Current status and future research imperatives of self-healing metal matrix composites

Self-healing Metal Matrix Composites (SHMMCs) have emerged as an important field of research in materials engineering. This paper critically examines the current state of the art of SHMMCs, including matrix alloys, reinforcements, crack orientation, and stress states under which self-healing has been studied. The significance of characteristics of SMA reinforcement, including size, length, distribution, and interface strength, is presented. Challenges in synthesizing SHMMCs, including achieving wetting, bonding, and load transfer between the metal matrix and the reinforcement, overcoming the problem due to oxidation, and irregularities of cracked surfaces, are discussed. Needs of future research directions are outlined, including examining thermodynamics and kinetics of self-healing, design of microstructure based on mechanics for targeted self-healing, and developing capabilities of autonomous and capacity for multicycle healing in metals, especially in high temperatures metals and alloys. The need for developing self-healing and shape-changing capabilities in man-made materials similar to biological living materials is discussed.