Durability of GFRP composites produced by pultrusion under thermal environments

Abstract

Fibre-reinforced polymer (FRP) composites have gained popularity in civil structural applications due to their advantages over traditional materials. Despite their proven better performance in harsh conditions, FRP composites are susceptible to degradation due to various environmental agents; moreover, the lack of durability data for relatively thick laminates produced by pultrusion is a concern. To address this, in the scope of the Durable-FRP project, an extensive experimental program was conducted to assess the durability of thick FRP laminates produced by pultrusion, consisting of glass fibres and unsaturated polyester and vinyl ester resin matrices, subjected to accelerated laboratory ageing and in-situ natural weathering. This paper presents preliminary results from durability tests on such glass-FRP (GFRP) laminates under particular thermal ageing environments, including constant temperatures of -15 °C, 20 °C, 40 °C, and 60 °C for a period over 12 months, as well as 100 and 200 thermal cycles between 15 °C and 60 °C. Following environmental exposure, the degradation of mechanical properties was evaluated using various tests, including tension (in both longitudinal and transverse directions), compression, flexure, in-plane shear, and interlaminar shear. In general, minor mechanical degradation was observed, except in terms of transverse tensile strength (resin-dominated) following constant exposure to extreme temperatures, with minimum property retentions of 74% and 83% at -15 °C, for vinyl ester and unsaturated polyester matrices, respectively.