Research On Moisture Absorption And Mechanical Properties Of Composite Materials

Application of composite materials in aerospace aircraft structure is becoming more common. However, the composite material is greatly influenced by hygrothermal environment, impact environment and the aging environment. With the development of domestic composite materials, hygrothermal and damage resistance performances of composite materials for aircraft are particularly important.This paper studied the moisture absorption and mechanical properties of composite materials. The influences of water temperatures on composite moisture absorption parameters were investigated in temperature-controlled water bath. The mechanical properties and fracture morphology of composite materials in hygrothermal environment were analyzed by bending and compression performance tests. The relationships between damage characteristics, the residual compression strength and impact energy were investigated via low-velocity impact tests and compression tests, and the appearances of damage morphology and the forms of damage after impact were observed and analyzed.Firstly, experiments of carbon fiber/bismaleimide resin composites immersed in 60? 70? and 80? water were developed respectively. According to the moisture content-time curves obtained from the experimental results, the Diffusion Coefficient and the Balanced Moisture Content of the composites immersed in different water temperatures could be calculated. What's more, the effects of water temperatures on the Diffusion Coefficient and the Balanced Moisture Content were discussed too. According to the Arrhenius equation and the law of Fick, a moisture absorption model was proposed to simulate the hygroscopic behaviours of the composite laminates immersed in different water temperatures.Secondly, the influence of hygrothermal environment on flexural property of woven carbon fiber epoxy resin composite was investigated via three point flexural test under different temperatures. Fracture morphology, dynamic mechanical property and load curve were analyzed.Besides, the influences of hygrothermal environment on compressive property of woven carbon fiber epoxy resin composite were investigated. Specimens in wet and dry state, manufactured by composite laminates, were tested under different temperature. Compressive property and failure modes were analyzed.At last, based on the low-velocity impact tests and the compression tests after impact on plain woven composite laminate at different impact energy, the relationships among the energy of impact, dent depth, damage area and residual compress strength were analyzed. The effects of different impact damage on the characteristics of compression failure through macroscopical observation at the side of the fracture on the compressed laminate were studied.