Mechanical behavior and energy dissipation of infilled, composite Ti-6Al-4V trusses

Trusses are open, three-dimensional structures with repeatable unit cells useful for high-specific strength, stiffness, and energy-dissipating applications. By infilling Ti-6Al-4V trusses with an incompressible elastomer (polydimethylsiloxane) or compressible foam (polyurethane), we demonstrate non-porous composite materials with controlled mechanical properties. The advantages of infilled composite trusses include corrosion resistance, density- or strength-matching, and the creation of a continuous external surface that can enable surface properties such as resistance to aerodynamic pressure and biomedical compatibility. Flexural and compressive testing of composite trusses show reproducible behavior dominated by the underlying truss in elastic and plastic regimes. Compared to unfilled trusses, those filled with an incompressible elastomer or compressible foam delay initial compressive failure to higher strains. For all investigated energy dissipation metrics, foam-infilled trusses demonstrated equivalent or improved performance compared to unfilled ones. This included plateau stress, volumetric energy dissipation (+19%), and energy absorption efficiency (+12%) and ideality (+20%). For the highest tested truss relative density (ρ^∗ = 0.43), 150% improvement in volumetric energy absorption was observed. Compressive loading of the incompressible siloxane-filled trusses yielded higher peak failure stresses but at reduced energy dissipation. Composite trusses can therefore serve as structural solutions to improving energy absorption in higher stress applications with minimal increases to density.