Hydrothermal Aging And The Deterioration Of Mechanical Properties Of CFRP Laminates With Voids

Carbon fiber reinforced resin matrix composites (CFRP) is widely used in theaircraft’s because of its excellent specific strength, specific modulus and comprehensiveproperties, they can effectively reduce the weight of the aircraft, improving the loadcapacity of aircraft. However, porosity defects generated during the preparation processof the CFRP laminates material will be difficult to avoid. In actual service processmaterials, together with the role of CFRP laminates porosity defects suffered byhygrothermal environment will cause greater impact on its reliability, which makes it ofgreat significance to research on the influence of hygrothermal environment on themechanical properties of CFRP with voids.This thesis studies the effects of hydrothermal aging on the static mechanicalproperties and bending fatigue performance of CFRP Laminates with different voidscontent, moisture diffusion mechanism, the hygroscopic properties under thehygrothermal environment:75℃, RH85%condition, FTIR was used to analyze thechange of functional group in polymer after hydrothermal aging, while SEM andmetallurgical microscope were chosen to find the change of microstructure of CFRPafter aging.The experimental study indicates that porosity increases will result in lower staticmechanical properties of laminates, in which the most significant reduction in flexuralstrength, and it will lead to a decrease of fatigue load increases of CFRP laminates, theabsorption curve was not changed by the porosity of different levels, with the porosityincreases, the rate of moisture absorption and the equilibrium moisture content oflaminate samples has increased. Through the absorption curve fitting analysis, foundthat the diffusion coefficient of the material will increase in porosity increases. With theincrease of porosity, the decrease of tensile strength of laminates caused byhydrothermal aging contrary reduced, the decrease of compressive strength of laminatecaused by hydrothermal aging did not significantly change. After40000times bendingload cycle effects, the bending fatigue test results shows that for the laminates which theporosity is0.3-0.7%, the decrease of the fatigue loads after hydrothermal aging becomeslarger, but for the1.2-2%of the porosity of the laminates, results contrary. As can beseen from the FTIR that the polymer didn’t undergo any chemical reaction.