Meso-level manufacturing process simulation of sandwich structures to analyze viscoelastic-dependent residual stresses

This article presents a simulation method to analyze process-induced stresses of a meso-level unit cell of a pin-reinforced sandwich structure (carbon fiber-reinforced plastics/foam). During the manufacturing process, different mechanisms lead to process-induced deformations and stresses. These mechanisms depend on thermal expansion, shrinkage, nonlinear viscoelastic properties of the material, and variation in local temperatures. In critical cases, these residual stresses can lead to initial degradation and up to failure of the material. This article demonstrates a method to perform a sequential coupled thermo-mechanical analysis of the manufacturing process with focus on the correct determination of stresses and description of the viscoelastic relaxation effect. A novel approach to take into account anisotropy of characteristic relaxation times dependent on the cure process is presented.