Specificity of matrix cracking development in CFRP laminates under mechanical or thermal loadings

Fatigue tests at room temperature and thermal cycling experiments have been performed on carbon/epoxy laminates of cross-ply and complex stacking sequences. An ‘equivalent’ fatigue loading level has been evaluated in order to impose on the 90° plies the same amplitude of transverse stress σ22 than in thermal cycling. A comparison of the matrix crack development throughout both types of tests has been undertaken: they have been found analogous, but with very far much faster kinetics under thermal cycling. Moreover, the fatigue test frequency has a significant influence on crack onset and development. However, it seems that the parameters ‘time’ and ‘transverse ply stress amplitude’ are not sufficient to completely explain the very fast cracking kinetics observed under thermal cycling.