Microlevel manufacturing process simulation of carbon fiber/epoxy composites to analyze the effect of chemical and thermal induced residual stresses

A micromechanical implicit finite element analysis using Samcef/Mecano was performed to analyze the effect of process-induced deformations and stresses on a unidirectional carbon fiber-epoxy composite material (G1157/RTM6). During the manufacturing process, chemical and thermal shrinkage deformations occur and lead to internal stresses. In this article, several effects on the level of stress on the microscale will be discussed, which address the nonlinear behavior of the polymer matrix material. A parametric study was done on the influence of these effects on residual stresses including temperature dependency of the young's modulus, thermal expansion coefficient, nonlinear thermomechanical stress-strain behavior, microyielding, microdegradation, and viscoelasticity. Several experiments have been carried out to investigate the thermomechanical behavior of the matrix material and to derivate constitutive equations. The derived equations and the discussed effects are integrated into an analysis model of a squared unit cell and used to perform a coupled curing thermomechanical simulation. As a result, the development of process-induced stresses is presented with the integration of nonlinear local material effects. Assessment of these effects is one of the key aspects for interpretation of process-induced stresses on the macroscale.