Mechanical Performance of X-Truss/Foam Sandwich Construction

In order to improve the transverse mechanical performance of ordinary foam core sandwich, Z-pins of carbon fiber were inserted into the foam core forming a novel X-truss/foam sandwich construction. Mechanical behaviors of this new composite are mainly determined by its structure parameters, which offer many degrees of freedom to designers. Here, flatwise compression, shear, and bending tests were carried out to investigate the influence of structure parameters on mechanical behavior. These structure parameters include Z-pin inserted angle, volume fraction, and orientation of X-truss, etc. Based on the rule of mixture, equations have been derived to estimate the compression and shear properties, which conform to experimental results. With the increase of Z-pin inserted angle, compression performance is improved, while shear and bending performance decrease. The 45° angle offers the best properties of shear and bending behavior, whereas the 90° angle presents the best compression performance. In addition, using the theory of the Winkler foundation beam, a prediction equation of compression strength has been derived which indicates that larger diameter Z-pins can offer more efficient enhancement than smaller diameter ones in terms of compression behavior.