Saturation of transverse cracking with delamination in polymer cross-ply composite laminates

Delamination along the 0degrees/90degrees interface following transverse cracking in the 90degrees plies of a cross-ply composite laminate is analyzed based on the principle of minimum potential energy. The laminate is subjected to longitudinal applied tensile loading and internal residual thermal stresses. The strain energy release rate criterion has been employed to evaluate the critical applied stresses for transverse cracking and interface delamination. The effect of delamination along the 0degrees/90degrees interface on laminate stiffness and thermal property is presented for E-glass/epoxy and graphite/epoxy composite laminates. The longitudinal tensile stress in the 90degrees plies decreases gradually as the transverse crack density increases and thereby decreasing the tendency for transverse crack multiplication. For a given laminate configuration there exists a saturation (limit) crack density. Continued loading beyond this limit, delamination at the 0degrees/90degrees interface would occur. The analytical results are compared with the available experimental data.