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20th International Conference on Composite Materials Copenhagen, 19-24th July 2015 deficiencies. In contrast, processing deficiencies did not clearly affect corner thickness deviation. Corner thickening was observed in all cases and was primarily driven by inter-ply friction given a range of factors common to convex corner processing. Of particular note regarding the thickness deviation analysis, scanned images of sample cross- sections were processed via a custom image processing and dimensional analysis code in order to generate full thickness profiles. This approach improved thickness measurement accuracy and precision by removing human error and refining measurements, in addition to generating a more comprehensive picture of local thickness variations and partly automating the measurement process. In the second part of this work, processing deficiencies were shown to yield lower curved beam strengths (CBSs), with restricted air-evacuation again being the worst processing case. In turn, the UD tape was significantly more affected by processing deficiencies than the woven prepregs. The wavier surface topography of bidirectional woven prepregs was visually shown to impede delamination growth and lowered void-sensitivity in contrast to UD tape. Lastly, UD laminates processed under the near-optimal baseline condition failed at a markedly higher CBS, though conversely resulted in much higher data scatter, which was linked to a lower probability in there being critical voids in the region of maximum radial stress [26]. Very large data scatter in CBS data (typically >> 10%) ultimately mitigates superior mechanical performance: larger knockdown factors are required, which can level performance across fibre architectures. This levelling in performance possibly renders woven prepregs potentially more attractive for use in complex-shape laminates, as secondary benefits (faster layup, improved draping-ability, etc.) take more precedence. Overall, these conclusions bring additional clarity to the relationship between fibre architecture, local thickness deviation and macro-porosity, and interlaminar tensile behaviour for several commonly encountered process conditions. Of great future research interest will be the testing and analysis of similar concave laminates. The combined experimental data and observations will found the basis of future work on predictive thickness deviation and mechanical performance tools. ACKNOWLEDGEMENTS The authors would like to first and foremost acknowledge the in-kind contribution of Bombardier Aerospace in supplying OOA prepreg materials and vacuum-bagging consumables. Of equal importance is the financial support of: 1) the Natural Sciences and Engineering Research Council of Canada (NSERC) under the G8 Research Councils Initiative on Multilateral Research Fundin (grant: G8MUREFU2 – Material Efficiency, A First Step Toward Sustainable); and 2) the Centre de Recherche sur les Systèmes Polymères et Composites à Haute Performance (CREPEC). Last but not least, the authors wish to recognize the many members of the McGill Structures & Composite Materials Laboratory for their varied support. REFERENCES [1] P. Hubert, G. Fernlund and A. Poursartip, Autoclave processing for composites, in Manufacturing techniques for polymer matrix composites (PMCs) (Eds. S.G. Advani and K.-T. Hsiao), Woohead Publishing Ltd., Cambridge, 2012, pp. 414-432. [2] G. Gardiner, Out-of-autoclave prepregs: Hype or revolution? Oven-cured, vacuum-bagged prepregs show promise in production primary structures., Composites World, Gardner Business Media Inc., 2011, Cited May 13, 2015, Available: http://www.compositesworld.com/articles/out-of-autoclave-prepregs-hype-or- revolution. [3] J. Schlimbach and A. Ogale, Out-of-autoclave curing process in polymer matrix composites, in Manufacturing techniques for polymer matrix composites (PMCs) (Eds. S.G. Advani and K.-T. Hsiao), Woohead Publishing Ltd., Cambridge, 2012, pp. 435-481. [4] R. Stewart, Carbon fibre market poised for expansion, Reinforced Plastics, 55, 2011, pp. 26-31 (doi: doi:10.1016/S0034-3617(11)70216-8). [5] L. Repecka and J. Boyd, Vacuum-bag-only-curable prepregs that produce void-free parts, Proceedings of the SAMPE 2002 47th International Symposium and Exhibition (Eds. B.M. Rasmussen, L. Pilato and H.S. Kliger), Long Beach, CA, United States, May 12-16, 2002, SAMPE, Covina, 2002, pp. 1862-1874.PDF Image | VACUUM-BAG-ONLY COMPLEX-SHAPE PREPREG LAMINATE
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