model for stiffness reduction in cross-ply laminates based on generalized plane strain assumptions is developed. Simple analytical expressions are obtained for longitudinal modulus and Poisson's ratio reduction as a function of transverse crack density. Additionally to the crack density, these expressions contain only elastic and geometrical properties of constituent laminae and the average crack opening displacement (COD) normalized with respect to the far-field strain. Calculations of COD are performed using FEM and several analytical models based on shear lag assumptions and variational analysis. Their predictive capabilities are verified using comparison with experimental data and FEM results. A simple procedure is suggested for COD determination, requiring for a given material only one FEM calculation using 'an average laminate' with 'an average crack spacing'. The obtained COD is used with good results for stiffness prediction for a wide variety of laminates of this material