Void formation at the fiber/matrix (F/M) interface is known to be a primary structural defect in a composite material. It is a major factor that contributes to the water uptake in composite materials for underwater applications. We develop a mathematical model to describe the kinetics of water uptake in unidirectional fiber reinforced resin composites containing voids. By using a one-dimensional two-phase fluid flow model with parameters derived from Microcomputed X-ray tomography (µCT), we predict the water wicking process in carbon/vinylester (CF/VE) panels containing capillary voids at the F/M interphase. The capillary driven flow is impeded by viscous forces and the compressed air bubble, trapped between the two flow fronts. In particular, our calculation indicates that the effective contact angle at the F/M interface in CF/VE composite is 29.7 ± 0.1° for the equivalent capillary radius of 1.2 µm. The results are validated by comparing the simulated water absorption to the experimental data for CF/VE composite specimens of three different sizes immersed in sea water.

已知在纤维/基体（F / M）界面处的空隙形成是复合材料中的主要结构缺陷。这是导致水下应用复合材料吸水的主要因素。我们开发了一个数学模型来描述包含空隙的单向纤维增强树脂复合材料中水分吸收的动力学。通过使用一维两相流体模型，其参数来自微计算机X射线断层扫描（µCT），我们可以预测碳纤维/乙烯基酯（CF / VE）面板在F / M相中包含毛细孔的水芯吸过程。毛细作用力驱动的流体受到粘滞力和压缩气泡的阻碍，而这被困在两个流动前沿之间。特别是，我们的计算表明，CF / VE复合材料在F / M界面的有效接触角为29。对于1.2 µm的等效毛细管半径，为7±0.1°。通过将模拟的吸水率与三种不同尺寸的CF / VE复合材料样品浸入海水中的实验数据进行比较，可以验证结果。