ENERGY-BASED ANALYSIS OF TRANSVERSE CRACKING AND INDUCED DELAMINATION IN [S'/90n/S]s LAMINATES: A VARIATIONAL APPROACH

Abstract

Analysis of transverse-ply cracking and small delaminations emanating from the tips of transverse cracks is extended to symmetric laminates having more general layup configurations. Almost all studies on induced delamination due to transverse-ply cracking are limited to [S/90n]s laminates, where (S) is any orthotropic sublaminate that is much stiffer than [90n]. In this paper, the evolution of transverse matrix cracking and the induced delamination from it is investigated for laminates with more general layups [S'/90n/S]s. In this configuration, the cracked layer is offset to the midplane of the laminate and is constrained by the two orthotropic sublayers. The micromechanics-based model is developed using a variational approach to find the stress field of a unit-cell in a generalized plane strain condition. A combined analytical/numerical methodology is used to solve the boundary value problem. The total complementary potential energy of the unit-cell is calculated, as is the energy release rate for transverse cracking and induced delamination damage. The calculated energy release rate as a function of crack density and delamination length is obtained for different layup configurations, and in some cases the results are compared with results from the literature. Because the distribution of cracks in a structure is uniform, the results for the unit cell scale can be used for the structural scale.