Studies on Fracture Features and Fracture Toughness of CFRP Composites Fabricated by Resin Infusion Technique

Fiber reinforced polymer matrix composite laminates are extensively employed in aerospace and other advanced applications owing to their desirable properties like high specific stiffness and specific strength. However, full weight saving potential of these composites has not been completely utilized because of their susceptibility to delamination failure. The delamination failures are usually considered as propagation of a crack between two adjacent layers, individually or in combination of Mode I and II loading conditions. Mode I fracture toughness studies were conducted on carbon fiber reinforced plastic (CFRP) composites fabricated by resin infusion technique. A small amount of fiber or other material runs in a direction perpendicular to the carbon fibers, with the main intention to hold the primary fibers in position. The unidirectional (UD) fabric employed in the present study contains 3–4 wt% of glass fibers as warp fibers. This configuration could influence the fracture toughness of the laminate. Hence, in the present study, interlaminar fracture studies were conducted under Mode I loading condition on resin infused UD fabric composites. The fracture surface characteristics were studied using scanning electron microscope (SEM). The studies reveal that Mode I fracture toughness initiation value is lower than the toughness values reported for neat resin and is ascribed to weak interface between fiber and matrix. The Mode I fracture propagation values are influenced by the use of warp glass fibers employed for holding the UD fibers intact in resin infused composites. This favors additional energy absorption mechanisms, such as crack detour, fiber displacement, and fracture in addition to fiber bridging. These and other aspects of the studies are discussed in the paper.