Effect of phase on debond strength in shape memory alloy reinforced composites

•Single fiber pullout tests performed to decouple modulus and.•transformation effects.•Evaluation of martensitic and austenitic NiTi SMA embedded epoxy.•composites.•Austenite phase induced higher debond loads than martensite phase.•Debond behavior likely due to Poisson’s ratio differences between SMA phases.

Systematic single fiber pullout tests were performed on epoxy composites embedded with nickel titanium shape memory alloy (SMA) wires. The SMA wires were tested in the austenitic or martensitic states to study and decouple the elastic moduli from martensite transformation or reorientation stresses in the analysis of debond loads. The results reveal that the SMA wires that were in the austenite phase consistently produced higher debond loads as compared to that of those wires that started in the martensite phase, likely due to differences in the Poisson’s ratio. Additionally, there appears to be a relationship between the elastic modulus and debond load where reinforcements with a higher elastic modulus displayed lower debond loads. Lastly, for SMA reinforcements that underwent a martensitic phase transformation or reorientation, the debond load was equivalent to the martensite transformation or reorientation load. The results of this work illustrate the sensitivity of SMA reinforced composites on the mechanical behavior and phase transformation characteristics of the constituent materials.