A transient liquid reactive brazing method has recently been developed that allows construction of light-weight, cellular structures from simple commercially-available, wrought, Nitinol-based elements. The new process allows the realization of a variety of sparse built-up structures, including cellular SMAs, meshes, and space frames. Unlike porous and foamed materials, the internal structure can be freely tailored to meet the needs of the application, and can be made arbitrarily light-weight. These structures retain the adaptive properties of the underlying Nitinol material (shape memory effect and superelasticity), and in sparse topologies can have an amplified form of strain recovery and improved thermal response time compared to monolithic Nitinol.
Experiments on prototype honeycomb specimens with relative density near 5% demonstrate enhanced superelasticity, and have achieved recoverable compressive strains between 30% and 70%. The thermal time response and loading rate dependence of these specimens are also demonstrated through special thermomechanical experiments. The combination of the sparse topology of a cellular solid and the adaptive properties of an SMA represents a new class of materials that can be used as light-weight passive or adaptive structural elements that respond to changes in external loads and temperature. Potential applications include reusable energy absorbing structures, highly resilient structures, light-weight armor, thermal actuation materials, vibration isolation, and biomedical implants and devices, to name a few. These materials have broad potential application in aerospace, automotive, energy, and biomedical industries.