Influence of thermal history on transverse cracking in a carbon fiber reinforced epoxy composite

Abstract

This paper presents the influence of thermal history on transverse cracking in carbon fiber reinforced epoxy (carbon/epoxy) composites. At first, measurement of micro-Vickers hardness and Fourier transform-infrared spectrum (FT-IR) analysis of resin are conducted to investigate the effect of thermal history on resin. Secondly, shrinkage strain and transverse strength are measured for carbon/epoxy unidirectional laminates. Thirdly, the effect of temperature and duration of thermal history on transverse cracking in cross-ply laminates is experimentally investigated. The change in the residual stress due to post-cure is also estimated for the cross-ply laminates. Transverse cracking in the cross-ply specimens after thermal history initiates at lower stresses than the critical stresses in virgin specimens. It is found that thermal history increases the hardness of resin; however, it does not change the chemical structures in resin. The decrease in the strength is mainly caused by degradation of the fiber/matrix interface.