Role of damage in the failure of heterogeneous materials

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The proposed research program will use a state-of-the-art micro-computed tomography (microCT) facility at Queen's University, equipped with an in-chamber loading stage, to acquire 3D images of internal damage that develops as heterogeneous materials are progressively loaded to failure. Two very different classes of heterogeneous materials will be considered: steel and aluminum alloy sheet materials containing hard second-phase particles that nucleate small voids when subject to applied plastic strains, and cancellous bone tissue (i.e. the porous tissue in the ends of long bones and in vertebrae) that accumulates microcracks as a result of everyday mechanical cyclic loading. While these two materials are very different, a common investigative approach will be employed to study the role of damage in causing catastrophic failure. The research to be undertaken is fundamental in nature, focusing on key local features that govern the onset of global catastrophic material failure. However, the knowledge to be gained by this research is of use to a number of receptors. The grades of steel and aluminum alloy sheet materials to be studied are used in a number of structural applications, such as car frames and body panels in the automotive industry, where premature material failure during part manufacturing or while in service is an ongoing issue. Hence the results are of potential interest to both material fabricators and part manufacturers. For the bone research, the relationship between the structure of cancellous bone, the presence of microcracks, and the resulting fracture strength is very complex. A better understanding of this relationship would not only advance our knowledge of this poorly understood failure behaviour, but it would also lead to improvements for biomechanical technologies, such as synthetic bone scaffolds and diagnostic imaging devices. The major outcomes and impact of this research will be a better understanding of the role of damage in the failure of metal alloys and cancellous bone, with improved or new models to predict this behaviour. Highly-qualified personnel who work on this research will gain valuable skills in areas of image processing, computer coding, materials characterization (optical and scanning electron microscopy), design of mechanical fixtures and testing protocols, advanced data analysis (e.g. statistics), finite element method modelling, project management, problem solving, critical thinking, and oral presentation and technical writing skills. The study of damage in the failure of cancellous bone represents a non-traditional topic in materials science and engineering that is likely to be more attractive to women and persons from under-represented groups in this field, as well as other related disciplines, e.g. mechanical engineering.