The Effects Of Voids On The Fatigue Of Carbon Fiber Epoxy Reinforced Resin Composites

With the development of science and technology,carbon fiber reinforced polymer (CFRP) has gradually become the important structure materials of aerospace field owing to their advantages such as high values of specific strength and high specific modulus,fatigue resistance,impact resistance,good processing property and easy to design.Besides,fatigue property of fiber reinforced polymer has important influence on its application.However,with the widespread use of composite materials, because of materials poor stability resistant to hot-moist environment,lots of strength shortcomings related to materials,the problem of materials fatigue and durability, internal void defects of material structure is not easy to control,limiting applications of CFRP in aerospace filed.Void is the most common tiny defect of composite materials. Porosity are closely related to composite materials property,generally speaking,the higher porosity, the lower anti-fatigue capability, also,much more sensitive to the permeate of water and atmospheric.This article summarizes the research situation of void and composite materials fatigue properties of domestic and overseas.Analyzes different porosity of composite materials influence on flexural strength, flexural strength and flexural residual strength.The law of the room temperature,hot-moist environment, dehumidification influence to materials flexural strength and the bending fatigue property were also discussed.Through the modification of apparent condition, mechanical properties and microstructure of materials,evaluating the influence on fatigue properties of porosity.This experimental results show that at room temperature environment,with the increase of porosity,the decline of maximum stress will be gradually increased,and fatigue life cycle will be gradually decreased, the influence of porosity to fatigue strength is much bigger than static state.Under hot-moist environment,the maximum absorption volume increased with the increasing of porosity, porosity is an important factor to decide hygroscopic characteristics of composite materials.The sensitivity of moisture absorption also decided on void's distribution, shape and the hydrophilic of matrix material,as increasing of time, with the increase of porosity, flexural fatigue strength will in a gradually decreasing process.the influence of porosity to fatigue properties is relevant to the critical size and shape of voids are in the high stress area.In dehumidifying environment,with the increase of porosity,flexural fatigue residual strength will in a gradually decreasing process,when composite materials dry again after moisture absorption,the changes of mechanics performance for moisture absorption can be partial recovery.