Z-pinning is a technique to insert reinforcing fibres (also called Z-pins or Z-fibres) along the Z-direction of continuous fibre-reinforced plastics. Z-pins can be made of metal or precured unidirectional composite fibres. It is designed for use within pre-preg technology; there is extensive experimental evidence that Z-pinning dramatically improves the resistance of the composite structure to delamination.
Several ways of inserting Z-pins have been developed to date. One method involves the use of an ultrasonic hammer that forces the Z-pins through the uncured preform while inducing high frequency vibrations to them. The vibrating chamfered tip of the Z-pins locally heats up and softens the resin allowing the Z-fibre to penetrate the preform with minimal disruption of the long fibres.