NASA Self-Repairing Fatigue Damage in Metallic Structures for Aerospace Vehicles Using Liquid-Assisted Shape Memory Alloy Self-Healing (SMASH) Technology

A three dimensional constitutive model of SMA that describes evolution of elastic and transformation strains has been developed at Northwestern University and implemented into finite element software [1]. Recently, the model has been expanded to include plasticity contributions to deformation which enables robust calculations over a great range of thermo-mechanical loadings. Using this rigorous constitutive model, finite element simulations of the SMA-reinforced composite structures can be developed and the responses studied using ABAQUS software. For the planned work, FEA of various SMA reinforcement architectures with multi-axial orientations, ply constructions, as well as long/short fibers will be simulated to determine optimal material properties and SMA wire geometry, to maximize the self-healing property of the composite. FEA can also help reduce stress concentration and plastic deformation in the composite structures by defining ideal wire placement and interfacial conditions. Figure 2 shows a preliminary result from a finite element model of a 2D cross-section of a notched SMA composite beam. From this simulation the stress distribution and phase transformation in the SMA wires is clearly observed as well as local interfacial stresses and load transfer to the matrix material.