Abstract: Through-the-thickness reinforcement of laminated composites by z-pinning has attracted more and more attention since the middles of 1990s. The insertion of z-pin, with the volume fraction of fibrous z-pin less than 5%, can lead to an up to 18-fold increase in mode I fracture resistance of the z-pinned polymer composite laminates, with a retention of 91%-98% the tensile and 100% of the compressive strengths. There is also a 50% reduction in the delamination area after the low-energy impact. Compared to the other reinforce technologies, such as weaving, knitting, braiding, and stitching, etc., z-pinning is easier to be manufactured and controlled in its quality, which has been applied to some engineering structures in aerospace industry in recent years. In this paper, the z-pinning technology is briefly described and recent advances on modelling the mechanical behaviour of z-pin is reviewed.

Key words: composite laminates, z-pinning, delamination, interlaminar improvement, delamination toughness