Natural Weathering of GFRP Structures: Case Studies, Data Survey, and Proposal of a Moisture Conversion Factor for Durability Design

Abstract

This paper defines a conversion factor included in the European technical specification for the design of fibre–polymer composite structures that considers the effects of moisture on the mechanical properties of fiber-reinforced polymer (FRP) composites exposed to natural weathering. The first part of the paper presents a field investigation about the durability of four pultruded glass fiber–reinforced polymer (GFRP) structures in service for 11–22 years in a Mediterranean climate. Their performance was evaluated by dynamic mechanical analysis and mechanical tests on small-scale coupons. The changes of thermophysical and mechanical properties showed low-to-moderate degradation. The second part of the paper presents the design-oriented methodology to define the moisture conversion factor. The results from the experimental study and those gathered from a literature data survey on the retention of mechanical properties of FRP materials after long-term exposure to natural weathering were analyzed. Based on these data and statistical considerations, a value of 0.85 was adopted for the natural weathering moisture conversion factor.