Shape Memory Alloy Reinforced Self-Healing Metal Matrix Composites

Abstract

This paper reviews the synthesis, characterization, healing assessment, and mechanics of NiTi and other shape memory alloy (SMA)-reinforced self-healing metal matrix composites (SHMMCs). Challenges to synthesizing and characterizing the SMA-reinforced SHMMCs and the strategies followed to overcome those challenges are discussed. To design the SMA-reinforced SHMMCs, it is necessary to understand their microstructural evolution during melting and solidification. This requires the knowledge of the thermodynamics of phase diagrams and nonequilibrium solidification, which are presented in this paper for a model self-healing composite system. Healing assessment provides information about the autonomous and multicycle healing capability of synthesized SHMMCs, which ultimately determines their success. Different techniques to assess the degree of healing of SHMMCs are discussed in this paper. Strategies are explored to find the optimum volume fraction of SMA wires needed to yield the matrix and prevent damage to the SMA wires for the most effective healing. Finally, major challenges, knowledge gaps, and future research directions, including the need for autonomous and multicycle healing capability in SMA-reinforced SHMMCs, are outlined.