A 3-D low thermal expansion lattice fabricated from Ti-6Al-4V is shown (left). The mechanical performance of the lattice unit cell under uni-axial compression is also shown. The load increases in a linear-eleastc manner until buckling of the top three struts occurs. This causes the initial sharp load drop. The second load reduction corresponds to buckling and fracture of the lower struts in the unit cell. An optimization plot is shown for lattice stiffness (as a beam). At skew angles (θ) less than 11°, the performance of the lattice is superior to the bulk material.

Auxetic lattices were fabricated from Ti-6Al-4V and stainless-steel powder (right). Specimens with constraining walls were also produced to assess the effect of boundary constraint on the auxetic behavior. Negative Poisson's ratio behavior was established under both quasi-static and impact loading under all conditions (even with the presence of thick constraining walls). Geometry optimization studies (using finite element analysis) have shown that with thin struts or small node thicknesses, such lattices are capable of absorbing over 90% of the energy of an impact.