Failure of cross-ply laminates with damaged matrix is analysed and their load carrying capacity is determined. Matrix damage often arises as a result of environmental effects and usually manifests itself in the form of transverse cracks which extend across the thickness of a ply. Existence of such cracks causes stiffness loss and reduction in ply strength leading to premature failure and/or shortened service life. This study aims at determining the effect of matrix cracks on the load carrying capacity of laminated composites with cross-ply layer configurations.
The cracks are modeled as aligned slit cracks across the ply thickness and transverse to the laminate plane. The distribution of cracks is assumed statistically homogeneous with a given crack density. The failure theory used in the analysis takes into account different modes of fibre and matrix failure as well as the fact that tension and compression sides of the laminate behave differently because of the opening and the closing of the cracks. The results are given for symmetrically, antisymmetrically and unsymmetrically laminated rectangular plates. The effect of problem parameters on the load carrying capacity of the laminates is studied by plotting the ratio of the failure load of cracked and uncracked laminates against the plate aspect ratio, crack density and relative layer thicknesses. It is observed that the failure load depends on the stacking sequence as well as on the relative thicknesses of layers. NOMENCLATURE a,b amn, bm, Cmn Aii, Bij, Dij C 144 61, 82 A0 V12~ V13~ V23 R. K. MAKINS and S. ADALI roots of Eqn (13) components of the reduction matrix Poisson's ratios in the xy, xz and yz planes