A Numerical Study of the Compression and Shear Failure of Woven Carbon-Carbon Laminates

A finite element analysis was performed to determine the influence of microstructural inhomogeneities on the compressive and shear strength of 2-D carbon-carbon laminates. In particular, the effects of amplitude and distribution of the fiber bundle crimps, and lengths and distribution of the interply and transverse bundle cracks are determined. The results of the numerical study are successfully compared with experimental observations made in an earlier study under compression and shear loading. Under a warp-aligned compression load, the local material parameter which controls the overall instability in the form of multiple interply delaminations is the critical energy release rate for growth of pre-existing interply cracks, except for when the maximum length of these cracks is less than 0.6 mm when the failure is through bundle kink-induced shear faulting. For all pre-existing crack lengths, the same parameter was responsible for initiating a planar shear fault following the crimp boundaries under an interlaminar shear loading. Accordingly, the numerical cell-model considered here conforms to the above mechanism by allowing the participation of the energy release rate as the failure parameter.