Hydrothermal Aging Effect Study Of Waterproof Coating’s Effect On Carbon Fiber Reinforced Epoxy Resin Composites

Carbon fiber (CF) composite material has been widely used in aeronautical industry due to its good mechanical properties, excellent fatigue resistance and design-ability.Carbon epoxy composite material has strong corrosion resistance but it can also be corroded. The combined effect of oxygen, moisture and sun-light (especially ultraviolet (UV)) are the most important ambient factors. The damp-heat and UV aging behavior will affect the properties of carbon fiber composite, parts and structure will be changed and damaged under the affect, which will in turn affect the properties of CF composite material.In this paper, the accelerated aging test was carried out in damp-heat ambient according to GJB150“Laboratory equipment test methods for military materiel”. The ultraviolet radiation aging test was proceeded according to GB/T 14522-93”Artificial accelerated ageing test method for plastics, coatings and rubber materials used for machinery industrial products”. The composite aging processes was researched by quality change, mechanical properties changes surface morphology changes before and after test. The changes of testing sample with or without epoxy paint protector were also considered. It provides a theoretical verification for environmental adaptability research of military equipment.The humid resistance test shows that the weight gain rate of CF composite materials increase constantly by time, interfacial bonding between carbon fiber and epoxy resin is weaken by water absorption , composite mechanical strength decreases with aging escape The weight gain of CF composite material in thermal and humid environment was mainly affected by moisture absorption. In the first stage of moisture absorption, composite materials mechanical strength decrease obviously. When the moisture sorption equilibrium was achieved, mechanical strength maintained on a fixed value. The inter-laminar shear strength of CF composite materials with coating dropped to 93.2% and the flexural strength dropped to 89% after 15 days of damp- heat aging .While the inter-laminar shear strength of CF composite materials without coating dropped to 86.6%, the flexural strength dropped to 88.7%. The UV aging test showed that weight gain rate of CF composite materials in UV environment is mainly affected by moisture absorption; the thermal aging of resin composites is also an important factor. The weight gain rate of graphite epoxy composite materials increased constantly with the aging time. Because of post-curing at UV aging primary stage, resin mechanical strength decreased first, then increased and dropped .The inter-laminar shear strength of graphite epoxy composite materials with coating dropped to 90.6%, the flexural strength dropped to 89.6% after UV aging for 15days.While the inter-laminar shear strength of graphite epoxy composite materials without coating dropped to 87.9%, the flexural strength dropped to 89%.