Plastic Hinging Collapse of Periodic Cellular Truss Cores

Abstract

Periodic cellular metals (PCMs) have considerable potential as a new type of hybrid material for sandwich panel cores, due to their high architectural efficiency and load-bearing capability at relatively low mass. The mechanical performance of these materials is controlled by both architectural and microstructural parameters. In the case of PCM struts that have intermediate slenderness ratios, the peak load capacity is determined by the inelastic buckling stress, in which the rotation of the strut ends is opposed by their plastic hinging resistance. Strut rotation is, therefore, a key component of the overall PCM failure mechanism. In the present study, a method is developed for measuring the plastic hinging strength by allowing the truss core nodes to spread radially outward during collapse. Both finite element (FE) and experimental methods were used to study this behavior in AA3003 truss cores; the effect of work hardening, interfacial friction, and specimen size was examined. Direct measures for the plastic hinging resistance can be obtained and it was possible to demonstrate that while work hardening during PCM stretch-forming fabrication introduces significant work hardening in the near-hinge region, not all of the strengthening is available to resist plastic hinging collapse by virtue of the Bauschinger effect.