Analysis of how thermal aging affects the long-term mechanical behavior and strength of polymer-matrix composites

The use of polymer-matrix composites for aeronautical applications with a long service life led to examining the couplings between thermomechanical loading and thermal aging effects. Thermal aging gives rise to complex phenomena on molecular scale that can considerably alter the mechanical properties and reduce the lifetime of composite materials. This paper describes our approach for taking into account the different aspects (viscoelastic behavior, thermomechanical damage, degrading resulting from physical and chemical aging) in a multiscale model. The material investigated is a carbon fiber/epoxy matrix composite (IMS/977-2) in the class of materials being considered for the future SST. The aim is to develop a macroscopic model that can be used for finite element structural computations.