Consecutive matrix cracking in contiguous plies of composite laminates

Propagation behaviors of obliquely-crossed microcracks induced by matrix cracks in adjacent plies of composite laminates were numerically analyzed using finite element modeling. Oblique coordinate system along obliquely-crossed cracks was defined and applied to the finite element formulation, which enabled geometrically parametric analysis for arbitrary oblique angles using a single discrete model. Three-dimensional stress analyses of [S/hn/90]s laminate with microcracks in h-ply and fully developed matrix cracks in 90-ply were performed under various conditions of angle h, h-ply crack length, h-ply thickness, etc. Energy release rates associated with h-ply crack propagation in the h-ply fiber direction were calculated in order to assess h-ply cracking conformations. The results suggested that presence of 90-ply cracks affects h-ply crack propagation, especially mode-I energy release rates, depending on angle h. Furthermore, effects of angle h, h-ply thickness and S layer configuration on the interaction between matrix cracks in h- and 90-plies were clarified. Finally, crack accumulation behaviors in [0/h2/90]s laminates were experimentally investigated and compared with the analytical results.