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UBC Theses and Dissertations

Process induced deformation of composite materials : an experimental methodology, systematic review and meta-analysis Tao, Yuping


The ability to consistently produce composite structures with controlled tolerance remains a challenge for commercial aerospace applications. Dimensional discrepancies between the true geometry and designed geometry leads to custom shimming processes or forced assembly, which can be costly and/or reduce structural performance. Thus, further understanding and better management of process-induced deformation (PID) is needed. In the present work, process induced deformation, manifesting itself as spring-in and warpage of L-shapes, is studied experimentally. A rigorous methodology is developed to address the gaps in the literature and identify the variabilities in the composite manufacturing processes. The methodology includes an accurate and automated analysis method whereby point cloud data of the L-shapes obtained by laser CMM is processed to distinguish the nuances of spring-in and warpage. Processing parameters such as laminate dimensions and cure cycles, which have been under-studied or the cause of disagreement, are shown to have meaningful impact on PID. The second half of the work presents a systematic review conducted for 94 experimental studies and over 2000 process induced deformation specimens from the open literature. This dataset is believed to be representative and as thorough as possible. A meta-analysis was performed on a subset of specimens made with three materials systems: HEXCEL AS4/8552, TORAY T800/3900-2 and CYCOM IM7/5320-1. This systematic review reveals disagreements within the PID literature and highlights the high variability in the composite manufacturing process which hinders direct comparison across studies and full understanding of PID. The meta-analysis investigates the data consistency, and probes the influences of laminate thickness, layup type, gelation temperature and other processing parameters, providing insight into the spring-in phenomena as seen by the combined literature.

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