Additively Manufacturing Smart Cellular Materials: Self-healing Protection for Space Applications

Abstract

I will describe my research endeavours in the development of a new generation of smart cellular materials, expanding the frontiers of manufacturing engineering. The main motivation and focus are on space applications, where there is a demand for lightweight materials with significant energy absorption to mitigate against hard landings and impact from space debris. However, the research is of relevance to a wide range of sectors: e.g., automotive crashworthiness, structural defence, and civil blast protection. 

The use of cellular materials in engineering applications has been hindered due to the challenges associated with the fabrication of such complex geometries. However, these challenges can now be overcome through the use of additive manufacturing technologies, which have enabled the fabrication of geometries of significant complexity. 

In my work, I have exploited the opportunities created by additive manufacturing and explored: (1) the process-geometry-property interactions of cellular materials, and (2) the manufacturing of metallic Shape Memory Alloys (SMAs) cellular structures, which can exhibit a “self-healing” functionality through superelasticity and shape memory effect. Firstly, quasi-static and dynamic mechanical testing on stainless steel 316L cellular geometries is combined with a wide range of material characterisation techniques to understand the interplay between additive manufacturing process parameters, geometry and performance. Five cellular structures were investigated, finding that the geometry played a dominant role, relative to the Laser Powder Bed Fusion (LPBF) process parameters. Secondly, I have additively manufactured nitinol (NiTi) cellular structures that exhibit superelasticity and shape memory effect. This is considered a long-standing challenge due to the high sensitivity of nitinol’s phase transformation characteristics to composition and temperature. Two NiTi cellular structures were successfully 3D printed after a comprehensive analysis of LPBF process parameters; a diamond lattice structure and a new auxetic structure which was obtained through topology optimization. Finite element simulations, mechanical tests and a wide range of material characterization techniques were then used to understand the performance of these additively manufactured smart cellular structures. 

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