optimal drilling tools and damage prediction analysis in BCF/PEEK drilling. Firstly, a comprehensive analysis is conducted on the reasons behind drilling damage defects caused by traditional twist drills using a scale-span FE model based on modified micromechanics of failure criterion with new damage evolution laws. Subsequently, the causes of damage defects in prefabricated holes resulting from twist drills are investigated through simulation results, and the accuracy of the simulation model is validated through corresponding experiments. Following this, three innovative types of drilling tools are designed, and orthogonal experiments on BCF/PEEK drilling are conducted. Data on hole exit morphology, thrust force, and damage factors are systematically collected and observed, enabling a comprehensive comparative analysis of the drilling performance of each tool. Lastly, a process parameters-oriented drilling damage prediction method is introduced. Regression models for damage factor and thrust forces, as well as thrust force and process parameters, are respectively established, with thrust force serving as the intermediate variable. The regression equations are derived through fitting and solving, elucidating the relationship between damage factor and process parameters. Based on the above research, the following conclusions can be drawn.\u003c/p\u003e \u003cp\u003e(1) The preliminary experimental findings demonstrate that the scale-span FE drilling model can accurately simulate various defects during BCF/PEEK drilling. The analysis reveals that the maximum thrust force can still exceed 400N. Drilling experiments with a traditional twist drill under identical process parameters indicate the presence of numerous burrs and delamination damage at the hole outlet, resulting in suboptimal hole quality.\u003c/p\u003e \u003cp\u003e(2) The thrust force during drilling with the dagger drill is consistently more than one-third smaller than that of the two three-point drills, leading to minimal damage at the hole exit. Regardless of process parameters, the hole exit damage factor remains below 1.14, significantly outperforming the two three-point drills and ensuring superior hole quality.\u003c/p\u003e \u003cp\u003e(3) Multiple nonlinear regression analyses are conducted to establish an equation describing the relationship between thrust force, spindle speed, and feed rate. At a significance level of α\u0026thinsp;=\u0026thinsp;0.05, the coefficient of determination is found to be 0.98622, indicating a high degree of goodness of fit. This analytical approach not only establishes the correlation between the damage factor and process parameters but also validates the model's robustness in capturing the intricate relationships within the machining process.\u003c/p\u003e \u003cp\u003e(4) The maximum error is 0.276% at high spindle rotation speed and low feed rate, and 0.444% at high feed rate and low spindle rotation speed, affirming the accuracy of the method. Using thrust force as an intermediary parameter, a regression equation describing the relationship between thrust force and the damage factor is derived through simple nonlinear regression.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to acknowledge the editors and the anonymous referees for their insightful comments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis article does not contain any studies with human participants performed by any of the authors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWork was conducted with no human test subjects.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWork has consent to publish.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors\u0026rsquo; contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eYong Liu\u0026nbsp;\u003c/strong\u003edesigned the study, performed the research, analysis data, and wrote the paper. \u003cstrong\u003eShenao Zhu and Guangyao Xu\u003c/strong\u003e conducted experiments and data processing. \u003cstrong\u003eMeng Zhu\u003c/strong\u003e provided simulation experimental data and designed the drilling tool bit. \u003cstrong\u003eZitao Pan\u003c/strong\u003e modified the paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe work reported herein is sponsored by the National Natural Science Foundation of China (52105450), the University Science Research Project of Jiangsu Province (No. 21KJB460016). The authors would like to acknowledge the editors and the anonymous referees for their insightful comments.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAuthors declare that they have no competing interests.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe experimental and simulation data is transparency.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZeng J J, Yan T Z, Jiang Y Y, et al. 3D printing of FRP grid and bar reinforcement for reinforced concrete plates: Development and effectiveness. Composite Structures, 2024, 335 117946.\u003c/li\u003e\n\u003cli\u003eXing L, Jian F W, Heng C B, et al. Effect of groove configuration on mechanical properties and fracture behavior of 6061 Al alloy and CFRTP laser joint. 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Key Engineering Materials, 2011, 1371 (487): 371-375.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"BCF/PEEK, Scale-span drilling FE model, Drilling tools, Process parameters prediction","lastPublishedDoi":"10.21203/rs.3.rs-4480703/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4480703/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe effective design of tool geometry and optimization of process parameters play a pivotal role in mitigating damages such as tearing, burrs, and delamination during the drilling process of braided carbon fiber reinforced poly ether ether ketone (BCF/PEEK). This study introduces a novel method for selecting optimal drilling tools and damage prediction analysis in BCF/PEEK drilling. Firstly, a scale-span drilling finite element (FE) model is established based on the analysis of twist bit geometry and BCF/PEEK composition. Simulation and experimental validation identify damage causes in prefabricated holes. Subsequently, three innovative types of designed drilling tools are evaluated based on factors like hole morphology, thrust force, and delamination. Finally, Regression models are established to correlate damage factors, thrust force, and process parameters. The research findings indicate that the use of twist drill bits results in higher thrust forces, leading to delamination defects at hole exits. Conversely, employing a tapered drill-reamer could enhance the exit quality of prefabricated holes, consistently maintaining damage factors below 1.14 under identical process parameters. The proposed method effectively predicts the exceptional process parameters, with a maximum error of only 0.276% in the drilling of BCF/PEEK.\u003c/p\u003e","manuscriptTitle":"A Novel Method for Damage Prediction in BCF/PEEK Drilling Using an Innovative Drill Tool","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-11 12:25:42","doi":"10.21203/rs.3.rs-4480703/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2024-08-27T05:39:58+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2024-05-31T07:37:02+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-05-29T12:59:00+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-29T07:26:02+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2024-05-26T11:52:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"the-international-journal-of-advanced-manufacturing-technology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jamt","sideBox":"Learn more about [The International Journal of Advanced Manufacturing Technology](https://www.springer.com/journal/170)","snPcode":"170","submissionUrl":"https://submission.nature.com/new-submission/170/3","title":"The International Journal of Advanced Manufacturing Technology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"fc67ae4a-ffec-4a9e-a00f-89fac45850aa","owner":[],"postedDate":"June 11th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-03-10T19:56:19+00:00","versionOfRecord":{"articleIdentity":"rs-4480703","link":"https://doi.org/10.1007/s00170-025-15303-6","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2025-03-05 15:57:44","publishedOnDateReadable":"March 5th, 2025"},"versionCreatedAt":"2024-06-11 12:25:42","video":"","vorDoi":"10.1007/s00170-025-15303-6","vorDoiUrl":"https://doi.org/10.1007/s00170-025-15303-6","workflowStages":[]},"version":"v1","identity":"rs-4480703","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4480703","identity":"rs-4480703","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}