Study on the Shape Memory Performance of 4D‐Printed Auxetic Cellular Structures with Energy Absorption Application
Mehdi Shadman, Hamed Ahmadi, Davood Rahmatabadi, Morteza Seidi
Abstract
ABSTRACT The integration of auxetic cellular structures and shape memory polymers presents a novel approach that could introduce new paradigms for the design and application of these structures across various industries. This paper aims to explore the feasibility and potential of combining these two technologies through simultaneous analysis of the mechanical properties and shape memory performance of the 4D‐printed auxetic cellular structures. The specimens were fabricated from PETG using the FDM 3D printing method and investigated in terms of energy absorption and compressive strength, as well as shape fixity ratio and shape recovery ratio for evaluating mechanical properties and shape memory characteristics. The results indicated that auxetic cellular structures can almost fully recover and maintain their mechanical properties over multiple loading cycles, thanks to the capabilities of 4D printing technology. This finding opens up possibilities for the development of reusable impact and energy absorbers, as well as personal protective gear. Furthermore, PETG's exceptional printability, shape memory effect, and formability enabled both 3D and 4D printing under high applied strain at ambient temperature (cold programming). Two effective strategies were proposed and tested to tackle the issue of low shape fixity—the only limitation of cold programming. These strategies involved increasing the applied strain to 70% and implementing a load‐holding time. Both methods proved effective, enhancing the shape fixity ratio by 16–21% while achieving a high shape recovery rate of over 95%.