The concept of intermittent interlaminar bonding is investigated as a means of improving the fracture toughness of cross-ply Graphite/Epoxy composites without significant loss of tensile strength and modulus. The concept of linear elastic fracture mechanies (L E F M) is used to study the effects of bonded area and bonding shape on the fracture behaviour of intermittent interlaminar bonded composites. The results indicate that the fracture toughness and notch strength of intermittent interlaminar bonded composites are improved and the tensile strength only decreased by 3-8% in comparison to those of the fully bonded composites. Damage zones around the crack tip are detected by the modified X-Ray nondestructive testing technique and the fractography. The improvement of toughness is explained based on the damage zones. The mechanisms of damage zone are shown to be caused by subcrack along the fiber on the $0^。$ ply, matrix cracking along the fiber on the $90^。$ ply, interlaminar delamination, and ply pull-out of the $0^。$ ply.
