Deformation and Failure of Mechanically Adaptive Cellular Materials

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Man-made structures with a significant load-bearing function require laborious and costly design efforts in order to ensure safe and efficient performance. In contrast, load-bearing structures found in the natural world evolve and grow into suitable configurations because they are composed of adaptive materials, such as bone and wood, that self-configure according to the mechanical loads they carry. Familiar examples of this mechanical adaptability are the higher bone density observed in the heavily loaded racket-arm of tennis players, the loss of bone mass in astronauts due to a low gravity environment, or variation in annual tree ring thicknesses that reflect environmental stress. As a result of mechanical adaptability to the external environment, bone and wood exhibit excellent load-carrying capacity, are lightweight, and require little in the way of resources to produce (i.e. little energy and raw materials) relative to synthetic materials. This project will evaluate a bio-inspired strategy for fabricating synthetic materials that adapt to their mechanical environment. The strategy will employ a nano-fabrication technique to deposit a structurally robust nanocomposite coating onto a porous foam substrate. Under appropriate processing conditions, it is hypothesised that thicker coatings can be deposited in regions experiencing higher loading, resulting in adaptive nanocomposite-coated foams with mechanically tailored microstructures. A program of testing will be conducted in order to establish the mechanical behaviour and properties of these materials, which will play an integral role in establishing the interrelationship between the processing, structure, and properties of uniform and adaptive foams. The results will enable an assessment of the mechanical adaptability of nanocomposite-coated foams, and the suitability of these materials for anticipated engineering applications. Theoretical predictions and preliminary results suggest a combination of exceptional mechanical properties (e.g. strength and stiffness) with high porosity, low density, and multi-functionality is achievable, making these materials excellent candidates for use as artificial tissue scaffolds in biomedical applications, and as lightweight load-bearing materials in weight-critical structures.