Pyramidal lattice truss structures with hollow trusses

A method for fabricating pyramidal lattice structures with hollow metallic trusses has been explored. A periodic diamond hole pattern sheet consisting of 304L stainless steel hollow tubes was made by an alternating collinear lay-up process followed by vacuum brazing. The array was then folded at the nodes to create a periodic pyramidal cellular metal lattice and was then bonded to face sheets by a second vacuum brazing process. The out-of-plane compression properties of this hollow truss lattice structure have been investigated and compared to a similar lattice made with the solid trusses. In both cases, the peak strength is found to be governed by inelastic truss buckling. The compressive strength of a hollow lattice with a relative density of 2.8% was approximately twice that of a solid pyramidal lattice of similar relative density. The increased strength resulted from an increase in the buckling resistance of hollow trusses because of their higher radius of gyration.