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Theoretical studies have indicated that truss core panels with a tetragonal topology support bending and compression loads at lower weight than competing concepts. The goal of this study is to validate this prediction by implementing an experimental protocol that probes the key mechanical characteristics while addressing node eccentricity and structural robustness. For this purpose, panels have been fabricated from a beryllium-copper alloy using a rapid prototyping approach and investment casting. Measurements were performed on these panels in flexure, shear and compression. Numerical simulations were conducted for these same configurations. The measurements reveal complete consistency with the stiffness and limit load predictions, as well as providing a vivid illustration of asymmetric structural responses that arises because the bending behavior of optimized panels is dependent on truss orientation. Ó

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Light metal sandwich panel structures with cellular cores have attracted interest for multifunctional applications which exploit their high bend strength and impact energy absorption. This concept has been explored here using a model 6061-T6 aluminium alloy system fabricated by friction stir weld joining extruded sandwich panels with a triangular corrugated core. Micro-hardness and miniature tensile coupon testing revealed that friction stir welding reduced the strength and ductility in the welds and a narrow heat affected zone on either side of the weld by approximately 30%. Square, edge clamped sandwich panels and solid plates of equal mass per unit area were subjected to localized impulsive loading by the impact of explosively accelerated, water saturated, sand shells. The hydrodynamic load and impulse applied by the sand were gradually increased by reducing the stand-off distance between the test charge and panel surfaces. The sandwich panels suffered global bending and stretching, and localized core crushing. As the pressure applied by the sand increased, face sheet fracture by a combination of tensile stretching and shear-off occurred first at the two clamped edges of the panels that were parallel with the corrugation and weld direction. The plane of these fractures always lay within the heat affected zone of the longitudinal welds. For the most intensively loaded panels additional cracks occurred at the other clamped boundaries and in the center of the panel. To investigate the dynamic deformation and fracture processes, a particle-based method has been used to simulate the impulsive loading of the panels. This has been combined with a finite element analysis utilizing a modified Johnson-Cook constitutive relation and a Cockcroft-Latham fracture criterion that accounted for local variation in material properties. The fully coupled simulation approach enabled the relationships between the soil-explosive test charge design, panel geometry, spatially varying material properties and the panel's deformation and dynamic failure responses to be explored. This comprehensive study reveals the existence of a strong instability in the loading that results from changes in sand particle reflection during dynamic evolution of the panel's surface topology. Significant fluid structure interaction effects are also discovered at the sample sides and corners due to changes of the sand reflection angle by the edge clamping system. 2