1993 Volume 42 Issue 475 Pages 398-404
FRP (Fiber Reinforced Plastics) are most popular and widely used materials among various kinds of composites. In many kinds of FRP composites, SMC materials are frequently used as materials for various equipments. Most SMC materials are also used in various environmental conditions, such as water, ultraviolet rays, oxgen and so on. Among these conditions, water environment is a usually surrounding one around these materials and it strongly influences SMC materials' properties. Therefore, in this paper, the effects of water absorption on the fatigue properties and inner structural changes of SMC materials were investigated. In this study, SMC material composed of bis phenol A unsaturated polyester resin and E-glass chopped strand mat was used. Voids which were generated during molding process were recognized to exist in the central layer of SMC material. SMC specimens absorbed 3.0% water after 10800 hours immersion into deionized water at 30°C, and the water absorption process is shown to follow Fick's law. Fatigue life in water environment of SMC material becomes extremely short comparing to that obtained in air. As the results of SEM observation and EPMA (Electron Probe Micro Analyzer) analysis on the fracture surface, it was made clear that the absorbed water in SMC material reacted with calcium carbonate which was distributed in the matrix resin as filler. Then, the absorbed water penetrating through the dissolution regions. into inner sites caused the degradation of interfacical bonding between fiber and matrix in SMC material.
