Hygrothermal degradation of modes I and II fracture toughness in flat carbon/epoxy composites: experimental and numerical insights

Filament winding is a widely used technique for manufacturing axisymmetric fibre-reinforced composites, such as pressure vessels and pipes, designed for harsh environments. Understanding the effects of these conditions on mechanical performance is crucial. This study presents a combined experimental and numerical investigation of unidirectional carbon/epoxy composites manufactured via filament winding, subjected to tensile, compressive, shear, and interlaminar fracture toughness tests (Modes I and II). Samples were exposed to hygrothermal ageing at room and elevated temperatures to assess moisture absorption and its influence on fracture properties. Special attention is given to the variation in interlaminar fracture toughness due to hygrothermal exposure. Fractographic analysis reveals fibre bridging as a key mechanism behind enhanced Mode I toughness, while Mode II toughness deteriorates with ageing. The findings provide critical insights into the durability and failure mechanisms of filament-wound composites under service conditions.