Cellular Metal Truss Core Sandwich Structures

Closed cell honeycomb core structures are widely used for sandwich panel construction. Periodic open cell tetrahedral truss core structures have recently been shown to possess weight specific properties that compete with those of honeycomb core designs. In contrast to honeycomb, the open cell topologies provide many opportunities for multifunctionality. Past approaches to miniature tetrahedral truss fabrication from metals have utilized investment casting routes. Material choices are then constrained by the need for high fluidity during casting. Strength knockdown due to casting defects has been observed. Here, we utilize a comparatively simple wrought metal based approach. The truss cores are made by deformation shaping hexagonal perforated metal sheets. They are then bonded between thin facesheets using a transient liquid phase approach. When designed to minimize bending of members within the core, a linear dependence of core modulus and strength upon relative density is anticipated. Core relative densities of less than two percent have been obtained. With this approach, low cost truss core structures can be made from a wide variety of heat-treatable wrought alloys.