Hydrothermal Aging of Glass Fiber Reinforced Thermoplastic Composites

Abstract

Continuous fiber-reinforced polymer composites (FRPC) are commonly made with a thermoset polymer matrix; however, thermoplastic matrix materials are increasingly employed as an effective substitute in recent years. FRPC used in structural applications are often exposed to water and humid environments, which may deteriorate their mechanical performance. Both thermoset and thermoplastic matrices offer considerable resistance to water ingress, yet, moisture exposure may significantly affect material performance during long-term exposure. These situations become more severe at higher temperatures, where degradation phenomena will be accelerated. Thus, knowledge of the extent of strength reduction under these conditions is a vital input to the engineering design of durable structures. The present study investigates the durability of unidirectional glass fiber reinforced composite tapes made with either a polypropylene or high-density polyethylene matrix, by conditioning samples in deionized water for up to 8 weeks at 60°C and 95°C. Water uptake behavior and tensile strength were measured. The focus of this work is to increase the understanding of damage effects that occur to the fiber matrix interphase and the glass fibers, as these components chiefly dictate the performance of the composite. Mechanical testing was performed on dried material samples after aging. Chemical elements that may have leached into the aging fluid during conditioning were analyzed, and virgin and aged samples were characterized to explore the responsible mechanism for fiber degradation by environmental aging.