Prediction and Control of Processing-Induced Residual Stresses in Composites. Part 1. IM6/BMI Composite.

摘要

Residual stresses are developed during processing of composites due to the thermal mismatch between constituents and the chemical shrinkage of the matrix during the crosslinking reaction. Our research has shown that these residual stresses can be high enough to cause ply cracking even before loading. The objectives of the present research were to determine how residual stresses develop during processing, develop a model which would predict these residual stresses, and find an optimization scheme which would reduce the residual stresses induced by processing. The approach taken was to monitor the residual stress development through the curvature measurements in unsymmetric cross-ply specimens. The material system used was a graphite/BMI manufactured by American Cyanamid under the trade name CYCOM 3100(TM). Both elastic and viscoelastic models were used to predict the induced curvature. Mechanical testing and thermal analysis of processed specimens provided the input data for modeling. Drawing from the experimental results and analytical modeling, several cure cycle variations were proposed and investigated to reduce residual stresses. Keywords: Plastics, Thermoplastic matrix composite, Peek, Mechanical properties, Crystals, Polymers.