Session: 04-21-01: Dynamics of Advanced Functional Materials and Structures

Paper Number: 165850

Low-Speed Impact Response and Shape Memory Effect of Surface-Based Nitinol Lattices 

Shape Memory Alloys (SMAs) are a class of metallic alloys demonstrating a remarkable ability to recover their original shape after deformation, typically through thermally induced phase transformations. This functional response is known as shape memory effect (SME), which is induced upon the reversible phase transformations within the material. Apart from their shape memory properties, these alloys can also undergo relatively large deformations which can be partially or fully recovered upon unloading, unlike typical elastic materials. This functional property mostly associated with SMAs is known as superelasticity. The class of metallic alloys derived from Nickel-Titanium (NiTi) compositions is certainly the most abundant family of SMAs, as they usually display notable super-elasticity and SME, along with other functional properties making them exceptional in various industries, including but not limited to biomedical, aerospace, and electrical engineering industries. Furthermore, advancements in additive manufacturing techniques have enabled the fabrication of complex triply periodic minimal surfaces (TPMS) geometries, potentially ideal for applications requiring lightweight yet structurally integral structures, superior energy absorption and impact resistance characteristics and remarkable mechanical properties.
The current study investigates the energy absorption properties and functional behavior of additively manufactured TPMS structures fabricated from NiTi (Nitinol). The TPMS samples investigated are fabricated from a nearly equiatomic composition of Nickel and Titanium powder, via the laser bed powder fusion (LBPF) additive manufacturing technique. The low-speed impact penetration response of the Nitinol TPMS samples is therefore investigated. The low-speed impact test utilizes the weighted drop impact system Instron CEAST-9350 equipped with a 20 mm diameter hemispherical impactor and a 90 kN load cell suitable for testing Nitinol structures. The test parameters including the impact energy, dropped mass, impact elevation and impact speed are kept constants for all tested samples for consistency. Subsequently, post-impact testing, the SMA samples are tested for their functional behavior and specifically their SME upon heating. By means of reverse engineering tools, namely coordinate measuring machines (CMMs), the depth of penetration before and after the heating the samples is quantified, and the recovered depth of deformation for the specimens is characterized. The latter will give insights into the healing potential of damaged Nitinol samples upon the thermally induced phase transformations. The study will present force-time plots, force-deformation curves, and results of shape recovery tests for each of the samples. In addition, the critical description and explanation of the general trends for the dynamic behavior of such structures under moderate strain rate loading, and the localized damage and failure phenomena occurring will be presented.

Presenting Author: Mohamad Yassine Khalifa University

Presenting Author Biography: Mohamad Yassine is Ph.D. candidate pursuing his degree in Mechanical Engineering at Khalifa University, Abu Dhabi, United Arab Emirates. His research focuses on the energy absorption performance and impact response of additively manufactured architected materials and interpenetrating phase composites (IPCs). In particular, his work focuses on the dynamic response of the shape memory alloy Nitinol in metal-metal IPCs, such as Aluminum-NiTi composites. He has previously presented his work at the IMECE 2024, in the field "Dynamics of Advanced Functional Materials and Structures ".

Authors:

Mohamad Yassine Khalifa University
Fahad Almaskari Khalifa University
Wael Zaki Khalifa University