Engineering resilient hierarchical metamaterials

Metamaterials can be engineered to be multifunctional (offering combinations of properties not achievable by conventional engineering materials) and occupy regions of material property space (such as high stiffness, strength and fracture toughness at low density) that were previously empty. Recent advances in `large-area addictive manufacturing with scalability, not previously achievable by two-photon polymerization or traditional stereolithography, promise significantly reduced manufacturing time, which will speed up industrial uptake. Whilst significant recent progress had been made to understand how the principles of hierarchical design affect mechanical robustness and damage tolerance, there are also many gaps. For example, on how to suppress fracture through toughening mechanisms; reduction of structural instabilities; and, how to optimise for high toughness, yet maintain a high stiffness and strength at low density. This proposed project will focus on the ductile fracture and fatigue damage response of metamaterials. Theoretical modelling (homogenization), experiments and numerical simulations (FE) will be used to link microstructural phenomena to observable macroscopic deformation response and bulk properties. The aim is to obtain a fundamental understanding of the interactions between damage mechanisms that develop at multiple length scales, formulate theoretical methods for obtaining bounds on their properties, and provide guidelines for design with these materials.