Empirical models for matrix cracking in a CFRP cross-ply laminate under static- and cyclic-fatigue loadings

This paper presents empirical models for predicting matrix crack density in a carbon fiber reinforced plastic (CFRP) cross-ply laminate under static-fatigue and cyclic-fatigue loadings. First, a modified slow crack growth (SCG) law, that covers the whole range of stress ratio R of tension-tension fatigue (0 ≤ R a;circ 1), was proposed. The modified SCG law and three conventional SCG laws were then combined with Weibull's probabilistic failure concept for predicting fatigue matrix crack density in a cross-ply laminate. Matrix crack density was expressed as a function of R, the maximum stress in the transverse ply and the number of cycles. Next, fatigue tests were performed for R of 0, 0.2, 0.4, 0.6, and 1 to determine the applicability of these four models. Finally, constant fatigue life (CFL) diagrams were investigated based on the modified model.