Structural responses of all-composite improved-pyramidal truss sandwich cores

An improved-pyramidal truss core fabricated with a hot-press molding method is presented to manufacture carbon fiber-reinforced lattice truss sandwich structures in two steps. A series of analytical and experimental studies on structural responses and failure behaviors are carried out under the out-of-plane compressive and shear loading for all-composite improved-pyramidal truss sandwich panels with two relative densities. The size effect based on unit cell scale is explored under compression due to the contribution of the introduced cross-bars. Good agreement between the predictions and measurements based on Euler buckling and fracture failure of the struts is observed in uniaxial compressive tests, while greater deviation exists in shear tests due to the occurrence of dominated node rupture. The node failure is still a key issue for the improvement of structural mechanical performances. Taking this point into consideration, an expected interlacing layer form of pyramidal truss core is proposed to achieve further improvement. Comparisons suggest that the improved structure has relative excellent comprehensive properties. All these results also indicate that much space and opportunities still remain for the improvement and development of mechanical performances, even the achievement of structural multifunctional integration.