Optimum design of laminated composites subjected to hygrothermal residual stresses

Abstract

Residual stresses in composite laminates depend on the thermoelastic properties of the material and processing temperatures. The distribution of these stresses in the various laminates is a function of the stacking sequence and ply orientation. This paper presents a theoretical investigation of the effects of hygrothermal residual stresses on the optimum design of laminated composites. Angle-ply laminates, cross-ply laminates and quasi-isotropic laminates have been considered and these laminates are subjected to different mechanical, thermal and hygroscopic loading conditions. Optimum laminate configurations have been determined by using non-linear optimization algorithms offered by the program OPTICOM. Residual stresses and strains in different layers of laminates are calculated using classical laminate theory and laminate strength ratios are determined by using the Tsai-Wu failure criterion. Hygrothermal effects on minimum thickness and in-plane strength of the laminates are then demonstrated. Analysis of the results indicates that the prediction and measurement of residual stresses are important in relation to production, design and performance of composite structures.