Impact and residual after impact properties of carbon fiber/epoxy composites modified with carbon nanotubes

The effect of carbon nanotubes (CNTs) on the impact and after impact performance of woven carbon fiber/epoxy composites is investigated. Three nano-reinforced epoxy systems that differ in the CNT dispersion and functionalization are used as a matrix material. The composites are tested for the resistance to an out-of-plane low velocity impact, the residual compressive strength, the mode II interlaminar fracture toughness and the interlaminar shear strength. The composite with the highest mode II fracture toughness is found to be the best performing system in the compression test. The resin in this composite contains a network-like structure of CNTs. Nanotubes are found to have a dual effect on composite properties: (1) they improve the mode II interlaminar fracture toughness and (with it) damage tolerance of a composite, but (2) they also make composites more susceptible to the onset of matrix cracks leading to a larger delamination area after impact.