Modeling of composite interfaces subjected to thermal stresses and physical aging

Abstract

Coupling between internal stress and the aging process is of considerable importance to characterize the durability of a composite. The present work investigates how interfacial properties are modified upon physical aging, using single fiber model composites. Firstly, the micro-mechanics of the interface and their evolution upon aging are studied through the microbond test. Secondly, this theory is coupled to that of the energy release rate and their equivalence is assessed by experimental investigation. These methods were tested in the case of freshly cured and aged epoxy droplets on glass fibers, and were shown to yield similar results. Providing that the relaxation of internal stresses and the shift of relaxation times of the matrix when it is physically aged are accounted for, the interface is described by one single parameter. This allows the determination of the intrinsic shear strength of the interface and its energy release rate.