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/θn/90]s laminate with microcracks in θ-ply and fully developed matrix cracks in 90-ply were performed under various conditions of angle θ, θ-ply crack length, θ-ply thickness, etc. Energy release rates associated with θ-ply crack propagation in the θ-ply fiber direction were calculated in order to assess θ-ply cracking conformations. The results suggested that presence of 90-ply cracks affects θ-ply crack propagation, especially mode-I energy release rates, depending on angle θ. Furthermore, effects of angle θ, θ-ply thickness and S layer configuration on the interaction between matrix cracks in θ- and 90-plies were clarified. Finally, crack accumulation behaviors in [0/θ2/90]s laminates were experimentally investigated and compared with the analytical results.