GOD-based simulation of transverse cracking and stiffness reduction in [S/90(n)](s) laminates

Closed-form expressions for the thermo-elastic properties of [S/90(n)](s) l aminates with transverse cracks in the 90 degrees layers are derived. Provi ded the normalised average crack-opening displacement (COD) is known, expre ssions contain only crack density, geometrical parameters and elastic const ants of layers. The average COD dependence on the crack spacing and constra int effect of adjacent sub-laminates is analysed by using finite-element me thod in plane stress formulation. It is found that the out-of-plane elastic constants have an insignificant effect on GOD. A simple power law relating average COD to elastic and geometrical parameters of constituents is deriv ed. The obtained power law and the developed methodology are successfully u sed to predict the reduction of thermo-elastic properties and damage evolut ion of [+/- theta /90(4)](s) laminates. The crack-closure technique and Mon te-Carlo simulations are used to model the damage development. The 90 degre es layer is divided in to a large number of elements and G(c) values are as signed to each element according to a Weibull distribution. Parameters in t he Weibull distribution are determined by using experimental crack density versus strain curve for glass-fibre/epoxy [0(2)/90(4)](s) cross-ply laminat es. Damage development in [S/90(4)](s) laminates of the same material, cont aining sub-laminates with +/- theta layers only, is modelled by using these Weibull parameters and the results are in good agreement with test data. T he effect of the thickness of the 90 degrees layer on damage development is discussed in strength and fracture mechanics formulation. (C) 2001 Elsevie r Science Ltd. All rights reserved.