Evaluating Z-pin performance under high-velocity impact conditions

High-performance aerospace composite structures manufactured from pre-impregnated carbon fibre preforms are highly susceptible to delamination failure in the event of high-velocity impact. An established solution to this problem is to insert Z-pins into the composite structure to enhance through-thickness impact performance. This practice is known as through-thickness reinforcement (TTR). The production and impact testing of full-scale and sub-scale components is expensive and does not yield a suitable environment for the analysis of Z-pin behaviour and effects under the observed complex loading conditions. By contrast, prior small test scales and low strain-rates have not been sufficient to invoke the large-scale bridging action of Z-pins or study their behaviour at strain-rates representative of a real impact event. This study presents a test method which has been designed, using finite element analysis, to be capable of reproducing delamination failure at sub-element scale and high strain-rate using soft-body impact. This test makes use of a simple cantilevered tapered plate which is subjected to impact by a gelatine projectile using a gas-gun. This method will recreate the delamination failure mode observed under high-velocity impact at substantially reduced cost and provide a test-bed for assessing Z-pin performance at larger scales