Titanium alloy lattice truss structures

A high-temperature forming and diffusion bonding method has been investigated for the fabrication of modified pyramidal lattice core sandwich structures from a titanium alloy. A periodic asymmetric hexagonal perforation pattern was cut into thin Ti–6Al–4V sheets which were then folded along node rows by a combination of partial low-temperature bending followed by simultaneous hot forming/diffusion bonding to form sandwich panel structures with core relative densities of 1.0–4.1%. The out-of-plane compression and in-plane longitudinal shear properties of these structures were measured and compared with analytical estimates. Premature panel failure by node shear-off fracture was observed during shear testing of some test structures. Node failures were also initiated at stress concentrations at the truss–facesheet interface. A liquid interface diffusion bonding approach has been investigated as a possible approach for reducing this stress concentration and increasing the truss–facesheet interfacial strength.