Hygrothermal ageing of pultruded GFRP profiles: Comparative study of unsaturated polyester and vinyl ester resin matrices

Abstract

The durability of pultruded GFRP composites is critical to their performance in civil engineering applications, for which comprehensive and validated data is limited. To address this issue, this study presents an extensive experimental programme on the effects of hygrothermal ageing on the performance of pultruded GFRP profiles made of two alternative resin systems – unsaturated polyester (UP) and vinyl ester (VE) – both comprising identical fibre architecture. The ageing environments included immersion in demineralised and salt water at three different temperatures (20°C, 40°C, and 60°C), and continuous condensation at 40°C, for durations up to two years. Physical, viscoelastic and mechanical (tensile, flexural, in-plane and interlaminar shear) properties were assessed after a desorption period. As expected, the VE profile had overall better performance than the UP profile. After 24 months, the highest reductions in tensile strength occurred for water immersion at 60°C, namely 45% and 33% for the UP and VE profiles, respectively. This paper provides a wealth of test data that can be used for degradation models for the prediction of their long-term mechanical property retention.