Study on Hygrothermal Aging of Glass Fiber/Epoxy Composites Fabricated From Dual‐Axis Warp‐Knitted and Flat‐Weave Woven Prepregs

ABSTRACT This study innovatively developed biaxial warp‐knitted glass fiber/epoxy prepregs using a hot‐melt process and systematically compared them with conventional plain‐woven prepregs of identical specifications. Under 85°C/100% RH hygrothermal aging conditions, the prepreg‐derived composites exhibited distinct degradation behaviors: The biaxial prepreg composites showed 9.5% higher initial tensile strength (508.8 MPa vs. 464.6 MPa) but greater moisture absorption (6.10% vs. 5.50%), resulting in lower strength retention after 800‐h aging (43.5% vs. 55.4%). DMA analysis revealed a more significant glass transition temperature reduction in biaxial prepreg composites. SEM observations demonstrated that the open architecture of biaxial prepregs accelerated interfacial degradation, while the tight weave structure of plain‐woven prepregs effectively hindered moisture penetration. This work provides critical guidance for selecting prepreg architectures in humid environments.