Effect of z-pin surface treatment on delamination and debonding properties of z-pinned composite laminates

The effect of z-pin surface treatment on the delamination fracture properties of z-pinned unidirectional carbon fibre/epoxy prepreg laminate is presented in this paper. Cryogenic and plasma treatments were used to increase the pin/composite interface properties. Z-pin pullout tests were carried out to study the relations between the bridging force and the displacement. Mode-I double-cantilever beam tests were used to characterize the improvements in delamination toughness. It was pointed out that appropriate treatments could effectively increase the delamination fracture properties. Oxygen-containing functional groups could be induced on the pin surface through cold plasma treatment. An increasing surface energy is improving the wettability so that more chemical reactions can be generated between the epoxy group and z-pin surface. Furthermore, the surface roughness of z-pins can be extended with a plasma or cryogenic treatment. The pins obtained a larger surface area, which could wet by the epoxy matrix during the z-pin-insertion and curing process.