Development and Deformation Characteristics of Nitinol Based Single-Layer Fibre Network

Three-dimensional metallic fibre network materials are of recent research interest owing to their tunable properties that potentially could cater to wide-range application domains. In general, single-layer fibre network is the basic unit of such multi-layered three-dimensional fibre network designed considering stochastic or ordered arrangement of metallic fibres with voids between them inducing porosity. In the present study, single-layer fibre network is developed using equiatomic Nitinol fibre (125 µm diameter). Prior to this, Nitinol fibres were partially annealed at temperatures in the range of 400–600 °C for 1 h. Annealed fibres were evaluated for the phases (austenite and/or martensite and/or R-phase) formed and respective transformation temperatures as well as their mechanical and superelastic properties. Considering the optimally annealed (450 °C for 1 h) Nitinol fibre, the effect of fibre inclination angle in the range of 0°–45° was further investigated. It is observed that the plateau and fracture stress, and superelastic recovery strain decreases with increase in inclination angle. Further, considering the optimally annealed Nitinol fibres, a single-layer fibre network, with three 45° inclined fibres placed over two vertical fibres arrangement, was developed, which exhibits higher strain to fracture, lower plateau and failure stress, and superelastic recovery strain than Nitinol single fibre.