Minimizing environmental degradation in fracture toughness of carbon fiber/epoxy composites using carbon nanotubes

Abstract

Environment assisted degradation in mechanical properties is a major concern for the integrity of composites in structural applications. Experiments are performed to examine the efficacy of carbon nanotubes (CNTs) to counter the adverse effect of environmental conditions on the fracture toughness of carbon fiber/epoxy composites (CFRP). Composite coupons are exposed to accelerated weathering cycle for varying durations. Experimental testing shows that the fracture toughness degrades significantly after exposure to aging cycle. The addition of CNTs minimizes the adverse effect of weathering. The comparable fracture toughness of 1000 hrs aged CNT modified CFRPs with the unaged conventional CFRPs suggest that the advantages of CNT addition persist even after exposure to prolong weathering conditions. Fractography analysis reveals that the CNT induced toughening of epoxy improves Mode I and Mode II fracture toughness of conventional CFRPs. While the fracture in conventional CFRP is primarily at fiber/matrix interface, textured microflow, larger sized cusp and matrix cracking are observed in CNT modified CFRPs.