Thermoviscoelastic Analysis of Residual Stresses and Warpage in Composite Laminates

Linear thermoviscoelastic lamination theory was used to determine resid ual stresses and warpage in multidirectional woven-glass/epoxy laminates. The single “unidirectional” layer of the material was characterized by means of an accelerated procedure. The material was assumed to be thermorheologically simple and the time-temperature superposition principle (TTSP) was used to obtain “master curves” for the viscoelastic properties. A numerical procedure was developed for determination of residual stresses and warp age, taking into consideration the irreversible polymerization shrinkage and boundary conditions during curing. Warpage was measured experimentally for [0₆/90₆] and [0₁₁/30] laminates using the projection moire method and results were in good agreement with the analytical prediction.