Visual Experiments for Water Absorbing Process of Fiber-Reinforced Composites

Abstract

It is important to understand the aging mechanism of composites for their use in wet and thermal environments. Many researchers have carried out experiments or applied mathematic methods, such as finite element analysis (FEA) and Fick-diffusion law to establish a water-absorption-mechanism-model of composites. However, some visual experiments of the process have not been provided up to the present. In this paper, substituting CuSO4 powder for resins, visual experiments were carried out to qualitatively simulate the capillarity and watersorption process of a few fiber-reinforced composites under wet and thermal environments. In experiments, three kinds of fibers were used: amide fiber (including kevlar29 and kevlar49), poly- p-phenylenebenzobisoxazole fiber (PBO fiber), and carbon fiber (T300). The results showed that because of the capillarity, water molecules will enter rapidly the interface of composites between fibers and resin, and at the same time diffuse into the resin. Therefore, the interface is badly damaged and the performances of whole composites decrease after the process. The aim of our experiments is to prove the process visually in a unique technology.