Impact Energy Absorption of Interpenetrating Phase Composites with Architected Nitinol Cellular Cores

Abstract

Interpenetrating Phase Composites (IPCs) are three-dimensional architected materials with two or more constituent phases that are continuous and interconnected. This provides improved mechanical properties to IPCs when compared to traditional composites. The use of active and functional phases, such as shape memory alloys (SMAs), has received increased attention recently. These smart alloys can undergo significant inelastic deformation that can be restored under the effect of heating or unloading, depending on loading history. One of the most widely used shape memory alloys is nitinol, which has excellent mechanical characteristics, biocompatibility, high energy absorption, and resistance to corrosion and fatigue. In this work, the energy absorption capacity of interpenetrating phase composites comprising architected nitinol shape memory alloy microstructures is investigated by means of finite element analysis (FEA) and numerical homogenization. The nitinol phase is utilized as reinforcement, whereas the second phase consists of elastoplastic aluminum. For this purpose, three different Triply Periodic Minimal Surface (TPMS) constructs: the Schwarz Primitive, the Schwarz Diamond, and the Schoen-IWP, along with spinodal cells are considered for the reinforcement phase of the IPCs. The study explores the effect of changing the impact velocity of the moving plate, and the relative density of NiTi on the energy absorption of the aforementioned IPCs. The results indicate that spinodal-based IPCs exhibited higher values of von-Mises stress under dynamic loading compared to TPMS-based IPCs. In addition, the increase of impact velocity gives a clearer representation of the strain recovery caused by the superelasticity of nitinol. Regarding specific energy dissipation, a consistent trend emerged across all structures as the impact velocity increased. With higher velocities, there was a corresponding increase in specific energy dissipation for all structures. Primitive-based IPC had the highest specific energy dissipation under different impact velocities, followed by spinodal-based IPC, diamond-based IPC, and IWP-based IPC, respectively. Furthermore, as relative density increased, there was a notable decrease in specific energy dissipation across all structures. Additionally, the order of structures based on their energy dissipation remained the same.

Date of Award	9 Jul 2024
Original language	American English
Supervisor	Wael Zaki (Supervisor)