Effect of Thermal Shock on Modulus of Thermally and Cryogenically Conditioned Kevlar/Polyester Composites

Abstract

The interfacial adhesion between fibre and matrix has a dominating effect on the overall performance of a composite. The matrix shear yielding, interfacial debonding or some combination of both may be reflected in the short beam shear (SBS) test. The bond between a fibre and the surrounding matrix can be weakened by exposure to active environments. But Kevlar 49 has been specifically engineered for polymer reinforcement and is intended more for the aerospace industries, primarily to achieve significant weight reduction without compromising performance [1, 2]. It is generally believed that the polymer is likely to be tough if homogeneous yielding occurs. Even brittle crack propagation in polymers usually involves localised viscoelastic and plastic energy-dissipating processes taking place in the vicinity of the crack tip [3]. Brittle thermoset resins, such as unmodified epoxy and polyester, may undergo only a limited extent of deformation prior to failure. The propagation of the debonding cracks may involve breaking of the primary and secondary bonds between the fibre and the polymer matrix. It should be noted that multiple matrix cracking may represent a significant source of toughness.