Thermal Residual Stresses Induced During Manufacturing Process of Fiber Reinforced Polymeric Composites

The evolution of thermal residual stresses induced during curing processing has been investigated. A micro-mechanical model of a cross-ply laminates is analyzed using viscoelastic finite element method. The polymer matrix is represented by a non-linear viscoelastic constitutive model. To study possible bounds of the residual stresses two types of analyses were carried out: one with temperature-independent and the other with temperature-dependent material constants. The results indicate that a higher cooling rate results in higher residual stresses in the laminates. However, due to the viscosity of the polymer matrix, the residual stresses relax with time and tend to an asymptotic small value irrespective of the different cooling rates. The average shrinkage strains and the coefficients of thermal expansion (CTE) of the composites, correspondingly, are also time-dependent and approach an asymptotic value after the stress relaxation process.