Integration of structural health monitoring in shape memory alloy reinforced self-healing matrix composites using piezoelectric transducers

Abstract

Integrating self-healing materials with structural health monitoring (SHM) represents a significant advancement in materials science and engineering. In applications such as aerospace, self-healing composites with SHM can detect and repair damage autonomously, enhancing safety and reducing maintenance time, which significantly improves structural durability by maintaining integrity and extending material service life. This research employs an experimental approach to validate the self-healing process of self-healing metal matrix composites reinforced with shape memory alloy fibers, by utilizing lead zirconate titanate (PZT) piezoelectric transducers mounted on the surface of the composite. A three-point bending test is used to induce damage in the metal matrix composites by applying a load at its midpoint while supporting it at both ends; then, self-healing is used to return the specimen to its original state. The ultrasonic signals from the PZT sensor were compared at three stages: pristine state, during bending (i.e., damage), and after the healing process, to evaluate the effectiveness of the healing process and health monitoring technique adopted for this study. Real-time monitoring using digital image correlation, laser profilometry, and mechanical testing was used to validate the damaged/healed signal state—demonstrated by improved recovered signal amplitude, reduced scatter energy, a notable decrease in damage indices root-mean-square deviation, normalized scatter energy, and stabilized wave propagation. The successful self-healing composite design and health monitoring results confirm the restoration of the specimen, which regained 84% of its initial shape deformation at 135 °C for 30 min (i.e., during the first step of healing). Complete shape restoration was achieved by raising the temperature to 150 °C for 90 min (during the second step of healing), recovering approximately 96% of the original flexural strength after healing.