Strategic Support Package: Engineering of Active Materials by Multiscale/Multiphysics Computational Mechanics

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Continuum Mechanics describes the response of solid and fluid systems subject to loading. The primary assumption of Continuum Mechanics is that matter can be viewed as a continuous distribution. This view of the world is termed macroscopic and has served the engineering community well, allowing for the virtual design of complex structures. In recent years, however, the engineering of structures at the microscopic scale has become ubiquitous. Applications include computer processors, medical devices, cellular technology, among others. As the size of components and devices decrease to the microscopic scale and beyond, so the classical continuum assumptions become less valid. That is, the discrete nature of matter starts to play a role giving rise to size effects. Classical continuum formulations do not possess a length scale and are unable to predict size effects. Thus, computer models based on these continuum formulations (typically finite element models) are of limited engineering value.Active materials - materials that change their structure when subjected to a non-mechanical field - have numerous applications in engineering, for examples, as artificial muscles or as actuators. The interaction between the material and the applied fields gives rise to a coupled problem. The research proposed here will develop formulations for coupled problems to enable the next generation of active materials with optimised macrostructural and microstructural form tailored to function. The fields to couple with the mechanical one include thermal, electric, magnetic, and chemical.To optimise the microscopic structure of a material one must have a robust and accurate continuum model that captures size effects. Linking the macroscopic and microscopic scales will be accomplished using a new class of micro-to-macro transition techniques for coupled problems - also termed computational homogenisation. The fundamental idea is to transfer information concerning the loading from the macroscopic scale down, and then to solve a problem at the microscopic scale that captures all the key features that give rise to coupling and size effects. The averaged (homogenised) response is then returned to the macroscopic scale. Following this approach, crude assumptions regarding the microscopic structure can be avoided leaded to more accurate and predictive simulations. The coupling of multiple fields across the scales is however very challenging and requires the development of new algorithms and continuum formulations. Optimisation theory allows one to design a component to maximise a certain function of interest subject to various constraints. The theory is relatively mature for engineered products at the macroscopic scale. This is not the case at the microscopic scale and certainly not the case for multiscale product design. The ability to optimally design and engineer active materials from the microscopic scale up will lead to a step-change in product functionality and design. The objective of the research is the enable this revolution through advanced algorithms and computational models.In addition to the stated scientific objectives, the research will underpin the formation of a new Centre of Excellence in Computational Engineering & Discovery. The Centre aims to promote mechanics in the UK by taking a leading role in the organisation of workshops and seminars, and through the education and development of postgraduate researchers.