Effect of prolonged isothermal exposure and thermal cycling on mechanical properties and shape recovery behavior of shape memory polymer composites

This study investigated the thermal environmental durability of carbon fiber reinforced epoxy-based shape memory polymer composites (SMPCs) under isothermally elevated/cryogenic temperatures and thermal cycling. The mechanical properties and shape memory behavior of the SMPCs were evaluated through quasi-static tensile tests, cyclic tensile tests, and shape recovery experiments. Findings indicated some variations in mechanical properties during environmental exposure. Isothermal low-temperature exposure enhanced mechanical properties, while thermal cycling significantly reduced them due to residual thermal stresses at the fiber/matrix interface. Cyclic tensile tests showed that thermal exposure influenced cyclic mechanical properties, including cyclic life, hysteresis loop evolution, and modulus degradation. Despite these changes, the shape memory performance remained largely unaffected by prolonged isothermal exposure or thermal cycling, exhibiting only a slight delay in shape recovery response and a minor reduction in shape recovery rate (<4%).