Comparison between Cold Incremental and Stretch Forming of Flax Fiber-Reinforced Polypropylene Composites

Comparison between Cold Incremental and Stretch Forming of Flax Fiber-Reinforced Polypropylene Composites | 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 Comparison between Cold Incremental and Stretch Forming of Flax Fiber-Reinforced Polypropylene Composites Antonio Formisano, Dario De Fazio, Antonio Langella, Martina Panico, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6886441/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Dec, 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 Incremental sheet forming, born as a versatile and cost-effective alternative to traditional procedures to deform incrementally and without dedicated dies flat metal sheets into complex three-dimensional shapes, has recently been gaining attention as a forming technique for polymers and composites. Among these, natural fiber-reinforced thermoplastics have been climbing in popularity because natural fibers are widely available, act as effective polymer reinforcement, and make the composite semi-biodegradable. Through compression molding and using natural woven fabrics, it is also possible to achieve good fiber/matrix coupling without compromising the environmental benefits with chemical coupling agents and/or treatments. This experimental study compares cold incremental and stretch forming processes of flax woven fabric-reinforced polypropylene composites for the manufacture of spherical caps. By considering formability, geometrical accuracy, forming forces, power, and energy consumption, the study highlights the effectiveness of incremental forming applied to these biobased composites, without resorting to full counter dies and heating stages. Incremental Forming Stretch Forming Polypropylene Flax Geometrical Accuracy Forces Energy Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Introduction Incremental sheet forming (ISF) is a technique that, in its simplest variant, known as negative incremental forming (NIF), involves the incremental deformation of a clamped sheet through the progressive action of a simple and non-dedicated forming tool, driven by a CNC machine to obtain the desired final shape [ 1 ]. Its layered manufacturing strategy matches well with the production of customized and free-form parts [ 2 ], finding application in several industrial fields such as aerospace [ 3 ], automotive [ 4 , 5 ], and medical [ 6 , 7 ] applications, and so on. Many studies have been conducted to compare ISF with other conventional sheet forming processes. They have highlighted some unique ISF characteristics, such as reduced tooling, cost-effectiveness, short setup time, high formability and flexibility, low environmental impact, but also high process time and geometric inaccuracies due to the absence of counter dies [ 8 – 11 ]. ISF was originally conceived and subsequently developed for metal and metal alloy sheets, as evidenced by several works [ 12 – 15 ]. Recently, research on ISF has shown increased interest in non-metallic materials like thermoplastic polymers and composites. While ISF of thermoplastics, whose properties make them widely used for mass production [ 16 ], has been investigated in several studies [ 17 – 19 ], demonstrating its potential to replace the traditional processes based on repetitive heating, shaping, and cooling actions [ 20 , 21 ], research on the ISF of composite materials remains limited. Starting from preliminary works [ 22 , 23 ] and arriving at advances in ISF of polymer-based composites reinforced with glass [ 24 ] and carbon fibers [ 25 ], it is clear that ISF can represent a sustainable and cost-effective way for composite forming [ 26 ]. An area of significant interest in recent years, both in research and on an industrial scale, is the use of natural fibers (from seeds, stems or roots) as reinforcements for polymer composites [ 27 ]. These fibers represent a low-cost, biodegradable, renewable, and nontoxic alternative to the most common synthetic reinforcements (glass and carbon fibers) [ 28 ]. They enhance certain properties of commercial polymers, may contribute to lowering the energy demand during processing, and make them semi-biodegradable [ 29 ]. Hemp and flax are the strongest and stiffest natural fibers [ 30 ], as well as two of the most popular and widely available fibers in European countries. They are composed of a complex microstructure consisting of bundles of twisted elementary fibers that are glued together by an amorphous matrix of pectin, hemicelluloses, and lignin [ 31 , 32 ]. These fibers exhibit excellent vibration damping properties, as well as low density and high specific stiffness compared to glass or aramid fibers, and are commonly used for the manufacture of biocomposites [ 33 ]. Thermoplastics as composite matrices are used in many fields, such as automotive [ 34 ], aeronautics [ 35 ], and biomedical [ 36 ] applications; they show some significant advantages compared to thermosets, in terms of short process time, potential recyclability, and the possibility to be remodeled at high temperatures [ 37 , 38 ]. Polypropylene (PP) is the world's second-most widely produced synthetic polymer. Thanks to its high chemical and wear resistance, excellent mechanical properties, ease of processing, and cost-effectiveness [ 39 ], it finds application in automotive parts, reusable containers, packaging, and laboratory equipment [ 40 ], as well as for advanced composites in aerospace, civil, and automotive fields [ 41 ]. In addition, along with polyethylene and polyvinyl chloride, PP currently dominates as a matrix for natural composites [ 42 ]. The adhesion between the matrix and fibers plays an essential role in the stress transfer of composites. Poor adhesion in natural fiber-reinforced polymers can be improved by chemical fiber pretreatments; the most common are alkaline and silane treatments, but isocyanate, peroxide, acetylation and maleic treatments have also been analyzed [ 43 – 45 ]. Alternatively, another chemical solution involves adding a coupling agent to the matrix; the most common agent for natural fiber-reinforced PP composites is maleic anhydride-grafted polypropylene [ 46 ]. Together with chemical treatments, another viable way to improve the natural fibers/polymer matrix interaction is the use of reinforcements in the form of fabrics to generate a mechanical coupling. This solution, already considered for metal foams [ 47 ] and sandwich structures [ 48 ], can be considered for thermoplastics reinforced with natural fibers in the form of fabric by using the compression molding technique [ 49 ]; the main process parameters that influence the composite performance are the temperature, the dwelling time, and the molding pressure. This work presents an experimental campaign based on ISF and stretch forming (SF) tests, with and without a partial counter die, for the manufacture of spherical caps, starting from natural fiber-reinforced PP composites. The laminates were manufactured by compression molding using flax woven fabrics, but without fiber treatments or coupling agents; these further production steps would have increased the manufacturing process time and costs, as well as decreased the environmental benefits associated with the use of flax fibers. The forming processes were conducted without localized heating [ 50 ] and without using full counter dies to preserve the flexibility and ease of use of the ISF process. Despite not allowing for very high wall angles [ 51 ], this process can be used for applications such as shaping stiffening ribs for panels in the automotive, aviation, and naval fields [ 52 ]; consequently, a component like a spherical cap, with decreasing wall angle and deformation states, was chosen. Through the acquisition of the cap profiles and the evaluation of formability, forming forces, power, and energy consumption, the experimental campaign highlights the benefits and drawbacks of using ISF, compared to SF process, for these biobased composites. Materials and Methods This section describes the manufacturing process of the composite laminates, the forming of the spherical caps, and the features evaluated for comparing between the two forming procedures. Manufacture of the laminates The composite laminates used in this study (area of 200 × 150 mm 2 , thickness of 2.2 mm) were manufactured using neat PP films (supplied by GDC S.r.l.; thickness of 0.5 mm and density of 0.92 g/cm 3 ) and a woven fabric of flax, supplied by FIDIA S.r.l. - Technical Global Services. The fabric had a mass per unit area of 320 g/cm 2 , a tex number of 324 g/km, and was safely stored in a polymeric bag under vacuum at 20°C and 45% humidity. As previously mentioned, it was not subjected to any previous chemical or surface treatment. Before the molding process, it was dried at 60°C for 12 hours to eliminate any trace of humidity. A figure of the fabric and a magnification of a single yarn constituted by the winding of filaments are shown in [ 53 ], while their main properties are summarized in [ 51 ]. The laminates were produced using a conventional compression molding press, considering the stacking sequence (five layers with a symmetric layup; the first and the last two layers were PP films, while the central layer was flax fabric) and following the operations schematized in Fig. 1 . Specifically, the molding temperature was 200°C, and the total molding time was 300 s, with the first 120 s being the dwelling time, a waiting period after which the plates were closed, applying a pressure of 4 MPa for the remaining 180 s. The choice of a woven fabric with a large mesh size and the process parameters mentioned above proved to be an effective solution for the manufacture of flax and hemp fiber-reinforced PP composites, even with a different stacking sequence [ 53 ]. Compared to unreinforced PP, these composites showed notable improvements in tensile and bending properties, as well as higher bearing capacities and service temperatures. Forming tests Spherical caps (see the schematization in Fig. 2a, where a and θ denote the base radius and the polar angle, respectively) were manufactured using cold NIF and SF processes (see Fig. 2b and Fig. 3 for a schematization and the actual equipment of the tests); the forming tests were conducted using a C.B. Ferrari high-speed four-axis vertical machining center. The laminates were secured using a clamping frame with a square working area of 100 × 100 mm 2 . To reduce the sheet bending defect close to the base of the cap, the tests were also conducted using a hollow cylinder as a partial counter die; differently from a full counter die, it only supports the essential areas of the sheet, allowing to manufacture components with some similarities and preserving the process flexibility. Additionally, the probability of failures and defects was reduced by carrying out the tests under lubricated conditions, using Boelube 70104 (100A) synthetic lubricant, developed by Boeing and supplied by Orelube. The incremental and stretch forming tests without partial counter die are labelled as NIF 0 and SF 0 , respectively, while the corresponding ones with partial counter die as NIF PD and SF PD , respectively. Two tests for each different case were performed. For the NIF tests (see Fig. 3 a), a non-rotating stainless-steel stylus with a hemispherical head, 10 mm in diameter, was driven by the CNC machine at a nominal speed v NIF = 1000 mm/min to impose progressive deformation on the laminate. The tool followed a path with helical turns that alternated in anticlockwise and clockwise directions. This approach, based on observations for metal [ 12 ] and polycarbonate ISF parts [ 54 ], significantly reduced the probability of twisting, as the twist produced in one turn is almost completely recovered in the next [ 55 ]. Figure 4 shows a not-to-scale representation of some turns of the toolpath; θs = 1° is the angular step down, i.e., the angular distance described after one complete turn. For the SF tests (see Fig. 3 b), the machine simply imposed on the die a vertical displacement, equal to the cap height (equal to 18.65 mm), at a nominal speed v SF = 60 mm/min. Measured features To evaluate the geometrical accuracy of the processes, the shape of the caps was measured using a Zeiss DuraMax coordinate measuring machine (measurement accuracy of 2.4 µm) and Calypso software and then compared to the target geometry. A ruby sphere stylus with a diameter of 3.0 mm was used for the measurements. Each measurement involved 450 individual points evenly distributed across the diagonals AC and BD (see Fig. 2a). To estimate the magnitude of the forming loads, F X , F Y , and F Z forces were acquired at 50 Hz by the K-MCS10 multicomponent sensor (fixed between the clamping fixture and the base plate of the CNC machine, see Fig. 3 ), equipped with the QuantumX MX840B data acquisition system and the Catman Easy AP software. From their combination, the magnitudes of the force in the XY plane and of the total forming force (labelled as F XY and F TOT , respectively) were also obtained. The forces also enabled the measurement of power ( P ) and energy consumption ( E ). Unlike the evaluation of the electrical energy, the use of forces allows for the estimation of the actual energy required for the process, which represents only a small fraction of the total energy consumed, as most of the energy demand is associated with auxiliary functions of the equipment [ 56 ]. For the NIF tests, P was obtained by only considering the contribution of F XY , according to the following equation: P ≈ P XY = F XY ∙ v NIF (1) This simplification is possible because, for the NIF processes, v NIF can be approximated with the speed in the XY plane, due to the low θs value that makes the path almost horizontal, while the speed along the Z axis is very low and does not significantly contribute to the total power and energy. This was observed in a previous study by the authors on NIF of cones and spherical caps starting from laminates of flax and hemp fiber-reinforced PP composites [ 57 ]; the simplification resulted in an underestimation in terms of energy of less than 2.5% in the worst case. For the SF tests, P was determined by: P = F Z ∙ v SF (2) E trends were determined as time-integrals of the P curves. The Riemann integral was used, with a regular partition of the time interval equal to 0.02 s, i.e. the period of acquisition of the forces. Results and Discussion This section summarizes and discusses the main results of the experimental campaign. The first part addresses the feasibility and geometric accuracy of the processes, while the second part analyzes the forming forces, power, and energy. Given the limited variability observed among repetitions, only representative curves and average values of the investigated features are reported for the sake of conciseness. Feasibility and geometrical accuracy Spherical caps with a = 40 mm and θ = 50° were manufactured using NIF and SF processes, with and without a partial die (with internal and external diameters of 80 and 100 mm, respectively). In all cases, the parts were sound and had good surface quality; moreover, non-severe working conditions were achieved, as highlighted by the lack of instabilities and wrinkling [ 58 ]. An NIF PD cap is reported in Fig. 5 . Figure 6 shows the actual and the target cap shapes (for easy reading, only half of the experimental profiles are reported). Two features were evaluated to estimate the geometrical accuracy of the forming processes, i.e. the difference in maximum height ( dh 1 ) and the gap in correspondence of the intersection between the base of the cap and the flange ( dh 2 ); Table 1 summarizes these values. Table 1 dh 1 and dh 2 values for the geometrical accuracy of the forming processes. Feature Test NIF 0 NIF PD SF 0 SF PD dh 1 [mm] 3.4 2.8 13.5 12.8 dh 2 [mm] 3.6 2.2 1.9 2.6 The NIF process guaranteed a more accurate geometrical quality due to the incremental and localized nature of the deformation mechanism, and the use of the partial die improved it, particularly near the clamped zone; in contrast, the SF process proved to be completely ineffective, in both the variants. The stretching mechanism proved to be unsuitable for these geometries when starting from cold laminates, resulting primarily inelastic deformations that were almost entirely recovered after processing. The low formability efficiency of the SF processes was further confirmed by more severe forming tests to obtain spherical caps with a = 20 mm and θ = 70° (see Fig. 7). While the NIF tests were concluded without incurring failures (Fig. 7a), the SF tests failed, as highlighted in Fig. 7b. Forces, power, and energy Figure 8 reports the trends of F TOT . Concerning the NIF tests (Fig. 8a), the fluctuations of the trends reflected the alternating nature of the toolpath. The initial part of the NIF PD curve had a higher slope, due to the contact of the laminate with both the tool and the counter die, which made the system highly stiff. This resulted in reduced dh 1 and dh 2 values, as the flange acted as a weak constraint in NIF 0 , compared to the more effective action provided by the counter die in NIF PD . The curves reached their maximum value, corresponding to the condition of maximum tool/sheet contact, during which the processes exhibited their most effective incremental deformation of the laminates. The final part of the curves showed a decreasing trend, as a consequence of the less severe working conditions encountered when the tool reached the top of the caps, due to the decreasing wall angle. Figure 8b reports F TOT trends when using the SF processes. The forces continuously increased, because of the increasing contact area between the die and the laminate as the tool displacement increased. But they did not result effective in terms of formability, as observed by Fig. 6 . Figure 9 reports the power curves. They obviously followed the same trend of the forming forces, both for NIF (Fig. 9a) and SF tests (Fig. 9b), since they were obtained by multiplying them and constant values of velocity. Finally, Fig. 10 reports the energy curves. They showed an increasing trend, because they were obtained by integrating the power curves. Table 2 summarizes the results of this subsection, reporting the maximum values of F TOT , P and E . In all cases, higher values were recorded when using the partial counter die, because of a higher stiffness of the system. The low forming forces for NIF processes confirmed the above predicted non-severe working conditions and the usability of non-dedicated tools and machines. This was not true for SF processes, for which the higher values of forces reached did not guarantee forming efficiency. Both NIF and SF processes required low and similar power levels, while the energy for NIF processes, compared to SF, was higher due to the high process time but guaranteed a good formability. Table 2 Maximum values of F TOT , P and E Feature Test NIF 0 NIF PD SF 0 SF PD F TOT,MAX [N] 473 536 3621 6313 P MAX [W] 1.9 2.0 3.6 6.3 E MAX [J] 441.0 563.1 21.3 34.2 Conclusions This work compares the incremental and the stretch forming applied to laminates of flax woven fabric-reinforced polypropylene composites, obtained by compression molding and without fiber treatments or coupling agents; the processes for the manufacture of spherical caps were carried out at room temperature, without and with a partial counter die. From the comparison of the geometric profiles, the incremental forming process results effective for obtaining the designed components, especially when using the partial counter die, due to the incremental and localized approach that guarantees good deformation levels also under cold working conditions; on the other hand, stretch forming proves to be highly ineffective, while using the partial counter die, with the prevalence of the elastic response of the laminates. The forming force levels for the incremental forming are extremely limited and this translates into non-severe working conditions and reduced risks for the equipment, differently from what observed for the stretch forming. Both the processes require very low power; the higher but however limited energy levels for the incremental forming process reflect the high process time, one of the main cons of this technique. Future research could consider the evaluation of the mechanical properties of the components, and the feasibility of remolding panels after incremental forming. In addition, and according to a sustainable manufacturing perspective, it could be of interest to investigate the incremental forming of completely natural composite laminates. Declarations Declaration of generative AI and AI-assisted technologies in the writing process During the preparation of this work the author(s) used Copilot in order to improve its readability. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication. Funding The authors declare that no funds, grants, or other support were received during the preparation of this manuscript. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions All authors contributed to the study conception and design. 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Compos Part B Eng 184:107727. https://doi.org/10.1016/j.compositesb.2019.107727 Torres S, Ortega R, Acosta P, Calderón E (2021) Hot incremental forming of biocomposites developed from linen fibres and a thermoplastic matrix. Stroj Vestnik/Journal Mech Eng 67:123–132. https://doi.org/10.5545/sv-jme.2020.6936 Formisano A, Boccarusso L, De Fazio D, et al (2025) Considerations on the incremental forming of natural fibre-reinforced polypropylene composites. Mater Res Proc 54:2238–2245. https://doi.org/10.21741/9781644903599-241 Hariprasad K, Ravichandran K, Jayaseelan V, Muthuramalingam T (2020) Acoustic and mechanical characterisation of polypropylene composites reinforced by natural fibres for automotive applications. J Mater Res Technol 9:14029–14035. https://doi.org/10.1016/j.jmrt.2020.09.112 Boccarusso L, De Fazio D, Durante M (2022) Production of PP composites reinforced with flax and hemp woven mesh fabrics via compression molding. Inventions 7:. https://doi.org/10.3390/inventions7010005 Durante M, Formisano A, Lambiase F (2018) Incremental forming of polycarbonate sheets. J Mater Process Technol 253:57–63. https://doi.org/10.1016/j.jmatprotec.2017.11.005 Formisano A, Boccarusso L, De Fazio D, Durante M (2024) Effects of toolpath on defect phenomena in the incremental forming of thin polycarbonate sheets. Int J Adv Manuf Technol 133:4957–4966. https://doi.org/10.1007/s00170-024-14047-z Bagudanch I, Garcia-Romeu ML, Sabater M (2016) Incremental forming of polymers: Process parameters selection from the perspective of electric energy consumption and cost. J Clean Prod 112:1013–1024. https://doi.org/10.1016/j.jclepro.2015.08.087 Formisano A, Fazio D De, Irace G, Durante M (2025) Incremental Forming of Natural Fiber-Reinforced Polypropylene Composites: Considerations on Formability Limits and Energy Consumption. Mater 2025, Vol 18, Page 2688 18:2688. https://doi.org/10.3390/MA18122688 Durante M, Formisano A, Lambiase F (2019) Formability of polycarbonate sheets in single-point incremental forming. Int J Adv Manuf Technol 102:2049–2062. https://doi.org/10.1007/s00170-019-03298-w Cite Share Download PDF Status: Published Journal Publication published 17 Dec, 2025 Read the published version in The International Journal of Advanced Manufacturing Technology → Version 1 posted Editorial decision: Major Revisions Needed 05 Sep, 2025 Reviewers agreed at journal 16 Jun, 2025 Reviewers invited by journal 16 Jun, 2025 Editor assigned by journal 16 Jun, 2025 First submitted to journal 13 Jun, 2025 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. 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Formisano","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwklEQVRIiWNgGAWjYDAC5gNAwoCBgR9IgZg8hLWwJUC0SDZAtRDWA9YC0nUAKkBQC38b87FPNwrq5I1v5B48XFDDIGNPSIvEMbbk2TkGhw233chLODzjGDEOu99jzJxjcIBx2w2gRh42IrTIH+MBaamz3zwDpOUfEVoMIFqYEzdIALXwthGhxRDoF6CWw8kzzrwBaumT4OE5QECL3DHmw8w5f+ps+9tzjD/zfLOxZ28gZA0akCBR/SgYBaNgFIwCrAAA8R83qQ7DCnoAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-4909-8315","institution":"Universita degli Studi di Napoli Federico II","correspondingAuthor":true,"prefix":"","firstName":"Antonio","middleName":"","lastName":"Formisano","suffix":""},{"id":472205669,"identity":"4682c457-daed-41f7-a433-a5f9f9314918","order_by":1,"name":"Dario De Fazio","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Dario","middleName":"","lastName":"De Fazio","suffix":""},{"id":472205670,"identity":"70870227-b7fb-47f0-8718-4bf723bb263d","order_by":2,"name":"Antonio Langella","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Antonio","middleName":"","lastName":"Langella","suffix":""},{"id":472205671,"identity":"81865e05-8af8-4305-86af-542b52452dc5","order_by":3,"name":"Martina Panico","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Martina","middleName":"","lastName":"Panico","suffix":""},{"id":472205672,"identity":"8d1983d6-354e-4890-84a2-35e1876ef49d","order_by":4,"name":"Massimo Durante","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Massimo","middleName":"","lastName":"Durante","suffix":""}],"badges":[],"createdAt":"2025-06-13 08:48:42","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-6886441/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-6886441/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s00170-025-17158-3","type":"published","date":"2025-12-17T15:57:23+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":84924293,"identity":"9e5801bd-e2cc-467f-8e23-5841762fe69d","added_by":"auto","created_at":"2025-06-18 21:18:54","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":550116,"visible":true,"origin":"","legend":"\u003cp\u003eOperations for the manufacture of composite laminates.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/c58977aa394cf38f324873a2.png"},{"id":84924294,"identity":"ffdc3823-23b6-4e8c-8c1e-caf802ddbb5e","added_by":"auto","created_at":"2025-06-18 21:18:54","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":467105,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of spherical caps (a) and of the forming processes (b).\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/ef69129e998a2f05b61c0f64.png"},{"id":84925126,"identity":"cf05a028-6f4a-4321-9b17-3d0ddf09069c","added_by":"auto","created_at":"2025-06-18 21:42:55","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":1159131,"visible":true,"origin":"","legend":"\u003cp\u003eEquipment for NIF (a) and SF tests (b).\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/660f99e6a5aa1705ec79e421.png"},{"id":84924726,"identity":"bfa45a61-640e-40f5-9e48-4c72c5bd00b8","added_by":"auto","created_at":"2025-06-18 21:26:54","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":236539,"visible":true,"origin":"","legend":"\u003cp\u003eRepresentation of the toolpath for the NIF processes.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/f79b651858f4bbfc6d39350c.png"},{"id":84924305,"identity":"40e1d4d6-3cf0-4650-a051-d4944ddb5167","added_by":"auto","created_at":"2025-06-18 21:18:55","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":377547,"visible":true,"origin":"","legend":"\u003cp\u003eSpherical cap (\u003cem\u003ea\u003c/em\u003e = 40 mm and \u003cem\u003eθ\u003c/em\u003e = 50°) by NIF\u003csub\u003ePD\u003c/sub\u003e test.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/88de804daee9fb0fde07ab5e.png"},{"id":84924298,"identity":"0d178adf-bfcb-4ff9-a945-5fe9e7ca0ebd","added_by":"auto","created_at":"2025-06-18 21:18:54","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":66899,"visible":true,"origin":"","legend":"\u003cp\u003eExperimental and designed profiles of the spherical caps.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/e2a5d6f5c4acca38547dfef9.png"},{"id":84924796,"identity":"400b23ec-26f4-435e-b9e6-1c8699539d6d","added_by":"auto","created_at":"2025-06-18 21:34:55","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":555208,"visible":true,"origin":"","legend":"\u003cp\u003eSpherical cap (\u003cem\u003ea\u003c/em\u003e = 20 mm and \u003cem\u003eθ\u003c/em\u003e = 70°) manufactured by NIF\u003csub\u003e0\u003c/sub\u003e test (a) and failures from SF\u003csub\u003e0\u003c/sub\u003e test (b).\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/8c7bcfd0f0d0c70bb2226998.png"},{"id":84924734,"identity":"0d85d989-e260-4a7c-ad1c-03f97f231d2c","added_by":"auto","created_at":"2025-06-18 21:26:55","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":519051,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT\u003c/em\u003e\u003c/sub\u003e trends for NIF (a) and SF tests (b).\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/d4371a244d8ac9f46bf78e66.png"},{"id":84924301,"identity":"38757f20-7a16-4a14-b536-1e33a2d15268","added_by":"auto","created_at":"2025-06-18 21:18:54","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":449790,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eP\u003c/em\u003e trends for NIF (a) and SF tests (b).\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/835a77fddafb7696a30b30e3.png"},{"id":84924798,"identity":"8bd857cb-a76c-4931-89b8-97a491aa470d","added_by":"auto","created_at":"2025-06-18 21:34:55","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":309229,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eE\u003c/em\u003e trends for NIF (a) and SF tests (b).\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/110548829d0ce0709add18f4.png"},{"id":98813899,"identity":"f5700252-9964-460b-abda-0cc94c178f99","added_by":"auto","created_at":"2025-12-22 16:06:56","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":7096092,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-6886441/v1/d9c9fb65-b164-4453-af6a-46a53104fe78.pdf"}],"financialInterests":"","formattedTitle":"Comparison between Cold Incremental and Stretch Forming of Flax Fiber-Reinforced Polypropylene Composites","fulltext":[{"header":"Introduction","content":"\u003cp\u003eIncremental sheet forming (ISF) is a technique that, in its simplest variant, known as negative incremental forming (NIF), involves the incremental deformation of a clamped sheet through the progressive action of a simple and non-dedicated forming tool, driven by a CNC machine to obtain the desired final shape [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Its layered manufacturing strategy matches well with the production of customized and free-form parts [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e], finding application in several industrial fields such as aerospace [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e], automotive [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], and medical [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] applications, and so on. Many studies have been conducted to compare ISF with other conventional sheet forming processes. They have highlighted some unique ISF characteristics, such as reduced tooling, cost-effectiveness, short setup time, high formability and flexibility, low environmental impact, but also high process time and geometric inaccuracies due to the absence of counter dies [\u003cspan additionalcitationids=\"CR9 CR10\" citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eISF was originally conceived and subsequently developed for metal and metal alloy sheets, as evidenced by several works [\u003cspan additionalcitationids=\"CR13 CR14\" citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Recently, research on ISF has shown increased interest in non-metallic materials like thermoplastic polymers and composites. While ISF of thermoplastics, whose properties make them widely used for mass production [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e], has been investigated in several studies [\u003cspan additionalcitationids=\"CR18\" citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], demonstrating its potential to replace the traditional processes based on repetitive heating, shaping, and cooling actions [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e], research on the ISF of composite materials remains limited. Starting from preliminary works [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e] and arriving at advances in ISF of polymer-based composites reinforced with glass [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] and carbon fibers [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e], it is clear that ISF can represent a sustainable and cost-effective way for composite forming [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eAn area of significant interest in recent years, both in research and on an industrial scale, is the use of natural fibers (from seeds, stems or roots) as reinforcements for polymer composites [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. These fibers represent a low-cost, biodegradable, renewable, and nontoxic alternative to the most common synthetic reinforcements (glass and carbon fibers) [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. They enhance certain properties of commercial polymers, may contribute to lowering the energy demand during processing, and make them semi-biodegradable [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Hemp and flax are the strongest and stiffest natural fibers [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e], as well as two of the most popular and widely available fibers in European countries. They are composed of a complex microstructure consisting of bundles of twisted elementary fibers that are glued together by an amorphous matrix of pectin, hemicelluloses, and lignin [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. These fibers exhibit excellent vibration damping properties, as well as low density and high specific stiffness compared to glass or aramid fibers, and are commonly used for the manufacture of biocomposites [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThermoplastics as composite matrices are used in many fields, such as automotive [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], aeronautics [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e], and biomedical [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e] applications; they show some significant advantages compared to thermosets, in terms of short process time, potential recyclability, and the possibility to be remodeled at high temperatures [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Polypropylene (PP) is the world's second-most widely produced synthetic polymer. Thanks to its high chemical and wear resistance, excellent mechanical properties, ease of processing, and cost-effectiveness [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e], it finds application in automotive parts, reusable containers, packaging, and laboratory equipment [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e], as well as for advanced composites in aerospace, civil, and automotive fields [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. In addition, along with polyethylene and polyvinyl chloride, PP currently dominates as a matrix for natural composites [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe adhesion between the matrix and fibers plays an essential role in the stress transfer of composites. Poor adhesion in natural fiber-reinforced polymers can be improved by chemical fiber pretreatments; the most common are alkaline and silane treatments, but isocyanate, peroxide, acetylation and maleic treatments have also been analyzed [\u003cspan additionalcitationids=\"CR44\" citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Alternatively, another chemical solution involves adding a coupling agent to the matrix; the most common agent for natural fiber-reinforced PP composites is maleic anhydride-grafted polypropylene [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. Together with chemical treatments, another viable way to improve the natural fibers/polymer matrix interaction is the use of reinforcements in the form of fabrics to generate a mechanical coupling. This solution, already considered for metal foams [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e] and sandwich structures [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e], can be considered for thermoplastics reinforced with natural fibers in the form of fabric by using the compression molding technique [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]; the main process parameters that influence the composite performance are the temperature, the dwelling time, and the molding pressure.\u003c/p\u003e \u003cp\u003eThis work presents an experimental campaign based on ISF and stretch forming (SF) tests, with and without a partial counter die, for the manufacture of spherical caps, starting from natural fiber-reinforced PP composites. The laminates were manufactured by compression molding using flax woven fabrics, but without fiber treatments or coupling agents; these further production steps would have increased the manufacturing process time and costs, as well as decreased the environmental benefits associated with the use of flax fibers. The forming processes were conducted without localized heating [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e] and without using full counter dies to preserve the flexibility and ease of use of the ISF process. Despite not allowing for very high wall angles [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e], this process can be used for applications such as shaping stiffening ribs for panels in the automotive, aviation, and naval fields [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]; consequently, a component like a spherical cap, with decreasing wall angle and deformation states, was chosen. Through the acquisition of the cap profiles and the evaluation of formability, forming forces, power, and energy consumption, the experimental campaign highlights the benefits and drawbacks of using ISF, compared to SF process, for these biobased composites.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003eThis section describes the manufacturing process of the composite laminates, the forming of the spherical caps, and the features evaluated for comparing between the two forming procedures.\u003c/p\u003e\n\u003cdiv id=\"Sec3\"\u003e\n \u003ch2\u003eManufacture of the laminates\u003c/h2\u003e\n \u003cp\u003eThe composite laminates used in this study (area of 200 \u0026times; 150 mm\u003csup\u003e2\u003c/sup\u003e, thickness of 2.2 mm) were manufactured using neat PP films (supplied by GDC S.r.l.; thickness of 0.5 mm and density of 0.92 g/cm\u003csup\u003e3\u003c/sup\u003e) and a woven fabric of flax, supplied by FIDIA S.r.l. - Technical Global Services. The fabric had a mass per unit area of 320 g/cm\u003csup\u003e2\u003c/sup\u003e, a tex number of 324 g/km, and was safely stored in a polymeric bag under vacuum at 20\u0026deg;C and 45% humidity. As previously mentioned, it was not subjected to any previous chemical or surface treatment. Before the molding process, it was dried at 60\u0026deg;C for 12 hours to eliminate any trace of humidity. A figure of the fabric and a magnification of a single yarn constituted by the winding of filaments are shown in [\u003cspan\u003e53\u003c/span\u003e], while their main properties are summarized in [\u003cspan\u003e51\u003c/span\u003e].\u003c/p\u003e\n \u003cp\u003eThe laminates were produced using a conventional compression molding press, considering the stacking sequence (five layers with a symmetric layup; the first and the last two layers were PP films, while the central layer was flax fabric) and following the operations schematized in Fig. \u003cspan\u003e1\u003c/span\u003e. Specifically, the molding temperature was 200\u0026deg;C, and the total molding time was 300 s, with the first 120 s being the dwelling time, a waiting period after which the plates were closed, applying a pressure of 4 MPa for the remaining 180 s. The choice of a woven fabric with a large mesh size and the process parameters mentioned above proved to be an effective solution for the manufacture of flax and hemp fiber-reinforced PP composites, even with a different stacking sequence [\u003cspan\u003e53\u003c/span\u003e]. Compared to unreinforced PP, these composites showed notable improvements in tensile and bending properties, as well as higher bearing capacities and service temperatures.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eForming tests\u003c/h3\u003e\n\u003cp\u003eSpherical caps (see the schematization in Fig. 2a, where \u003cem\u003ea\u003c/em\u003e and \u003cem\u003e\u0026theta;\u003c/em\u003e denote the base radius and the polar angle, respectively) were manufactured using cold NIF and SF processes (see Fig. 2b and Fig. \u003cspan\u003e3\u003c/span\u003e for a schematization and the actual equipment of the tests); the forming tests were conducted using a C.B. Ferrari high-speed four-axis vertical machining center.\u003c/p\u003e\n\u003cp\u003eThe laminates were secured using a clamping frame with a square working area of 100 \u0026times; 100 mm\u003csup\u003e2\u003c/sup\u003e. To reduce the sheet bending defect close to the base of the cap, the tests were also conducted using a hollow cylinder as a partial counter die; differently from a full counter die, it only supports the essential areas of the sheet, allowing to manufacture components with some similarities and preserving the process flexibility. Additionally, the probability of failures and defects was reduced by carrying out the tests under lubricated conditions, using Boelube 70104 (100A) synthetic lubricant, developed by Boeing and supplied by Orelube.\u003c/p\u003e\n\u003cp\u003eThe incremental and stretch forming tests without partial counter die are labelled as NIF\u003csub\u003e0\u003c/sub\u003e and SF\u003csub\u003e0\u003c/sub\u003e, respectively, while the corresponding ones with partial counter die as NIF\u003csub\u003ePD\u003c/sub\u003e and SF\u003csub\u003ePD\u003c/sub\u003e, respectively. Two tests for each different case were performed.\u003c/p\u003e\n\u003cdiv\u003e\n\u003c/div\u003e\n\u003cp\u003eFor the NIF tests (see Fig. \u003cspan\u003e3\u003c/span\u003ea), a non-rotating stainless-steel stylus with a hemispherical head, 10 mm in diameter, was driven by the CNC machine at a nominal speed \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003eNIF\u003c/em\u003e\u003c/sub\u003e = 1000 mm/min to impose progressive deformation on the laminate. The tool followed a path with helical turns that alternated in anticlockwise and clockwise directions. This approach, based on observations for metal [\u003cspan\u003e12\u003c/span\u003e] and polycarbonate ISF parts [\u003cspan\u003e54\u003c/span\u003e], significantly reduced the probability of twisting, as the twist produced in one turn is almost completely recovered in the next [\u003cspan\u003e55\u003c/span\u003e]. Figure 4 shows a not-to-scale representation of some turns of the toolpath; \u003cem\u003e\u0026theta;s\u003c/em\u003e\u0026thinsp;=\u0026thinsp;1\u0026deg; is the angular step down, i.e., the angular distance described after one complete turn.\u003c/p\u003e\n\u003cp\u003eFor the SF tests (see Fig. \u003cspan\u003e3\u003c/span\u003eb), the machine simply imposed on the die a vertical displacement, equal to the cap height (equal to 18.65 mm), at a nominal speed \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003eSF\u003c/em\u003e\u003c/sub\u003e = 60 mm/min.\u003c/p\u003e\n\u003ch3\u003eMeasured features\u003c/h3\u003e\n\u003cp\u003eTo evaluate the geometrical accuracy of the processes, the shape of the caps was measured using a Zeiss DuraMax coordinate measuring machine (measurement accuracy of 2.4 \u0026micro;m) and Calypso software and then compared to the target geometry. A ruby sphere stylus with a diameter of 3.0 mm was used for the measurements. Each measurement involved 450 individual points evenly distributed across the diagonals AC and BD (see Fig.\u0026nbsp;2a).\u003c/p\u003e\n\u003cp\u003eTo estimate the magnitude of the forming loads, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eX\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eY\u003c/em\u003e\u003c/sub\u003e, and \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eZ\u003c/em\u003e\u003c/sub\u003e forces were acquired at 50 Hz by the K-MCS10 multicomponent sensor (fixed between the clamping fixture and the base plate of the CNC machine, see Fig. \u003cspan\u003e3\u003c/span\u003e), equipped with the QuantumX MX840B data acquisition system and the Catman Easy AP software. From their combination, the magnitudes of the force in the \u003cem\u003eXY\u003c/em\u003e plane and of the total forming force (labelled as \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eXY\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT\u003c/em\u003e\u003c/sub\u003e, respectively) were also obtained.\u003c/p\u003e\n\u003cp\u003eThe forces also enabled the measurement of power (\u003cem\u003eP\u003c/em\u003e) and energy consumption (\u003cem\u003eE\u003c/em\u003e). Unlike the evaluation of the electrical energy, the use of forces allows for the estimation of the actual energy required for the process, which represents only a small fraction of the total energy consumed, as most of the energy demand is associated with auxiliary functions of the equipment [\u003cspan\u003e56\u003c/span\u003e].\u003c/p\u003e\n\u003cp\u003eFor the NIF tests, \u003cem\u003eP\u003c/em\u003e was obtained by only considering the contribution of \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eXY\u003c/em\u003e\u003c/sub\u003e, according to the following equation:\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e \u0026thinsp; \u003cspan name=\"Emphasis\"\u003e\u0026asymp;\u003c/span\u003e \u0026thinsp; \u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003eXY\u003c/em\u003e\u003c/sub\u003e = \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eXY\u003c/em\u003e\u003c/sub\u003e ∙ \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003eNIF\u003c/em\u003e\u003c/sub\u003e (1)\u003c/p\u003e\n\u003cp\u003eThis simplification is possible because, for the NIF processes, \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003eNIF\u003c/em\u003e\u003c/sub\u003e can be approximated with the speed in the \u003cem\u003eXY\u003c/em\u003e plane, due to the low \u003cem\u003e\u0026theta;s\u003c/em\u003e value that makes the path almost horizontal, while the speed along the \u003cem\u003eZ\u003c/em\u003e axis is very low and does not significantly contribute to the total power and energy. This was observed in a previous study by the authors on NIF of cones and spherical caps starting from laminates of flax and hemp fiber-reinforced PP composites [\u003cspan\u003e57\u003c/span\u003e]; the simplification resulted in an underestimation in terms of energy of less than 2.5% in the worst case.\u003c/p\u003e\n\u003cp\u003eFor the SF tests, \u003cem\u003eP\u003c/em\u003e was determined by:\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u0026thinsp;=\u0026thinsp;\u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eZ\u003c/em\u003e\u003c/sub\u003e ∙ \u003cem\u003ev\u003c/em\u003e\u003csub\u003e\u003cem\u003eSF\u003c/em\u003e\u003c/sub\u003e (2)\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eE\u003c/em\u003e trends were determined as time-integrals of the \u003cem\u003eP\u003c/em\u003e curves. The Riemann integral was used, with a regular partition of the time interval equal to 0.02 s, i.e. the period of acquisition of the forces.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cp\u003eThis section summarizes and discusses the main results of the experimental campaign. The first part addresses the feasibility and geometric accuracy of the processes, while the second part analyzes the forming forces, power, and energy. Given the limited variability observed among repetitions, only representative curves and average values of the investigated features are reported for the sake of conciseness.\u003c/p\u003e\n\u003ch3\u003eFeasibility and geometrical accuracy\u003c/h3\u003e\n\u003cp\u003eSpherical caps with \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;40 mm and \u003cem\u003e\u0026theta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;50\u0026deg; were manufactured using NIF and SF processes, with and without a partial die (with internal and external diameters of 80 and 100 mm, respectively). In all cases, the parts were sound and had good surface quality; moreover, non-severe working conditions were achieved, as highlighted by the lack of instabilities and wrinkling [\u003cspan\u003e58\u003c/span\u003e]. An NIF\u003csub\u003ePD\u003c/sub\u003e cap is reported in Fig. \u003cspan\u003e5\u003c/span\u003e.\u003c/p\u003e\n\u003cp\u003eFigure \u003cspan\u003e6\u003c/span\u003e shows the actual and the target cap shapes (for easy reading, only half of the experimental profiles are reported). Two features were evaluated to estimate the geometrical accuracy of the forming processes, i.e. the difference in maximum height (\u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e) and the gap in correspondence of the intersection between the base of the cap and the flange (\u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e); Table \u003cspan\u003e1\u003c/span\u003e summarizes these values.\u0026nbsp;\u003c/p\u003e\n\u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 1\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003e\u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e values for the geometrical accuracy of the forming processes.\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eFeature\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eTest\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNIF\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNIF\u003csub\u003ePD\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSF\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSF\u003csub\u003ePD\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e13.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e12.8\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e [mm]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"char\"\u003e\n \u003cp\u003e2.6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eThe NIF process guaranteed a more accurate geometrical quality due to the incremental and localized nature of the deformation mechanism, and the use of the partial die improved it, particularly near the clamped zone; in contrast, the SF process proved to be completely ineffective, in both the variants. The stretching mechanism proved to be unsuitable for these geometries when starting from cold laminates, resulting primarily inelastic deformations that were almost entirely recovered after processing. The low formability efficiency of the SF processes was further confirmed by more severe forming tests to obtain spherical caps with \u003cem\u003ea\u003c/em\u003e\u0026thinsp;=\u0026thinsp;20 mm and \u003cem\u003e\u0026theta;\u003c/em\u003e\u0026thinsp;=\u0026thinsp;70\u0026deg; (see Fig. 7). While the NIF tests were concluded without incurring failures (Fig. 7a), the SF tests failed, as highlighted in Fig. 7b.\u003c/p\u003e\n\u003cdiv id=\"Sec8\"\u003e\n \u003ch2\u003eForces, power, and energy\u003c/h2\u003e\n \u003cp\u003eFigure 8 reports the trends of \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT\u003c/em\u003e\u003c/sub\u003e. Concerning the NIF tests (Fig.\u0026nbsp;8a), the fluctuations of the trends reflected the alternating nature of the toolpath. The initial part of the NIF\u003csub\u003ePD\u003c/sub\u003e curve had a higher slope, due to the contact of the laminate with both the tool and the counter die, which made the system highly stiff. This resulted in reduced \u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003edh\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e values, as the flange acted as a weak constraint in NIF\u003csub\u003e0\u003c/sub\u003e, compared to the more effective action provided by the counter die in NIF\u003csub\u003ePD\u003c/sub\u003e. The curves reached their maximum value, corresponding to the condition of maximum tool/sheet contact, during which the processes exhibited their most effective incremental deformation of the laminates. The final part of the curves showed a decreasing trend, as a consequence of the less severe working conditions encountered when the tool reached the top of the caps, due to the decreasing wall angle. Figure 8b reports \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT\u003c/em\u003e\u003c/sub\u003e trends when using the SF processes. The forces continuously increased, because of the increasing contact area between the die and the laminate as the tool displacement increased. But they did not result effective in terms of formability, as observed by Fig. \u003cspan\u003e6\u003c/span\u003e.\u003c/p\u003e\n \u003cp\u003eFigure 9 reports the power curves. They obviously followed the same trend of the forming forces, both for NIF (Fig.\u0026nbsp;9a) and SF tests (Fig.\u0026nbsp;9b), since they were obtained by multiplying them and constant values of velocity.\u003c/p\u003e\n \u003cp\u003eFinally, Fig. 10 reports the energy curves. They showed an increasing trend, because they were obtained by integrating the power curves.\u003c/p\u003e\n \u003ctable id=\"Tabd\" border=\"1\"\u003e\n \u003cthead\u003e\n \u003ctr\u003e\u003c/tr\u003e\n \u003c/thead\u003e\n \u003c/table\u003e\n \u003cp\u003e\u003c/p\u003e\n \u003cp\u003eTable \u003cspan\u003e2\u003c/span\u003e summarizes the results of this subsection, reporting the maximum values of \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eP\u003c/em\u003e and \u003cem\u003eE\u003c/em\u003e. In all cases, higher values were recorded when using the partial counter die, because of a higher stiffness of the system. The low forming forces for NIF processes confirmed the above predicted non-severe working conditions and the usability of non-dedicated tools and machines. This was not true for SF processes, for which the higher values of forces reached did not guarantee forming efficiency. Both NIF and SF processes required low and similar power levels, while the energy for NIF processes, compared to SF, was higher due to the high process time but guaranteed a good formability.\u0026nbsp;\u003c/p\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv\u003eTable 2\u003c/div\u003e\n \u003cdiv\u003e\n \u003cp\u003eMaximum values of \u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT\u003c/em\u003e\u003c/sub\u003e, \u003cem\u003eP\u003c/em\u003e and \u003cem\u003eE\u003c/em\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eFeature\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\" colspan=\"4\"\u003e\n \u003cp\u003eTest\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNIF\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNIF\u003csub\u003ePD\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSF\u003csub\u003e0\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eSF\u003csub\u003ePD\u003c/sub\u003e\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eF\u003c/em\u003e\u003csub\u003e\u003cem\u003eTOT,MAX\u003c/em\u003e\u003c/sub\u003e [N]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e473\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e536\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3621\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6313\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eP\u003c/em\u003e\u003csub\u003e\u003cem\u003eMAX\u003c/em\u003e\u003c/sub\u003e [W]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e2.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e3.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.3\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cem\u003eE\u003c/em\u003e\u003csub\u003e\u003cem\u003eMAX\u003c/em\u003e\u003c/sub\u003e [J]\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e441.0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e563.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e21.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e34.2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n\u003c/div\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThis work compares the incremental and the stretch forming applied to laminates of flax woven fabric-reinforced polypropylene composites, obtained by compression molding and without fiber treatments or coupling agents; the processes for the manufacture of spherical caps were carried out at room temperature, without and with a partial counter die.\u003c/p\u003e \u003cp\u003eFrom the comparison of the geometric profiles, the incremental forming process results effective for obtaining the designed components, especially when using the partial counter die, due to the incremental and localized approach that guarantees good deformation levels also under cold working conditions; on the other hand, stretch forming proves to be highly ineffective, while using the partial counter die, with the prevalence of the elastic response of the laminates.\u003c/p\u003e \u003cp\u003eThe forming force levels for the incremental forming are extremely limited and this translates into non-severe working conditions and reduced risks for the equipment, differently from what observed for the stretch forming.\u003c/p\u003e \u003cp\u003eBoth the processes require very low power; the higher but however limited energy levels for the incremental forming process reflect the high process time, one of the main cons of this technique.\u003c/p\u003e \u003cp\u003eFuture research could consider the evaluation of the mechanical properties of the components, and the feasibility of remolding panels after incremental forming. In addition, and according to a sustainable manufacturing perspective, it could be of interest to investigate the incremental forming of completely natural composite laminates.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eDeclaration of generative AI and AI-assisted technologies in the writing process\u003c/p\u003e\n\u003cp\u003eDuring the preparation of this work the author(s) used Copilot in order to improve its readability. After using this tool/service, the author(s) reviewed and edited the content as needed and take(s) full responsibility for the content of the publication.\u003c/p\u003e\u003cp\u003eFunding\u003c/p\u003e\n\u003cp\u003eThe authors declare that no funds, grants, or other support were received during the preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003eCompeting Interests\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection, and analysis were performed by Antonio Formisano, as well as the writing of the first draft of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eFormisano A, Boccarusso L, Capece Minutolo F, et al (2017) Negative and positive incremental forming: Comparison by geometrical, experimental, and FEM considerations. Mater Manuf Process 32:530\u0026ndash;536. https://doi.org/10.1080/10426914.2016.1232810\u003c/li\u003e\n\u003cli\u003eFormisano A, Astarita A, Boccarusso L, et al (2022) Formability and surface quality of non-conventional material sheets for the manufacture of highly customized components. Int J Mater Form 15:1\u0026ndash;11. https://doi.org/10.1007/S12289-022-01663-x\u003c/li\u003e\n\u003cli\u003eHussain G, Khan HR, Gao L, Hayat N (2013) Guidelines for tool-size selection for single-point incremental forming of an aerospace alloy. 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J Mater Process Technol 253:57\u0026ndash;63. https://doi.org/10.1016/j.jmatprotec.2017.11.005\u003c/li\u003e\n\u003cli\u003eFormisano A, Boccarusso L, De Fazio D, Durante M (2024) Effects of toolpath on defect phenomena in the incremental forming of thin polycarbonate sheets. Int J Adv Manuf Technol 133:4957\u0026ndash;4966. https://doi.org/10.1007/s00170-024-14047-z\u003c/li\u003e\n\u003cli\u003eBagudanch I, Garcia-Romeu ML, Sabater M (2016) Incremental forming of polymers: Process parameters selection from the perspective of electric energy consumption and cost. J Clean Prod 112:1013\u0026ndash;1024. https://doi.org/10.1016/j.jclepro.2015.08.087\u003c/li\u003e\n\u003cli\u003eFormisano A, Fazio D De, Irace G, Durante M (2025) Incremental Forming of Natural Fiber-Reinforced Polypropylene Composites: Considerations on Formability Limits and Energy Consumption. Mater 2025, Vol 18, Page 2688 18:2688. https://doi.org/10.3390/MA18122688\u003c/li\u003e\n\u003cli\u003eDurante M, Formisano A, Lambiase F (2019) Formability of polycarbonate sheets in single-point incremental forming. Int J Adv Manuf Technol 102:2049\u0026ndash;2062. https://doi.org/10.1007/s00170-019-03298-w\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":true,"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":"Incremental Forming, Stretch Forming, Polypropylene, Flax, Geometrical Accuracy, Forces, Energy","lastPublishedDoi":"10.21203/rs.3.rs-6886441/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-6886441/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eIncremental sheet forming, born as a versatile and cost-effective alternative to traditional procedures to deform incrementally and without dedicated dies flat metal sheets into complex three-dimensional shapes, has recently been gaining attention as a forming technique for polymers and composites. Among these, natural fiber-reinforced thermoplastics have been climbing in popularity because natural fibers are widely available, act as effective polymer reinforcement, and make the composite semi-biodegradable. Through compression molding and using natural woven fabrics, it is also possible to achieve good fiber/matrix coupling without compromising the environmental benefits with chemical coupling agents and/or treatments. This experimental study compares cold incremental and stretch forming processes of flax woven fabric-reinforced polypropylene composites for the manufacture of spherical caps. By considering formability, geometrical accuracy, forming forces, power, and energy consumption, the study highlights the effectiveness of incremental forming applied to these biobased composites, without resorting to full counter dies and heating stages.\u003c/p\u003e","manuscriptTitle":"Comparison between Cold Incremental and Stretch Forming of Flax Fiber-Reinforced Polypropylene Composites","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-06-18 21:18:50","doi":"10.21203/rs.3.rs-6886441/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Major Revisions Needed","date":"2025-09-05T15:19:32+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2025-06-17T01:38:18+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-06-16T22:04:47+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-06-16T10:00:10+00:00","index":"","fulltext":""},{"type":"submitted","content":"The International Journal of Advanced Manufacturing Technology","date":"2025-06-13T04:48:13+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":"1593715b-19d8-4735-8e83-9e11db764e03","owner":[],"postedDate":"June 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-12-22T16:00:22+00:00","versionOfRecord":{"articleIdentity":"rs-6886441","link":"https://doi.org/10.1007/s00170-025-17158-3","journal":{"identity":"the-international-journal-of-advanced-manufacturing-technology","isVorOnly":false,"title":"The International Journal of Advanced Manufacturing Technology"},"publishedOn":"2025-12-17 15:57:23","publishedOnDateReadable":"December 17th, 2025"},"versionCreatedAt":"2025-06-18 21:18:50","video":"","vorDoi":"10.1007/s00170-025-17158-3","vorDoiUrl":"https://doi.org/10.1007/s00170-025-17158-3","workflowStages":[]},"version":"v1","identity":"rs-6886441","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-6886441","identity":"rs-6886441","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}