Finite Element Analysis of the Effect of Hygrothermal Ageing on the Mechanical Properties of Glass Fiber Reinforced Polymer Composites

Widely used in the maritime and aerospace sectors, glass fibre-reinforced polymer composites (GFRPCs) have outstanding mechanical properties, corrosion resistance, and lightweight characteristics. However, prolonged exposure to hygrothermal conditions can lead to moisture-induced degradation, adversely affecting their mechanical properties. This study investigates the impact of hygrothermal ageing on GFRPCs through experimental analysis and Finite Element Modelling (FEM) in COMSOL Multiphysics. The composite specimens were fabricated using E-glass fibers and Epoxy resin and subjected to accelerated ageing in seawater at 70°C for 60 days. Moisture absorption behaviour was analyzed according to ASTM D5229. The finite element model incorporated heat transfer and mass diffusion physics to simulate moisture ingress and its effect on mechanical behaviour. Results indicate significant reductions in Young's modulus and tensile strength, with composites exhibiting fibre-matrix debonding and matrix plasticization over time. Higher fibre weight fractions (60%) showed lower moisture absorption (2.554%), but also experienced greater internal stress concentrations, potentially leading to brittle failure. The numerical simulations validated the experimental trends, demonstrating that moisture diffusion follows Fickian behaviour, with saturation occurring near the composite surface before propagating inward. These findings highlight the need for improved protective coatings and resin modifications to enhance the longevity of GFRPCs in harsh environments.