Impact properties of carbon fibers-epoxy composite/aluminum laminates: effect of cryogenic and thermal aging

Carbon-reinforced aluminum laminate (CARALL) structures, by exposure to various aging conditions, were studied to examine the effect of aging on their impact properties. After 40 thermal cycles between 25 and 100 degrees C, there was improvement in impact strength of the structures with unidirectional configurations, with maximum improvement of 22.5%. Under isothermal condition (at constant temperature of 100 degrees C), a 350 min aging caused 47.7% improvement in the impact strength. By applying cryogenic cycles between - 196 and 25 degrees C, in some structures the impact strength improved after 20 cycles, whereas other structures improved after 50 cycles. The most improvement in the impact strength under cryogenic isothermal condition was about 53.5%, obtained after aging for 150 min at - 196 degrees C. It was found that fibers pull out, fracturing, and layers delamination are the mechanisms responsible for deterioration of impact strength. Whereas, lateral and longitudinal crack propagation and the plastic deformation of aluminum layers are the energy absorption mechanisms, which can improve the impact strength. [GRAPHICS] .