The effects of material

diameter and twisting state of Z–pin on the bending properties of Z–pin reinforced composite laminates were studied by three-point bending test. The results show that the flexural strength

flexural modulus and flexural strain energy of the reinforced laminates with Z–pin half thickness implantation process are significantly improved compared with the control group. The material

diameter and twisting state of Z–pin have little effect on the flexural strength

modulus and strain energy of the specimens. The reason is that the potential delamination defects at the interface X and Y of the reinforcement group expand seriously

and the delamination damage dominates the failure of the specimen in the bending process. However

the Z–pin diameter has an important influence on the failure mode of laminates. The results show that the delamination crack propagation of small diameter Z–pin reinforced specimens is serious

but the number of initiation cracks is small. The damage of specimens is mostly controlled by a single crack. The crack growth of large-diameter Z–pin reinforced specimens is relatively common

but the number of initiation cracks is more

and the specimens are mostly multi crack damaged.