Ozone and water immersion effects on compression strength and fracture behavior of carbon/epoxy laminates

Compression tests were assessed to evaluate the ageing effects on carbon fiber/epoxy resin laminates exposed to ozone and water immersion. Laminates with distinct fiber arrangements (unidirectional - UD and plain weave - PW) were tested under compression strength at room (22 °C) and high (82 °C) temperatures after conditioning. The results show that the composites were mainly affected by direct exposure to water and to the high temperature used in the tests. Ozone exposure was also harmful, but to a lesser extent due to ozone attack occurring on the outer surface of the composite. The UD laminate conditioned in water immersion showed that its compressive strength, tested at room temperature, decreased around 16%. This downward trend was accentuated in tests at higher temperatures. Regarding PW laminate, exposed to water immersion and tested at room temperature, a greater reduction was observed (~23%) in compressive strength. High temperature tests also show the influence of this agent on the degradation of the composités property, with a reduction of up to 25%. Fractographic analyses confirmed that the water immersion and the high temperature used in the mechanical tests promoted the degradation of matrix and fiber/matrix interface, with the presence of interface weakening, fiber splitting, delamination, and cracks.