Compression property analysis of X-cor sandwich composites

X-cor sandwich, a novel composite reinforced by Z-pins of X shape, can be applied in aeronautical and astronautical fields. In this article, analytical and experimental studies are carried out to examine the out-of-plane compression properties of X-cor sandwich panel. An analytical formula of equivalent out-of-plane compression modulus is derived by investigating the three dimensional model of X-cor single cell. The compression strength of X-cor is governed by the elastic buckling of Z-pin behaving as beam-column on an Winkler elastic foundation. Therefore the cooperating effects between foam and Z-pin are explained and the compression strength is predicted, and the analytical prediction rule is consistent with measured results. By means of embedding Z-pins made from CF/Epoxy in PU and PMI foams, X-cor sandwiches are prepared. Experimental results show that the out-of-plane compression property is improved by increasing the angle between Z-pin and face sheet, Z-pin's volume fraction, diameter, restriction of their ends as well as foam property. But with Z-pin getting longer, it is easier to lose stability, and the compression strength is lower.