Environmental Degradation of Carbon Fibre-Reinforced Epoxy Composites: An Experimental Investigation

Work presented herein investigates the chemically-induced degradation of a carbon-fibre reinforced epoxy. Monolithic coupons were conditioned from either single-sided exposure to, or complete immersion in one of five fluids; turbine oil, hydraulic fluid, ethylene glycol, deionized water or ocean water. At predefined intervals, coupons were removed from conditioning; subjected to evaluation of mass, dimensions and hardness; and destructively tested, analyzing either flexural properties or short beam strength. Secondary testing, including microscopy, x-ray micro-computed tomography and thermal analysis, was performed to further characterize degradation.It was demonstrated that significant mechanical and physical degradation resulted from exposure to deionized and ocean water, but not from exposure to hydraulic fluid, turbine oil, or ethylene glycol. Water uptake, as evaluated by sample mass change, was non-Fickian and caused a measurable loss of constituent material. This was predicted to be due to water's polarity, allowing it to disrupt both epoxy's intermolecular and intramolecular bond structure.