THE PREDICTION OF CRACKING IN BIAXIALLY LOADED CROSS-PLY LAMINATES HAVING BRITTLE MATRICES

For a cross-ply laminate, assuming biaxial loading and conditions of perfect bonding, it is shown how the dependence of the relevant thermoelastic constants on transverse crack density may be determined. Using energy balance concepts, it is shown how the effect of biaxial loading on transverse cracking may be determined, and how account can be taken of the thermal residual stresses. The formation of multiple transverse cracks is considered which are formed simultaneously or progressively, either at regular or random locations. It is shown how to construct non-linear stress/strain curves for axial and transverse loading assuming that the 0-degrees plies remain undamaged. The combined effect of axial and transverse applied stresses on the initiation and growth of damage in the 90-degrees plies is analysed. It is shown that the occurrence of transverse cracking can be characterized by the energy absorbed per unit volume during microcracking, a quantity which can be estimated from experimental stress/strain curves.