Shape memory alloy volume fraction of pre-stretched shape memory alloy wire-reinforced composites for structural damage repair

Shape memory alloy (SMA)-reinforced composite patches not only provide non-intrusive and flexible structural damage repair like normal polymer composite patches, but are also able to enhance the repair efficiency by applying active closure stress. The active closure stress is produced by shape recovery of pre-stretched SMA wires which are embedded in the composites. This paper describes the modelling of a cracked structure repaired by SMA wire-reinforced composite patches, and further evaluates the active closure stress. The issue of debonding at the interface between SMA wires and a polymer matrix is addressed to determine the maximum pre-strain that may be applied on SMA wires before they are embedded in composites. The minimum volume fraction of SMA wires required to produce the active closure stress specified in the design is then estimated, subject to a limitation no greater than 1.