Z-pin Reinforcement on the Core Shear Properties of Polymer Foam Sandwich Composites

The influence of orientation of carbon fiber rods on the core shear properties of Z-pins reinforced foam core sandwich was investigated by a series of out-of-plane shear tests. The reinforcing pins were aligned along or opposite to the shear loading direction, or they were arrayed in an X-shaped configuration. Experimental results indicate that the compression pin and the tension pin have an equivalent contribution to core shear stiffness when they are arrayed opposite to each other. Pull-out of Z-pins from facesheets and foam core can absorb strain energy after debonding and hinder crack extension. Two shear failure modes were observed in the tests, and analytical formulae predicting the shear strength have been presented.