Title: Robust Out-of-Autoclave Prepreg Processing Using a Semi-Permeable Membrane to Maintain Resin Pressure
Authors: Daniel Zebrine, Mark Anders, Steven Nutt
Abstract: Out-of-autoclave processing of carbon fiber-reinforced polymer composites offers certain advantages compared to autoclave cure, but limited compaction pressure often causes inconsistent part quality. To aid in removing entrapped air, OoA prepregs can be semi-impregnated to leave dry fiber tows and increase in-plane or through-thickness air evacuation. Porosity due to volatile evolution can arise if resin pressure decreases during the cure cycle, which can occur when resin bleeds out of the laminate. In this work, we investigate the use of a discontinuous resin film combined with a semi-permeable (air-permeable, resin-impermeable) release film to allow through-thickness air evacuation while simultaneously restricting resin loss. In situ measurements of resin pressure were deployed to test the hypothesis that resin pressure was maintained during cure when using a semi-permeable release film. Concurrently, visualization of the tool-side surface during cure revealed efficient evacuation of entrapped air. Porosity in laminates formed at high temperatures when using resin-permeable consumables, but did not form when using resin-impermeable (semi-permeable) consumables. To confirm that the observed void growth behavior was due to a loss in resin pressure, experiments were conducted to measure resin pressure during cure with both resin-permeable and resin-impermeable (semi-permeable) consumables. In both cases, resin pressure peaked before decreasing, a finding attributed to resin flowing to fill dry regions in the fabric, present by design. The drop in resin pressure, however, was greater in magnitude and longer in duration when using resin-permeable boundaries, indicating that the observed void growth at elevated temperature was caused by a loss in resin pressure. Use of a semi-permeable membrane was effective in retaining resin content and mitigating such porosity.
References: ] Campbell FC, Mallow AR, Browning CE. Porosity in carbon fiber composites an overview of causes. J Adv Mater 1995;26:18–33.  Campbell FC. Manufacturing Technology for Aerospace Structural Materials. London: Elsevier; 2006.  Repecka L, Boyd J. Vacuum-bag-only-curable prepregs that produce void-free parts. Int SAMPE Symp Exhib 2002;47 II:1862–74.  Xu GF, Repecka L, Mortimer S, Peake S, Boyd J. Manufacture of Void-free Laminates and Use Thereof, 2002.  Bond GG, Griffith JM, Hahn GL, Bongiovanni C, Boyd J. Non-autoclave prepreg manufacturing technology. Int SAMPE Tech Conf 2008.  Hartness JT, Xu GF. Resin Composition, A Fiber Reinforced Material Having a Partially Impregnated Resin and Composites Made Therefrom, 2000.  Centea T, Grunenfelder LK, Nutt SR. A review of out-of-autoclave prepregs - Material properties, process phenomena, and manufacturing considerations. Compos Part A Appl Sci Manuf 2015;70:132–54. doi:10.1016/j.compositesa.2014.09.029.  Louis BM, Hsiao K, Fernlund G. Gas permeability measurements of out of autoclave prepreg MTM45-1/CF2426A. Int SAMPE Symp Exhib 2010.  Farhang L, Fernlund G. Out-of-Autoclave Prepreg Laminates. 18Th Int Conf Compos Mater 2011.  Arafath ARA, Fernlund G, Poursartip A. Gas transport in prepregs: Model and permeability experiments. ICCM Int Conf Compos Mater 2009.  Kay J, Fernlund G. Processing conditions and voids in out of autoclave prepregs. Int SAMPE Tech Conf 2012.  Hamill L, Centea T, Nutt S. Surface porosity during vacuum bag-only prepreg processing: Causes and mitigation strategies. Compos Part A Appl Sci Manuf 2015;75:1–10. doi:10.1016/j.compositesa.2015.04.009.  Juska TD, Musser BS, Jordan BP, Hall JC. The new infusion: Oven vacuum bag prepreg fabrication. Int SAMPE Symp Exhib 2009;54.  Centea T, Hughes SM, Payette S, Kratz J, Hubert P. Scaling challenges encountered with out-of-autoclave prepregs. 53rd AIAA/ASME/ASCE/AHS/ASC Struct Struct Dyn Mater Conf 2012 2012:1–15. doi:10.2514/6.2012-1568.  Tavares SS, Caillet-Bois N, Michaud V, Månson J-AE. Vacuum-bag processing of sandwich structures: Role of honeycomb pressure level on skin–core adhesion and skin quality. Compos Sci Technol 2010;70:797–803. doi:10.1016/j.compscitech.2010.01.015.  Grunenfelder LK, Dills A, Centea T, Nutt S. Effect of prepreg format on defect control in out-of-autoclave processing. Compos Part A Appl Sci Manuf 2017;93:88–99. doi:10.1016/j.compositesa.2016.10.027.  Edwards WT, Martinez P, Nutt SR. Process robustness and defect formation mechanisms in unidirectional semipreg. Adv Manuf Polym Compos Sci 2020;6:198–211. doi:10.1080/20550340.2020.1834789.  Grunenfelder LK, Nutt SR. Void Formation in Composite Prepregs-Effect of Dissolved Moisture. Compos Sci Technol 2010;70:2304–2309.  Centea T, Hubert P. Out-of-autoclave prepreg consolidation under deficient pressure conditions. J Compos Mater 2014;48:2033–45. doi:10.1177/0021998313494101.  Lynch K, Hubert P, Poursartip A. Use of a simple, inexpensive pressure sensor to measure hydrostatic resin pressure during processing of composite laminates. Polym Compos 1999;20:581–93. doi:10.1002/pc.10381.  Ma Y, Centea T, Nutt SR. Defect reduction strategies for the manufacture of contoured laminates using vacuum BAG-only prepregs. Polym Compos 2017;38:2016–25. doi:10.1002/pc.23773.  Hughes SM, Hubert P. Out-of-autoclave prepreg processing: Effect of integrated geometric features on part quality. Int SAMPE Tech Conf 2013.  Lane SA, Higgins J, Biskner A, Sanford G, Springer C, Berg J. Out-of-autoclave composite fairing design, fabrication, and test. J Manuf Sci Eng Trans ASME 2011;133:1–10. doi:10.1115/1.4004321.  Bernetich KR. Evaluation of detail part fabrication using out-of-autoclave prepreg. Proc SAMPE 2010 2010.  Dang C, Bernetich K, Carter E, Butler G. Mechanical comparison of out-of-autoclave prepreg part to conventional autoclve prepreg part. Am. Helicopter Soc. 67th Annu. Forum, 2011, p. 3–5.  Ganapathi AS, Maheshwari M, Joshi SC, Chen Z, Asundi AK, Tjin SC. In-situ measurement and numerical simulation of resin pressure during Glass/Epoxy prepreg composite manufacturing. Meas J Int Meas Confed 2016;94:505–14. doi:10.1016/j.measurement.2016.08.028.  Centea T, Hubert P. Modelling the effect of material properties and process parameters on tow impregnation in out-of-autoclave prepregs. Compos Part A Appl Sci Manuf 2012;43:1505–13. doi:10.1016/j.compositesa.2012.03.028.  Schechter SGK, Grunenfelder LK, Nutt SR. Design and application of discontinuous resin distribution patterns for semi-pregs. Adv Manuf Polym Compos Sci 2020;6:72–85. doi:10.1080/20550340.2020.1736864.  Schechter SGK, Centea T, Nutt S. Effects of resin distribution patterns on through-thickness air removal in vacuum-bag-only prepregs. Compos Part A Appl Sci Manuf 2020;130. doi:10.1016/j.compositesa.2019.105723.  Schechter SGK, Grunenfelder LK, Nutt SR. Air evacuation and resin impregnation in semi-pregs: effects of feature dimensions. Adv Manuf Polym Compos Sci 2020;6:101–14. doi:10.1080/20550340.2020.1768348.
Conference: CAMX 2022
Publication Date: 2022/10/17
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