This study examines the diffusion of water in fiber-reinforced polymer (FRP) laminated composites, comprising epoxy resin and unidirectional glass fibers, at different material and structural scales. Experiments on the diffusion of neat resin, FRP laminas in the axial and transverse fiber directions, FRP laminated composites with different stacking sequences, and FRP plates, rods, and pipes are conducted to obtain the diffusion processes at different length scales. Simultaneously, a diffusion model for a laminated composite is formulated to mathematically describe the multi-axial diffusion processes in FRP composites at various length scales, i.e., single lamina, laminated stacking sequence, and component. The study shows that the diffusivity constants calibrated from neat epoxy resin and unidirectional laminas are adequate to predict the diffusion responses of laminated composite systems and structural components of larger sizes. This capability is useful in predicting the long-term diffusion responses of FRP composites of complex geometries and large sizes where conducting diffusion tests on such systems is not feasible.

这项研究研究了水在纤维增强聚合物（FRP）层压复合材料（包括环氧树脂和单向玻璃纤维）中在不同的材料和结构规模下的扩散情况。进行了纯树脂，FRP薄片在轴向和横向纤维方向上的扩散，具有不同堆叠顺序的FRP层压复合材料以及FRP板，棒和管的扩散实验，以获得不同长度尺度的扩散过程。同时，建立了层压复合材料的扩散模型，以数学方式描述了FRP复合材料在各种长度尺度下的多轴扩散过程，即单个薄片，层压堆叠顺序和组件。研究表明，用纯净环氧树脂和单向薄片校准的扩散常数足以预测层压复合系统和较大尺寸结构部件的扩散响应。此功能可用于预测复杂几何形状和大尺寸的FRP复合材料的长期扩散响应，而无法在此类系统上进行扩散测试。