Water Jet Guided Laser Cutting of Thick Section Glass Fibre Reinforced Polymer

Water Jet Guided Laser Cutting of Thick Section Glass Fibre Reinforced Polymer | 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 Water Jet Guided Laser Cutting of Thick Section Glass Fibre Reinforced Polymer Ben Mason, Helen Elkington, Kursad Sezer, Sundar Marimuthu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4630208/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Laser cutting is well established for cutting metals, alloys, and ceramics. However, its application for cutting fibre reinforced polymer composites is constrained due to specific challenges. The distinct optical and thermal properties of the fibres and matrix often lead to excessive thermal damage. Thick-section laser cutting of composites is an especially challenging task. The water jet guided laser (WJGL), employing a hair-thin water jet to guide the laser, has proven successful for such challenging materials. Thermal damage is minimized by effective in-situ cooling of the interaction zone by the water flow. This work evaluates the feasibility of WJGL cutting glass fiber reinforced polymer (GFRP). A WJGL system, fitted with a 400 W green nanosecond laser, was used to cut 7.5 mm thick GFRP using a multi-pass strategy. Effective cutting speeds of up to 10.1 mm/min were obtained with an average wall taper of 1.91°. Improvements in taper angle were realised via reduced effective cutting speeds (0.81°, 7.5 mm/min). Defects including charring, edge chipping, and matrix discolouration were observed. These results show that while the WJGL can cut thick GFRP with minimal defects, further work is required to enhance the productivity before the technique could be viable for widespread adoption. Water Jet Guided Laser Glass Fibre Reinforced Polymer Laser Cutting Thick Section Cutting Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Glass fibre reinforced polymer (GFRP) is an attractive material due to its higher specific strength and stiffness than metals, and significantly reduced cost compared to carbon fibre reinforced polymer (CFRP). It is commonly used in many engineered structures, from wind turbines to sportscars and watercraft. However, like all fibre reinforced polymer composites, while the manufacturing is nearly net-shape, there are still certain machining operations required to achieve the desired shape. Traditional machining (drilling, milling, etc.) suffer from accelerated tool wear [ 1 ] and can lead to material damage such as delamination and edge chipping [ 2 ]. Therefore, non-conventional cutting methods have gained much attention in recent years. Abrasive water jet (AWJ) has been investigated for cutting CFRP, with most researchers finding strong links between the fibre orientation [ 3 ] and jet pressure [ 4 ] with the achievable cut quality. Wire electro-discharge machining (W-EDM) is another candidate for cutting CFRP [ 5 ], however is unsuitable for GFRP due to the materials electrical insulating properties. There has been comparatively little interest in cutting of GFRP using such nonconventional techniques. Laser cutting has been extensively researched for cutting CFRP, and to a lesser extent GFRP, as it addresses the problems of the previously mentioned technologies. Specifically, no tool wear, negligible force applied to the material, and a reduced risk of material damage. Shyha [ 6 ] found a higher material removal rate (MRR) for laser cutting of GFRP than CFRP, but with a more complex relationship to scan speed. It has been repeatedly found that when laser cutting GFRP, the cutting efficiency shows nonlinear relationships with both laminate thickness [ 7 ] and laser power [ 8 ], complicating process optimization. Further insight is offered by the research into laser cutting of CFRP. For example, shorter pulse durations are preferable for minimizing the heat affected zone (HAZ) [ 9 ] and while higher average power enables faster cutting speeds and thus reduced HAZ, it increases the risk of bridging (small regions of uncut material at the cut exit) [ 10 ]. Therefore, it is clear that a processing window exists where full cuts can be achieved with an acceptable HAZ to reach a target cutting speed. It has also been suggested that different laminate constructions (in terms of fibre orientation, matrix material, fibre content, etc.) may require bespoke optimizations [ 11 ]. The water jet guided laser (WJGL) technology uses a narrow, laminar jet of water to guide the laser beam to the workpiece. The concept is shown diagrammatically in Fig. 1 . The water does not contribute directly to the cutting action, only to maintain a consistent beam width [ 12 ] (no divergence) and to cool the cut material [ 13 ]. Therefore, the resulting long, narrow, cylindrical beam enables thick section cutting of various materials [ 14 ] with minimal HAZ [ 15 ]. An added effect is the continuous water flow effectively evacuates molten material and other debris, preventing spatter [ 13 ]. There is no current literature regarding WJGL cutting of GFRP, with more effort focused on cutting CFRP. For example, Sun et al. [ 15 ] used a 10 W nanosecond UV laser to cut 1 mm thick (5 ply) CFRP with both WJGL and conventional lasers. They found WJGL to be approximately 50 × slower than the conventional laser, in part due to attenuation within the water jet and the larger effective spot size (10 ×). Wu et al. [ 17 ] used a 60 W nanosecond green WJGL to cut 1 mm thick CFRP, achieving a relatively high effective cutting speed of 75 mm/min. While processing thicker sections, the use of parallel scanning was required to ensure jet integrity. There is little information regarding high-power WJGL cutting of CFRP, with one such example from Sun et al. [ 18 ] who used a 350 W microsecond source for cutting 0.5 mm thick (4 ply) CFRP, finding different scanning strategies (e.g. parallel paths) could greatly improve the cut surface quality at the expense of processing speed. Finally, Elkington et al. [ 19 ] evaluated the influence of various process parameters (laser power, pulse frequency, and jet pressure) on cut speed and wall taper, using a green nanosecond source, operating at between 130 W and 270 W. Overall, WJGL cutting of CFRP has shown to have reduced productivity compared to alternative techniques, but with improved cut quality. It is likely that with higher power lasers, maximum cutting rates and thicknesses will only increase, potentially making WJGL cutting a compelling option for processing very thick composites, such as GFRP, or processing components where edge defects are unacceptable. 2. Materials and Methods The GFRP sample used in this work measured 210 mm × 300 mm, with a thickness of 7.5 mm. The construction was 20 plies of 45°/135° biaxial glass fabric. The main thermo-physical properties are listed in Table 1 . Table 1 Thermo-mechanical properties of the fibre [ 20 ] and matrix [ 21 ] materials used Property Unit Fibre Matrix Name East Coast Fibreglass Biaxial E-Glass Hexion™ RIMR 135 & RIMH 137 Tensile Strength MPa 3,450–3,790 60–75 Tensile Modulus GPa 72.4 2.7–3.2 Density kg/m 3 2600 1190 Thermal Conductivity W/mK 1.2 0.2 Specific heat capacity J/kgK 800 900 Melting / Decomposition Temperature °C 1200 400 For laser cutting trials, a 5-axis Synova LCS 305 system was used, fitted with a 400 W nanosecond laser source (200 ns to 600 ns pulse duration) emitting at 532 nm (green) wavelength. The laser source consists of two individual resonators, each 200 W, operating at the same pulse frequency ( \(f\) ). The time offset between the two resonators (pulse delay, \({t}_{d}\) ) is specified by the operator, as shown in Fig. 2 . The operator also selects the pump current for each resonator (cf. laser power) along with the water pressure and shielding gas (Helium) flowrate. A series of 25 mm long cuts were made in the GFRP material, using a multi-pass, bi-directional scan strategy. The number of passes to achieve first penetration (breakthrough) and full cutting were recorded. The effective cutting speed ( \({v}_{Eff}\) ) was calculated by dividing the scan speed by the number of passes required to first penetrate the material. 3. Results and Discussion 3.1. Effect of Laser Power and Pulse Frequency The average laser power, pulse frequency, and pulse energy are all related and inter-dependent parameters ( \(average power=pulse energy \times frequency\) ). Thus, all present similar trends with respect to \({v}_{Eff}\) and wall edge taper. Figure 3 shows the results for pulse frequency. For all tests the average laser power was maintained at approximately 210 W. At low frequencies both \({v}_{Eff}\) and wall edge taper are high. This is due to the higher pulse energies and shorter pulse durations (7.15 mJ, 300 ns at 16 kHz) compared to high frequencies (2.59 mJ, 500 ns at 40 kHz). \({v}_{Eff}\) then reduces as frequency increases, to a minimum around 30 kHz, followed by a gradual increase with greater frequencies. The improved cutting rates at very high repetition frequencies are due to the laser pulses being closer in time (smaller pulse period) and thus there is reduced time for the material to cool. This greater thermal retention in turn minimizes the energy required to heat the material to the damage threshold temperature, maximizing the energy used to melt/ablate. The maximum repetition rate available on the Synova LCS 305 used is 40 kHz, and therefore further frequency increases were not possible. It should be noted that for the laser source used in this machine configuration (Photonics Industries DM2-532-200 (DH) [ 22 ]) the pulse width is dependent on the average power and pulse frequency. Thus, for the parameters used, the pulse duration ranged between 300 ns at 16 kHz to 500 ns at 40 kHz. 3.2. Effect of Scanning Speed Evaluations of the scanning speed were carried out using 18 kHz pulse frequency and 229 W laser power; the results are shown in Fig. 4 (a). The pulse duration and pulse energy were 345 ns and 6.4 mJ respectively. These results show that at 300 mm/min scan speed, the wall edge taper and \({v}_{Eff}\) are both minimized (0.81°, 7.5 mm/min). As the scan speed increases to 600 mm/min both the wall edge taper and \({v}_{Eff}\) reach their respective maxima (2.49°, 9.3 mm/min). This shows the conflicting requirements of productivity and cut quality common to many different machining operations, where improved cut quality necessitates a reduced productivity rate. However, further increasing the scan speed to 1200 mm/min, yields an improvement to the wall edge taper to 1.61°, while maintaining the high \({v}_{Eff}\) . Therefore, it may be preferable to increase the scanning speed further to maintain acceptable \({v}_{Eff}\) without sacrificing wall taper. Figure 4 (b) shows how the cut widths change with scan speed. From this it can be seen that the exit width decreases as the scan speed increases, while the entrance width is much larger than the exit for all scan speeds investigated. The enlarged entrance widths show there are cumulative thermal effects due to the many repeated passes required to cut the material. The lowest number of passes (40) was required at a scan speed of 300 mm/min, explaining why the entrance and exit widths were similar. However, the large kerf widths show the low scan speed is resulting in a higher thermal load than for higher scan speeds requiring more passes. At high scan speeds the entrance width is reduced (0.5 mm at 1200 mm/min) despite requiring 130 passes to cut. This shows that while the total energy input is higher, the scan speed is sufficient to not allow excessive heating at any location and thus minimizing the entrance width. 3.3. Effect of Pulse Delay Trials to evaluate the influence of pulse delay ( \({t}_{d}\) ) were conducted at 24 kHz pulse frequency, corresponding to a pulse period of 41.7 µs. The average power, pulse energies, and scan speed were constant at 227 W, 4.7 mJ, and 600 mm/min respectively. Figure 5 shows how \({v}_{Eff}\) changes with \({t}_{d}\) . No clear trend was seen between \({t}_{d}\) and other cut quality metrics. The minimum \({v}_{Eff}\) (4.1 mm/min) was found with a pulse delay of approximately 21 µs, effectively doubling the pulse frequency. Conversely, when the pulse delay is less than the pulse duration, sequential pulses can combine, either to effectively lengthen the pulse duration (M-shaped pulse) and/or increasing the pulse energy delivered before cooling can occur. While this may imply that to maximize cutting rate, \({t}_{d}\) ≈ 0 µs is ideal, in practice this is not shown by these results. Furthermore, the WJGL nozzle assembly is precision engineered, and thus even slight damage can harm the water jet integrity. Very high pulse energies are liable to result in such damage. The relatively low \({v}_{Eff}\) found at \({t}_{d}\) between 0.5 µs and 1.0 µs, likely due to the jet being disturbed by the previous pulse and insufficient time being available for it to stabilize again. Therefore, it is necessary to select a pulse delay that prevents the pulses from combining (i.e. \({t}_{d}\) ≥ pulse duration). The maximum \({v}_{Eff}\) found was at a \({t}_{d}\) of 5 µs (6.72 mm/min), highlighting the benefit of allowing time for the material to cool between successive laser pulses. 3.4. Qualitive Assessment of Cut Quality All cuts exhibited similar qualitative traits. These included discoloration/haze of the nearby matrix and edge chipping. Examples can be seen in Fig. 6 . There did not appear to be a strong correlation between any of these defects and WJGL parameters. This indicates that matrix haze and edge chipping are intrinsic to the WJGL process (at high average powers). Both arise due to the combined action of the applied laser energy and pressurized water jet allowing water ingress into the bulk material, possibly along the fibre-matrix interface, leading to the discoloration. Likewise, the edge chipping is a result of the matrix being burnt and removed by the laser, leaving exposed fibres, which are then in turn fractured by the action of the water jet. Another defect, also shown in Fig. 6 , is charring. This occurs due to the matrix being overheated by the laser and decomposing. The charring consistently appeared more significant as the number of repeated passes increased. This implies that at the laser powers used it is an inevitable side effect. It is known that at laser powers < 100 W the water jet is effective at completely cooling the material [ 23 ]. However, here the laser powers used were between 150 W and 230 W, and thus the water jet was insufficient to completely cool the material, leading to thermal damage. The charring occurred at all power levels used, but only after initial breakthrough was achieved. Charring was most severe where a large number of successive passes were required to finish cutting through the material. Figure 7 shows an example of this, with discolouration, charring, and fibre extrusion visible after the increased number of passes in Fig. 7 (b). This indicates that the charring is a cumulative effect, and relates to the water flow within the slot. Prior to breakthrough the only way for water to exit is via the cut entrance (top surface), while after breakthrough the water can drain through the cut base. Thus, it is likely that in blind machining (as with the incomplete slot) the water acts as a heatsink both as an incident jet, and while evacuating the cut, effectively doubling the heat removal capacity of the flow. 4. Conclusions The WJGL was used to successfully cut 7.5 mm thick GFRP. The number of passes required to achieve initial breakthrough of the full material thickness reveals interdependencies between the cutting efficiency and both the scan speed and pulse repetition frequency. Low pulse frequencies gave higher effective cutting speeds due to the higher pulse energies for a given laser power and enhanced cooling time between successive pulses. A scan speed of 600 mm/min gave the highest cutting rates, but increased wall edge taper, thus a compromise is required between speed and quality during WJGL cutting of GFRP. The effective cutting speed to achieve a full cut is strongly related to pulse delay, showing a twin pulse delivery method is preferable to an effective higher repetition frequency for maximizing productivity. The results show, for GFRP, the pulse delay can be set between 2.5 µs and 7.5 µs for the highest cutting rates. Various defects were observed on all cuts irrespective of WJGL parameters used. Material haze and edge chipping are unavoidable due to the combined action of the applied heat and pressurized water jet. Charring of the cut surface was also observed, mostly correlating to number of passes required. Charring can be minimized by reducing the number of additional passes required to fully cut after initial penetration, due to the additional cooling capacity afforded by water exiting the cut from the top surface rather than draining through the base. Declarations This research was Co-funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. Agreement No 101096425 - EoLO-HUBs - HORIZON-CL5-2022-D3-01. Additional funding has been provided by Innovate UK though their Horizon Europe Guarantee Fund (grant number 10066018) and UKRI Future Leaders Fellowship under grant number MR/V02180X/1. Materials used were provided by the National Composite Centre (Bristol, UK) for use in this research. The authors have no relevant financial or non-financial interests to disclose. References Abdur Rob S, Srivastava A (2022) Turning of Carbon Fiber Reinforced Polymer (CFRP) Composites: Process Modelling and Optimization using Taguchi Analysis and Multi-Objective Genetic Algorithm. Manuf Lett no 33:29–40 Xu J, Geier N, Shen J, Krishnaraj V, Samsudeensadham S (2023) A Review on CFRP Drilling: Fundamental Mechanisms, Damage Issues, and Approaches Towards High-Quality Drilling. J Mater Res Technol no. 24:9677–9707 El-Hofy M, Helmy M, Escobar-Palafox G, Kerrigan K, Scaife R, El-Hofy H (2018) Abrasive Water Jet Machining of Multidirectional CFRP Laminates, in Procedia CIRP , Bilbao, Spain Hussien AA, Qasem I, Kataraki PS, Al-Kouz W, Janvekar AA (2021) Studying the Performance of Cutting Carbon Fibre-Reinforced Plastic Using an Abrasive Water Jet Technique. J Mech Eng 4(67):135–141 Abdallah R, Soo S, Hood R (2018) A feasibility study on wire electrical discharge machining of carbon fibre reinforced plastic composites, in 8th CIRP Conference on High Performance Cutting (HPC 2018) , Budapest, Hungary Shyha I (2013) An Investigation into CO2 Laser Trimming of CFRP and GFRP Composites, in Procedia Engineering , Zaragoza, Spain Tabar M, Hashemzadeh M, Rejani A (2023) CO2 laser cutting of reinforced polyester (CGFRP and GFRP) sheets: An experimental investigation into specific point energy, cutting volume efficiency and material removal rate (MRR). J Manuf Process 97:137–147 Huang S, Fu Z, Liu C, Wang C (2021) Interactional Relations Between Ablation and Heat Affected Zone (HAZ) in Laser Cutting of Glass Fiber Reinforced Polymer (GFRP) Composite By Fiber Laser. Opt Laser Technol no 158 Leone C, Mingione E, Genna S (2021) Laser Cutting of CFRP by Quasi-Continuous Wave (QCW) Fibre Laser: Effect of Process Parameters and Analysis of the HAZ Index. Compos Part B, 224 Li M, Li S, Yang X, Zhang Y, Liang Z (2018) Study on Fibre Laser Machining Quality of Plain Woven CFRP Laminates. Appl Phys A, 127 Riveiro A, Quintero F, Lusquiños F, del Val J, Comesaña R, Boutinguiza M, Pou J (2017) Laser Cutting of Carbon Fiber Composite Materials. in Procedia Manufacturing. Vigo (Pontevedra), Spain Spiegel A, Vago N, Wagner FR (2004) High efficiency Raman scattering in micrometer-sized water jets. Opt Eng 43(2):450–454 Wagner F, Sibailly O, Vágó N, Romanowicz R, Richerzhagen B (2003) The Laser Microjet® Technology – 10 Years of Development, in International Congress on Laser Materials Processing and Laser Microfabrication , Orlando, USA Adelmann B, Ngo C, Hellmann R (2015) High aspect ratio cutting of metals using water jet guided laser. Int J Adv Manuf Technol no. 80:2053–2060 Sun D, Han F, Ying W, Jin C (2018) Surface Integrity of Water Jet Guided Laser Machining of CFRP, in Procedia CIRP , Tianjin, China Synova SA The Laser MicroJet® Technology, [Online]. Available: https://www.synova.ch/technology/synova-laser-microjet.html Wu Y, Zhang G, Wang J, Chao Y, Zhang W (2021) The Cutting Process and Damage Mechanism of Large Thickness CFRP Based on Water Jet Guided Laser Processing. Opt Laser Technol no 141 Sun D, Han F, Ying W (2019) The Experimental Investigation of Water Jet-Guided Laser Cutting of CFRP. Int J Adv Manuf Technol no. 102:719–729 Elkington H, Diboine J, Chingwena K, Mason B, Marimuthu S (2024) Water jet guided nanosecond laser cutting of CFRP. Opt Laser Technol, 171 Fibreglass EC Technical data Sheet 62014, 28 January 2020. [Online]. Available: https://www.ecfibreglasssupplies.co.uk/user/TechnicalDataSheet/506.pdf . [Accessed 30 November 2023] Hexion, Technical Data Sheet: EPIKOTE Resin MGS RIMR 135 and, Curing Agent EPIKURE (2006) MGS RIMH 134–RIMH 137, [Online]. Available: https://www.metyx.com/wp-content/uploads/PDF_Files/Hexion/TDS/TDS%20RIMH%20137.pdf . [Accessed 30 November 2023] DM Photonics Industries International Inc., Dual Head Series (2024) [Online]. Available: https://www.photonix.com/product/dm-dual-head-green-series/ . [Accessed March 2024] Heilmann E-M, Seidl A, Hellman R (2011) Water Jet Guided Laser Cutting of Silicon Thin Films using 515 nm Disk Laser. J Laser Micro/Nanoeng 2(6):168–173 Cite Share Download PDF Status: Posted Version 1 posted 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. 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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-4630208","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":318952061,"identity":"d8e6675e-49f9-49ae-8792-5fa1e0cb3154","order_by":0,"name":"Ben Mason","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA9klEQVRIiWNgGAWjYBACeyBm5gGx2BvYiNNi2ADUMgfE4jkM1iJBUIvBAaCWP2C1yURqMWzvPcCcU1MnZy75/tiDDwzb6vgbmI99/IJHiz3PuQTmnGOHjS1nJ7MbzmC4LSFxgC15tgw+W2bkGDDnsB1I3HA7mU2a999tCQMGHmNmfM4zuP/GgJnnX13ihpuH2aT/MBCj5QaPATNvG3PihhvMbNIMUC2MH/A5rCfH4DBv32FjgzPJZpI9DLclZxxmS2bGo4PBnv2M4WOeb3VyBscPPpP4wXCbn7+9+TDjD3x6gOAAKpcZlh5IAgRtGQWjYBSMghEFAPZJRnNDCuouAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-2136-3252","institution":"The Manufacturing Technology Centre Limited","correspondingAuthor":true,"prefix":"","firstName":"Ben","middleName":"","lastName":"Mason","suffix":""},{"id":318952062,"identity":"c9843ccb-0fd6-4f81-bb67-5dcb7a198eae","order_by":1,"name":"Helen Elkington","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Helen","middleName":"","lastName":"Elkington","suffix":""},{"id":318952063,"identity":"118813b6-4547-40cb-9d4d-449cfdf35d83","order_by":2,"name":"Kursad Sezer","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Kursad","middleName":"","lastName":"Sezer","suffix":""},{"id":318952064,"identity":"6c09d580-8060-45c2-98eb-95429d2fe67b","order_by":3,"name":"Sundar Marimuthu","email":"","orcid":"","institution":"","correspondingAuthor":false,"prefix":"","firstName":"Sundar","middleName":"","lastName":"Marimuthu","suffix":""}],"badges":[],"createdAt":"2024-06-24 12:31:43","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4630208/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4630208/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":60484333,"identity":"347e3401-e21f-4ea7-be59-6d58f2ba540b","added_by":"auto","created_at":"2024-07-17 09:14:23","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":306447,"visible":true,"origin":"","legend":"\u003cp\u003eSchematic of the water jet guided laser principle [16]\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/37d59df544a1038872bf6ac8.png"},{"id":60483381,"identity":"e30190ba-af21-4e14-a2d6-032eb784c10f","added_by":"auto","created_at":"2024-07-17 09:06:23","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":241252,"visible":true,"origin":"","legend":"\u003cp\u003eTwin pulse delivery shown as; (a) a schematic, and (b) oscilloscope measurements with different t\u003csub\u003ed\u003c/sub\u003e values\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/1f92b8cce57f5feff1adc323.png"},{"id":60483386,"identity":"2ce5f307-cc34-4f07-b8ba-d48fe2269789","added_by":"auto","created_at":"2024-07-17 09:06:24","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":138216,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of pulse repetition frequency on vEff and wall edge taper\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/8872bee601a50870f321b007.png"},{"id":60485234,"identity":"78e0f058-54ec-4894-8638-7aea60c11365","added_by":"auto","created_at":"2024-07-17 09:22:23","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":232909,"visible":true,"origin":"","legend":"\u003cp\u003ePlot of scanning speed against (a) vEff and wall edge taper, and (b) cut width\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/c2e5e66f6623ba1dc55ffa39.png"},{"id":60483387,"identity":"678050b9-8644-40dc-9d2e-b49a45c5ba66","added_by":"auto","created_at":"2024-07-17 09:06:24","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":102308,"visible":true,"origin":"","legend":"\u003cp\u003eEffect of pulse delay on vEff\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/3d164aedb99041e2d4fe8cf7.png"},{"id":60483383,"identity":"42631cca-b3f3-4e77-a02c-20c49272de6d","added_by":"auto","created_at":"2024-07-17 09:06:23","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":970098,"visible":true,"origin":"","legend":"\u003cp\u003eExamples of different damage types observed\u003c/p\u003e","description":"","filename":"floatimage6.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/5eb9e473e2e57d9dce118edb.png"},{"id":60483385,"identity":"fd8a9118-0644-4973-836d-1a1f4629bf43","added_by":"auto","created_at":"2024-07-17 09:06:23","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":630490,"visible":true,"origin":"","legend":"\u003cp\u003eImages showing cut entrance after (a) 153 passes, and (b) 223 passes\u003c/p\u003e","description":"","filename":"floatimage7.png","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/426126a1c26af1819f1144e4.png"},{"id":61604881,"identity":"4d93ebbf-0968-47ea-841f-038a5e75f826","added_by":"auto","created_at":"2024-08-01 20:27:09","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4587184,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4630208/v1/1e501bf3-8a37-4679-af9a-b2e1fe778f7f.pdf"}],"financialInterests":"","formattedTitle":"Water Jet Guided Laser Cutting of Thick Section Glass Fibre Reinforced Polymer","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eGlass fibre reinforced polymer (GFRP) is an attractive material due to its higher specific strength and stiffness than metals, and significantly reduced cost compared to carbon fibre reinforced polymer (CFRP). It is commonly used in many engineered structures, from wind turbines to sportscars and watercraft. However, like all fibre reinforced polymer composites, while the manufacturing is nearly net-shape, there are still certain machining operations required to achieve the desired shape. Traditional machining (drilling, milling, etc.) suffer from accelerated tool wear [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] and can lead to material damage such as delamination and edge chipping [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Therefore, non-conventional cutting methods have gained much attention in recent years. Abrasive water jet (AWJ) has been investigated for cutting CFRP, with most researchers finding strong links between the fibre orientation [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] and jet pressure [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e] with the achievable cut quality. Wire electro-discharge machining (W-EDM) is another candidate for cutting CFRP [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e], however is unsuitable for GFRP due to the materials electrical insulating properties. There has been comparatively little interest in cutting of GFRP using such nonconventional techniques.\u003c/p\u003e \u003cp\u003eLaser cutting has been extensively researched for cutting CFRP, and to a lesser extent GFRP, as it addresses the problems of the previously mentioned technologies. Specifically, no tool wear, negligible force applied to the material, and a reduced risk of material damage. Shyha [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] found a higher material removal rate (MRR) for laser cutting of GFRP than CFRP, but with a more complex relationship to scan speed. It has been repeatedly found that when laser cutting GFRP, the cutting efficiency shows nonlinear relationships with both laminate thickness [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] and laser power [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e], complicating process optimization.\u003c/p\u003e \u003cp\u003eFurther insight is offered by the research into laser cutting of CFRP. For example, shorter pulse durations are preferable for minimizing the heat affected zone (HAZ) [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] and while higher average power enables faster cutting speeds and thus reduced HAZ, it increases the risk of bridging (small regions of uncut material at the cut exit) [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Therefore, it is clear that a processing window exists where full cuts can be achieved with an acceptable HAZ to reach a target cutting speed. It has also been suggested that different laminate constructions (in terms of fibre orientation, matrix material, fibre content, etc.) may require bespoke optimizations [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe water jet guided laser (WJGL) technology uses a narrow, laminar jet of water to guide the laser beam to the workpiece. The concept is shown diagrammatically in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. The water does not contribute directly to the cutting action, only to maintain a consistent beam width [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e] (no divergence) and to cool the cut material [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Therefore, the resulting long, narrow, cylindrical beam enables thick section cutting of various materials [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] with minimal HAZ [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. An added effect is the continuous water flow effectively evacuates molten material and other debris, preventing spatter [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThere is no current literature regarding WJGL cutting of GFRP, with more effort focused on cutting CFRP. For example, Sun et al. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] used a 10 W nanosecond UV laser to cut 1 mm thick (5 ply) CFRP with both WJGL and conventional lasers. They found WJGL to be approximately 50 \u0026times; slower than the conventional laser, in part due to attenuation within the water jet and the larger effective spot size (10 \u0026times;). Wu et al. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] used a 60 W nanosecond green WJGL to cut 1 mm thick CFRP, achieving a relatively high effective cutting speed of 75 mm/min. While processing thicker sections, the use of parallel scanning was required to ensure jet integrity. There is little information regarding high-power WJGL cutting of CFRP, with one such example from Sun et al. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] who used a 350 W microsecond source for cutting 0.5 mm thick (4 ply) CFRP, finding different scanning strategies (e.g. parallel paths) could greatly improve the cut surface quality at the expense of processing speed. Finally, Elkington et al. [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e] evaluated the influence of various process parameters (laser power, pulse frequency, and jet pressure) on cut speed and wall taper, using a green nanosecond source, operating at between 130 W and 270 W.\u003c/p\u003e \u003cp\u003eOverall, WJGL cutting of CFRP has shown to have reduced productivity compared to alternative techniques, but with improved cut quality. It is likely that with higher power lasers, maximum cutting rates and thicknesses will only increase, potentially making WJGL cutting a compelling option for processing very thick composites, such as GFRP, or processing components where edge defects are unacceptable.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cp\u003eThe GFRP sample used in this work measured 210 mm \u0026times; 300 mm, with a thickness of 7.5 mm. The construction was 20 plies of 45\u0026deg;/135\u0026deg; biaxial glass fabric. The main thermo-physical properties are listed in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\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\u003eThermo-mechanical properties of the fibre [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e] and matrix [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] materials used\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\u003eProperty\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eUnit\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eFibre\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMatrix\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eName\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEast Coast Fibreglass Biaxial E-Glass\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003eHexion\u0026trade;\u003c/p\u003e \u003cp\u003eRIMR 135 \u0026amp; RIMH 137\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTensile Strength\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMPa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e3,450\u0026ndash;3,790\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e60\u0026ndash;75\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eTensile Modulus\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eGPa\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e72.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e2.7\u0026ndash;3.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDensity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ekg/m\u003csup\u003e3\u003c/sup\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e2600\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e1190\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eThermal Conductivity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eW/mK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSpecific heat capacity\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eJ/kgK\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e800\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e900\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eMelting / Decomposition Temperature\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u0026deg;C\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e1200\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e400\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\u003eFor laser cutting trials, a 5-axis Synova LCS 305 system was used, fitted with a 400 W nanosecond laser source (200 ns to 600 ns pulse duration) emitting at 532 nm (green) wavelength. The laser source consists of two individual resonators, each 200 W, operating at the same pulse frequency (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(f\\)\u003c/span\u003e\u003c/span\u003e). The time offset between the two resonators (pulse delay, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e) is specified by the operator, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The operator also selects the pump current for each resonator (cf. laser power) along with the water pressure and shielding gas (Helium) flowrate.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eA series of 25 mm long cuts were made in the GFRP material, using a multi-pass, bi-directional scan strategy. The number of passes to achieve first penetration (breakthrough) and full cutting were recorded. The effective cutting speed (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e) was calculated by dividing the scan speed by the number of passes required to first penetrate the material.\u003c/p\u003e"},{"header":"3. Results and Discussion","content":"\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Effect of Laser Power and Pulse Frequency\u003c/h2\u003e \u003cp\u003eThe average laser power, pulse frequency, and pulse energy are all related and inter-dependent parameters (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(average power=pulse energy \\times frequency\\)\u003c/span\u003e\u003c/span\u003e). Thus, all present similar trends with respect to \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e and wall edge taper. Figure\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e shows the results for pulse frequency. For all tests the average laser power was maintained at approximately 210 W. At low frequencies both \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e and wall edge taper are high. This is due to the higher pulse energies and shorter pulse durations (7.15 mJ, 300 ns at 16 kHz) compared to high frequencies (2.59 mJ, 500 ns at 40 kHz). \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e then reduces as frequency increases, to a minimum around 30 kHz, followed by a gradual increase with greater frequencies. The improved cutting rates at very high repetition frequencies are due to the laser pulses being closer in time (smaller pulse period) and thus there is reduced time for the material to cool. This greater thermal retention in turn minimizes the energy required to heat the material to the damage threshold temperature, maximizing the energy used to melt/ablate. The maximum repetition rate available on the Synova LCS 305 used is 40 kHz, and therefore further frequency increases were not possible.\u003c/p\u003e \u003cp\u003eIt should be noted that for the laser source used in this machine configuration (Photonics Industries DM2-532-200 (DH) [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]) the pulse width is dependent on the average power and pulse frequency. Thus, for the parameters used, the pulse duration ranged between 300 ns at 16 kHz to 500 ns at 40 kHz.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Effect of Scanning Speed\u003c/h2\u003e \u003cp\u003eEvaluations of the scanning speed were carried out using 18 kHz pulse frequency and 229 W laser power; the results are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a). The pulse duration and pulse energy were 345 ns and 6.4 mJ respectively. These results show that at 300 mm/min scan speed, the wall edge taper and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e are both minimized (0.81\u0026deg;, 7.5 mm/min). As the scan speed increases to 600 mm/min both the wall edge taper and \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e reach their respective maxima (2.49\u0026deg;, 9.3 mm/min). This shows the conflicting requirements of productivity and cut quality common to many different machining operations, where improved cut quality necessitates a reduced productivity rate. However, further increasing the scan speed to 1200 mm/min, yields an improvement to the wall edge taper to 1.61\u0026deg;, while maintaining the high \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e. Therefore, it may be preferable to increase the scanning speed further to maintain acceptable \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e without sacrificing wall taper.\u003c/p\u003e \u003cp\u003eFigure \u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e (b) shows how the cut widths change with scan speed. From this it can be seen that the exit width decreases as the scan speed increases, while the entrance width is much larger than the exit for all scan speeds investigated. The enlarged entrance widths show there are cumulative thermal effects due to the many repeated passes required to cut the material. The lowest number of passes (40) was required at a scan speed of 300 mm/min, explaining why the entrance and exit widths were similar. However, the large kerf widths show the low scan speed is resulting in a higher thermal load than for higher scan speeds requiring more passes. At high scan speeds the entrance width is reduced (0.5 mm at 1200 mm/min) despite requiring 130 passes to cut. This shows that while the total energy input is higher, the scan speed is sufficient to not allow excessive heating at any location and thus minimizing the entrance width.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Effect of Pulse Delay\u003c/h2\u003e \u003cp\u003eTrials to evaluate the influence of pulse delay (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e) were conducted at 24 kHz pulse frequency, corresponding to a pulse period of 41.7 \u0026micro;s. The average power, pulse energies, and scan speed were constant at 227 W, 4.7 mJ, and 600 mm/min respectively. Figure\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e shows how \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e changes with \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e. No clear trend was seen between \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e and other cut quality metrics. The minimum \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e (4.1 mm/min) was found with a pulse delay of approximately 21 \u0026micro;s, effectively doubling the pulse frequency. Conversely, when the pulse delay is less than the pulse duration, sequential pulses can combine, either to effectively lengthen the pulse duration (M-shaped pulse) and/or increasing the pulse energy delivered before cooling can occur. While this may imply that to maximize cutting rate, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e \u0026asymp; 0 \u0026micro;s is ideal, in practice this is not shown by these results. Furthermore, the WJGL nozzle assembly is precision engineered, and thus even slight damage can harm the water jet integrity. Very high pulse energies are liable to result in such damage. The relatively low \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e found at \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e between 0.5 \u0026micro;s and 1.0 \u0026micro;s, likely due to the jet being disturbed by the previous pulse and insufficient time being available for it to stabilize again. Therefore, it is necessary to select a pulse delay that prevents the pulses from combining (i.e. \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e\u0026ge; pulse duration). The maximum \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({v}_{Eff}\\)\u003c/span\u003e\u003c/span\u003e found was at a \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({t}_{d}\\)\u003c/span\u003e\u003c/span\u003e of 5 \u0026micro;s (6.72 mm/min), highlighting the benefit of allowing time for the material to cool between successive laser pulses.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e3.4. Qualitive Assessment of Cut Quality\u003c/h2\u003e \u003cp\u003eAll cuts exhibited similar qualitative traits. These included discoloration/haze of the nearby matrix and edge chipping. Examples can be seen in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e. There did not appear to be a strong correlation between any of these defects and WJGL parameters. This indicates that matrix haze and edge chipping are intrinsic to the WJGL process (at high average powers). Both arise due to the combined action of the applied laser energy and pressurized water jet allowing water ingress into the bulk material, possibly along the fibre-matrix interface, leading to the discoloration. Likewise, the edge chipping is a result of the matrix being burnt and removed by the laser, leaving exposed fibres, which are then in turn fractured by the action of the water jet.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAnother defect, also shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e, is charring. This occurs due to the matrix being overheated by the laser and decomposing. The charring consistently appeared more significant as the number of repeated passes increased. This implies that at the laser powers used it is an inevitable side effect. It is known that at laser powers\u0026thinsp;\u0026lt;\u0026thinsp;100 W the water jet is effective at completely cooling the material [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. However, here the laser powers used were between 150 W and 230 W, and thus the water jet was insufficient to completely cool the material, leading to thermal damage. The charring occurred at all power levels used, but only after initial breakthrough was achieved. Charring was most severe where a large number of successive passes were required to finish cutting through the material. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e shows an example of this, with discolouration, charring, and fibre extrusion visible after the increased number of passes in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e (b). This indicates that the charring is a cumulative effect, and relates to the water flow within the slot. Prior to breakthrough the only way for water to exit is via the cut entrance (top surface), while after breakthrough the water can drain through the cut base. Thus, it is likely that in blind machining (as with the incomplete slot) the water acts as a heatsink both as an incident jet, and while evacuating the cut, effectively doubling the heat removal capacity of the flow.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Conclusions","content":"\u003cp\u003eThe WJGL was used to successfully cut 7.5 mm thick GFRP. The number of passes required to achieve initial breakthrough of the full material thickness reveals interdependencies between the cutting efficiency and both the scan speed and pulse repetition frequency. Low pulse frequencies gave higher effective cutting speeds due to the higher pulse energies for a given laser power and enhanced cooling time between successive pulses. A scan speed of 600 mm/min gave the highest cutting rates, but increased wall edge taper, thus a compromise is required between speed and quality during WJGL cutting of GFRP.\u003c/p\u003e \u003cp\u003eThe effective cutting speed to achieve a full cut is strongly related to pulse delay, showing a twin pulse delivery method is preferable to an effective higher repetition frequency for maximizing productivity. The results show, for GFRP, the pulse delay can be set between 2.5 \u0026micro;s and 7.5 \u0026micro;s for the highest cutting rates.\u003c/p\u003e \u003cp\u003eVarious defects were observed on all cuts irrespective of WJGL parameters used. Material haze and edge chipping are unavoidable due to the combined action of the applied heat and pressurized water jet. Charring of the cut surface was also observed, mostly correlating to number of passes required. Charring can be minimized by reducing the number of additional passes required to fully cut after initial penetration, due to the additional cooling capacity afforded by water exiting the cut from the top surface rather than draining through the base.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eThis research was Co-funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or CINEA. Neither the European Union nor the granting authority can be held responsible for them. Agreement No 101096425 - EoLO-HUBs - HORIZON-CL5-2022-D3-01. Additional funding has been provided by Innovate UK though their Horizon Europe Guarantee Fund (grant number 10066018) and UKRI Future Leaders Fellowship under grant number MR/V02180X/1. Materials used were provided by the National Composite Centre (Bristol, UK) for use in this research.\u003c/p\u003e \u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbdur Rob S, Srivastava A (2022) Turning of Carbon Fiber Reinforced Polymer (CFRP) Composites: Process Modelling and Optimization using Taguchi Analysis and Multi-Objective Genetic Algorithm. Manuf Lett no 33:29\u0026ndash;40\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eXu J, Geier N, Shen J, Krishnaraj V, Samsudeensadham S (2023) A Review on CFRP Drilling: Fundamental Mechanisms, Damage Issues, and Approaches Towards High-Quality Drilling. J Mater Res Technol no. 24:9677\u0026ndash;9707\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eEl-Hofy M, Helmy M, Escobar-Palafox G, Kerrigan K, Scaife R, El-Hofy H (2018) Abrasive Water Jet Machining of Multidirectional CFRP Laminates, in \u003cem\u003eProcedia CIRP\u003c/em\u003e, Bilbao, Spain\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHussien AA, Qasem I, Kataraki PS, Al-Kouz W, Janvekar AA (2021) Studying the Performance of Cutting Carbon Fibre-Reinforced Plastic Using an Abrasive Water Jet Technique. J Mech Eng 4(67):135\u0026ndash;141\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAbdallah R, Soo S, Hood R (2018) A feasibility study on wire electrical discharge machining of carbon fibre reinforced plastic composites, in \u003cem\u003e8th CIRP Conference on High Performance Cutting (HPC 2018)\u003c/em\u003e, Budapest, Hungary\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShyha I (2013) An Investigation into CO2 Laser Trimming of CFRP and GFRP Composites, in \u003cem\u003eProcedia Engineering\u003c/em\u003e, Zaragoza, Spain\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTabar M, Hashemzadeh M, Rejani A (2023) CO2 laser cutting of reinforced polyester (CGFRP and GFRP) sheets: An experimental investigation into specific point energy, cutting volume efficiency and material removal rate (MRR). J Manuf Process 97:137\u0026ndash;147\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHuang S, Fu Z, Liu C, Wang C (2021) Interactional Relations Between Ablation and Heat Affected Zone (HAZ) in Laser Cutting of Glass Fiber Reinforced Polymer (GFRP) Composite By Fiber Laser. Opt Laser Technol no 158\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLeone C, Mingione E, Genna S (2021) Laser Cutting of CFRP by Quasi-Continuous Wave (QCW) Fibre Laser: Effect of Process Parameters and Analysis of the HAZ Index. Compos Part B, 224\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLi M, Li S, Yang X, Zhang Y, Liang Z (2018) Study on Fibre Laser Machining Quality of Plain Woven CFRP Laminates. Appl Phys A, 127\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRiveiro A, Quintero F, Lusqui\u0026ntilde;os F, del Val J, Comesa\u0026ntilde;a R, Boutinguiza M, Pou J (2017) Laser Cutting of Carbon Fiber Composite Materials. in Procedia Manufacturing. Vigo (Pontevedra), Spain\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSpiegel A, Vago N, Wagner FR (2004) High efficiency Raman scattering in micrometer-sized water jets. Opt Eng 43(2):450\u0026ndash;454\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWagner F, Sibailly O, V\u0026aacute;g\u0026oacute; N, Romanowicz R, Richerzhagen B (2003) The Laser Microjet\u0026reg; Technology \u0026ndash; 10 Years of Development, in \u003cem\u003eInternational Congress on Laser Materials Processing and Laser Microfabrication\u003c/em\u003e, Orlando, USA\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAdelmann B, Ngo C, Hellmann R (2015) High aspect ratio cutting of metals using water jet guided laser. Int J Adv Manuf Technol no. 80:2053\u0026ndash;2060\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun D, Han F, Ying W, Jin C (2018) Surface Integrity of Water Jet Guided Laser Machining of CFRP, in \u003cem\u003eProcedia CIRP\u003c/em\u003e, Tianjin, China\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSynova SA The Laser MicroJet\u0026reg; Technology, [Online]. Available: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.synova.ch/technology/synova-laser-microjet.html\u003c/span\u003e\u003cspan address=\"https://www.synova.ch/technology/synova-laser-microjet.html\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWu Y, Zhang G, Wang J, Chao Y, Zhang W (2021) The Cutting Process and Damage Mechanism of Large Thickness CFRP Based on Water Jet Guided Laser Processing. Opt Laser Technol no 141\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSun D, Han F, Ying W (2019) The Experimental Investigation of Water Jet-Guided Laser Cutting of CFRP. Int J Adv Manuf Technol no. 102:719\u0026ndash;729\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eElkington H, Diboine J, Chingwena K, Mason B, Marimuthu S (2024) Water jet guided nanosecond laser cutting of CFRP. Opt Laser Technol, 171\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFibreglass EC Technical data Sheet 62014, 28 January 2020. [Online]. Available: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.ecfibreglasssupplies.co.uk/user/TechnicalDataSheet/506.pdf\u003c/span\u003e\u003cspan address=\"https://www.ecfibreglasssupplies.co.uk/user/TechnicalDataSheet/506.pdf\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. [Accessed 30 November 2023]\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHexion, Technical Data Sheet: EPIKOTE Resin MGS RIMR 135 and, Curing Agent EPIKURE (2006) MGS RIMH 134\u0026ndash;RIMH 137, [Online]. Available: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.metyx.com/wp-content/uploads/PDF_Files/Hexion/TDS/TDS%20RIMH%20137.pdf\u003c/span\u003e\u003cspan address=\"https://www.metyx.com/wp-content/uploads/PDF_Files/Hexion/TDS/TDS%20RIMH%20137.pdf\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. [Accessed 30 November 2023]\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDM Photonics Industries International Inc., Dual Head Series (2024) [Online]. Available: \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://www.photonix.com/product/dm-dual-head-green-series/\u003c/span\u003e\u003cspan address=\"https://www.photonix.com/product/dm-dual-head-green-series/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e. [Accessed March 2024]\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHeilmann E-M, Seidl A, Hellman R (2011) Water Jet Guided Laser Cutting of Silicon Thin Films using 515 nm Disk Laser. J Laser Micro/Nanoeng 2(6):168\u0026ndash;173\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Water Jet Guided Laser, Glass Fibre Reinforced Polymer, Laser Cutting, Thick Section Cutting","lastPublishedDoi":"10.21203/rs.3.rs-4630208/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4630208/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eLaser cutting is well established for cutting metals, alloys, and ceramics. However, its application for cutting fibre reinforced polymer composites is constrained due to specific challenges. The distinct optical and thermal properties of the fibres and matrix often lead to excessive thermal damage. Thick-section laser cutting of composites is an especially challenging task. The water jet guided laser (WJGL), employing a hair-thin water jet to guide the laser, has proven successful for such challenging materials. Thermal damage is minimized by effective in-situ cooling of the interaction zone by the water flow.\u003c/p\u003e \u003cp\u003eThis work evaluates the feasibility of WJGL cutting glass fiber reinforced polymer (GFRP). A WJGL system, fitted with a 400 W green nanosecond laser, was used to cut 7.5 mm thick GFRP using a multi-pass strategy. Effective cutting speeds of up to 10.1 mm/min were obtained with an average wall taper of 1.91\u0026deg;. Improvements in taper angle were realised via reduced effective cutting speeds (0.81\u0026deg;, 7.5 mm/min). Defects including charring, edge chipping, and matrix discolouration were observed. These results show that while the WJGL can cut thick GFRP with minimal defects, further work is required to enhance the productivity before the technique could be viable for widespread adoption.\u003c/p\u003e","manuscriptTitle":"Water Jet Guided Laser Cutting of Thick Section Glass Fibre Reinforced Polymer","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-07-17 09:06:19","doi":"10.21203/rs.3.rs-4630208/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"9f2eb922-89a7-4d3f-8d00-bd38aa41a94b","owner":[],"postedDate":"July 17th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-08-01T20:19:00+00:00","versionOfRecord":[],"versionCreatedAt":"2024-07-17 09:06:19","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4630208","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4630208","identity":"rs-4630208","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}