The Effect of Mechanical Prestrain on the Creep Response of Arall ® 4 Laminates

Abstract

The paper addresses the effect of mechanical prestrain on the creep response of Arall 4 laminates at 121°C. Arall 4 is a recently developed hybrid composite belonging to the Arall family of laminates composed of symmetrically laminated alternating layers of aramid/epoxy and aluminum. This particular variant has been developed for applications involving elevated temperatures up to 150°C. It is experimentally demonstrated that the substantial extent of creep at stress levels below the proportional limit observed in Arall 4 laminates at 121°C can be significantly reduced by mechanical prestraining. Mechanical prestraining alters the residual stresses in the aramid/epoxy and aluminum layers of Arall 4 which, in turn, leads to the reduction in creep strain. An analytical model is developed which simulates the prestraining process and the creep response of the hybrid composite. The demonstrated predictive capability of the model provides the analyst/designer/manufacturer with a rational tool for optimizing the creep response of Arall 4 for the given application.