Effect of Post-Cure on Mechanical Properties of CF/Epoxy Composites

摘要

This paper presents the effect of post-cure on mechanical properties of CF/Epoxy composites. At first, the shrinkage strain and the mechanical properties such as Vickers hardness of resin, transverse modulus and strength are measured for carbon/epoxy unidirectional laminates after four-hour thermal treatment (post-cure process) at temperatures ranging from 70 deg C to 200 deg C. Then, the effect of post-cure temperature on transverse cracking behavior in a cross-ply laminate is experimentally investigated. The change in the residual stress due to post-cure is also estimated for the cross-ply laminate. Finally, the fracture surfaces of transverse cracks are observed using the scanning electron microcopy (SEM) to reveal the effect of post-cure on fracture behavior. It is found that the unidirectional laminate shrinks in only the transverse direction after the post-cure process. The hardness of the resin increases with increasing post-cure temperature below 150 deg C while transverse modulus and strength are independent of post-cure temperature below 150 deg C. Transverse cracking in post-cured cross-ply specimens initiates at lower stresses than the critical stresses in virgin specimens. The transverse crack density is predicted by a Weibull's probabilistic failure model. It is deduced from SEM observation of fracture surfaces that the fiber/resin interface is weakened by thermal treatment that may lead to reduction in the transverse strength at 200 deg C.