NUMERICAL PREDICTION OF THE EFFECTIVE MECHANICAL BEHAVIOR OF INTERPENETRATING PHASE COMPOSITES COMPRISING ARCHITECTED NITINOL CORES

This work focuses on the computational investigation of 3D interpenetrating phase composites ( IPCs) consisting of an architected shape memory alloy (SMA) microstructure embedded in an elastic-plastic second phase. The SMA functional phase consists of Nitinol (NiTi) for which the constitutive material behavior is simulated using a user-defined material subroutine (UMAT) in Abaqus finite element software. Beam-based and mathematically driven triply periodic minimal surfaces (TPMS) architectures are considered for the NiTi functional phase. IPC unit cells are identified and modeled considering idealized periodic boundary conditions (PBCs). The mechanical and functional properties of the unit cells are evaluated using volumetric homogenization. The effective mechanical response is evaluated and analyzed as a function of NiTi volume fraction considering various loading conditions. The results show that NiTi morphology significantly affects the elastic stiffness, which varies monotonically with NiTi content. Among the geometries considered for the NiTi cores, TPMS cores having a Schwarz Diamond topology resulted in the highest effective axial stiffness and bulk moduli, whereas TPMS IWP topologies resulted in the highest strain recovery.