Optimal Cool-Down in Linear and Nonlinear Thermoviscoelasticity and the Effects of Initial Stress

Abstract

This article concerns the minimization of residual thermal stresses in geometrically constrained adhesive layers and thin polymeric composite lay-ups with emphasis on the role of initial stresses. Such residual stresses evolve during cure and subsequently during post-cure cool-down. The cure stresses play the role of initial stress superimposed on the thermoviscoelastic response that governs to cool-down phase. Optimization is achieved by following a time-temperature path that achieves the best counter play between temperature as a stress inducing and a stress reducing agent. When viscoelastic nonlinearity is considered such contradictory effect is played by stress itself, in which case an initial stress may have a beneficial effect.