Carbon fiber epoxy composites are being used in numerous structural applications. However, fracture toughness of these composites is always less than expected. Therefore, potential of nanofillers in improving the fracture toughness of these composites, with, three different morphologies, i.e., Gr (sheet), CNT (tube) and nanodiamond (particle), in a well-connected 3D network is evaluated in this study. Both, interlaminar and intralaminar mode I fracture toughness, revealed improvement of similar to 260% and similar to 53%, respectively, with 25Gr:50CNT:25ND CF-epoxy, as compared to CF-epoxy composite. Marking a total improvement of similar to 1523% over pure epoxy on intralaminar fracture toughness. The composites were also assessed for tensile and interlaminar shear strength. An improvement of similar to 60% and similar to 16%, respectively, is noted with the addition of nanofillers. SEM analysis for delaminated and fractured surfaces revealed the toughening mechanism to be the high surface area of nanofillers, offering strong adhesion between matrix and fiber, along with improved matrix toughness.
