Cure shrinkage of the polymer matrix during the composite manufacturing process leads to residual stresses, which can adversely affect the structural integrity and dimensional stability of composite structures. In this paper, a novel approach is developed for measuring the resin shrinkage and strain evolution of an epoxy resin (EPON-862) in the composite manufacturing environment. The resin is cured in a custom-designed autoclave with borosilicate viewports, while digital image correlation (DIC) is used to analyze the strain evolution throughout the cure cycle. These processing induced strains are correlated to the cure-state using differential scanning calorimetery (DSC). The different mechanisms involved in the polymer strain evolution during composite processing are discussed.
In-Situ Monitoring of the Manufacturing Process and Residual Stress Evolution in Thin-Ply Composites
Thin-ply composite laminates are of interest for several applications in aerospace and other high-performance industries due to their ability to delay transverse microcracking and delamination in static, fatigue, and impact loadings. It is essential to understand the evolution of thermal residual stresses during cure to optimize the manufacturing process of thin-ply composites for deep-space applications. In this research, processing induced residual stresses in thin-ply laminates are evaluated by devising a novel in-situ experimental approach. Thin-ply prepreg laminates are cured in a specially designed autoclave with viewports with plies laid upon a flat tool and a curved tool. The curved tool configuration used in this research is designed to simulate cryogenic fuel tank surfaces. The evolution of residual stresses in terms of out-of-plane displacement is characterized using Digital Image Correlation (DIC) during the autoclave cure cycle.
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- AIAA Scitech 2021 Forum
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- National Science Foundation
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