Evolution of the Impact Strength of Carbon Fiber-reinforced PEI Following Exposure to Mechanical, Hygrothermal and Hygrothermomechanical Aging

Abstract

The instrumented impact test in a falling weight tower was used to obtain the influence of hygrothermal exposure (temperature and humidity), mechanical exposure (flexure load) and the addition of both types of aging (hygrothermomechanical) on the impact properties of a composite with a thermoplastic matrix reinforced with carbon fiber fabric. During the tests, the Charpy specimens employed were positioned so that the hammer struck the piled up plies of the composites transversely. This condition contributed to delamination along the planes of the interface. The energy obtained has two components: initiation and propagation. These components must be calculated independently and could be used to evaluate the behavior of the material subjected to these types of exposure. An analysis was carried out of the specific advantages of this test method in composite materials. From the results, it can be deduced that the fracture toughness of the material does not suffer substantial variations if the exposures are independent. However, their combined action does modify the behavior of the material; in which case, a significant decrease in toughness can be observed.