Experimental study on z-pin bridging law by pull-out tests

This paper presents an experimental study on the zpin bridging law. The relationship between the z-pin bridging force and its displacement was measured by z-pin pull-out tests. Three types of samples were examined, which included single small pin; 3·3- small-pin (three columns×three rows) and 3·3-bigpin samples. For 3·3-small-pin samples, a typical pull-out curve with initial elastic bonding, unstable debonding and frictional sliding was obtained. A high peak value of the debonding force was reached before z-pin debonding started. After debonding was initiated, the pull-out force dropped rapidly to a lower value, the pins were then pulled out steadily. The difference between the peak debonding force and the frictional pull-out force decreased with increasing loading rate. However, for samples with big pins, it was difficult to discern the peak debonding force.