Embedded magnetic shape memory sensory particles in lightweight composites for crack detection

Abstract

Through embedding functional materials into structural components, smart composites offer an alternative to structural health monitoring (SHM). The present work focuses on the development of a new kind of composite with metamagnetic shape memory alloy (MMSMA) particles as the sensory particle reinforcements. The premise of this approach is that sensory particles can experience martensitic transformation (MT) in the presence of the crack tip stress field, emitting acoustic signals and changing their magnetic state upon the transformation, which can be exploited using acoustic and/or magnetic sensors to detect the crack location. The composite fabrication consisted of the consolidation of pure Al and Ni43Co7Mn39Sn11 MMSMA powders through spark plasma sintering at 400 °C and 560 °C. Consolidation at 400 °C yielded a porous composite. Consolidation at 560 °C yielded a highly dense composite with a diffusion region between the particles and matrix consisting of Al-Mn-Ni rich and Sn-Mn rich zones. Thermomagnetic testing of this composite displayed a similar response to the standalone Ni43Co7Mn39Sn11 powder indicating that the particles can still transform after the composite fabrication. Fatigue crack testing of the composite revealed particles in the presence of cracks undergoing MT. This demonstrates the feasibility of the sensory magnetic particle approach as a potential new SHM technique, however, the interface should be further engineered to optimize the load transfer from matrix to the particles.