Topic 1: Constitutive Modelling of Chemo-mechanical Phenomena in Solids
Speaker：Professor Laurence Brassart, University of Oxford
Time：Wednesday, March 13, 16:00-17:00
Venue: Room B706, Main Building, Shahe Campus
Topic 2: Coupled Degradation and Mechanics in Polymers and Gels
Speaker: Professor Laurence Brassart, University of Oxford
Time：Friday, March 15,17:00-18:00
Venue: Room C201, New Main Building, Xueyuan Road Campus
Abstract：
Hydrolysis is the main degradation pathway in many biodegradable polymers used in biomedical applications, such as orthopaedic fixtures, cardiovascular stents, and tissue engineering scaffolds. Hydrolytic degradation involves the breaking of the polymer chains, leading to a reduction in molecular weight and mass loss by diffusion of the short chains. These microstructural changes in turn impact the mechanical properties, including modulus, strength, elongation, and toughness. Accurate predictions of the microstructure evolution over long degradation times, as well as their impact on mechanical properties, is a prerequisite to accurate chemo-mechanical simulations of biodegradable devices. In this talk I will describe our recent efforts to address this question by proposing new constitutive models within a continuum thermodynamic framework coupling large deformation, mass transport and hydrolysis reaction. For hydrogels, we propose a physics-based model to describe the loss of elasticity and mass loss in crosslinked networks. Our model can successfully reproduce degradation-induced swelling reported in experiments for several model hydrogels. For degradable polyesters, such as PLA, we formulate a new model for chain scission which accounts for the degradation mechanism (random scission, end-chain scission, or a combination of both) as well as autocatalysis. The chain scission model can be coupled to elasto-viscoplasticity to simulate concurrent changes in mechanical properties. Numerical examples and comparisons to experimental data will be presented.
About the Speaker:
Laurence Brassart is an Associate Professor in the Solid Mechanics & Materials Group of the Department of Engineering Science at the University of Oxford. She received her diploma in Mechanical Engineering from the University of Louvain in Belgium in 2007, followed by a PhD in Engineering Sciences from the same university in 2011. She then successively held postdoctoral positions at Harvard University (BAEF Fellowship) and the University of Louvain (FNRS Fellowship). From 2015 to 2019, she was a Senior Lecturer in the Department of Materials Science and Engineering at Monash University in Australia. Laurence’s research focuses on the micromechanical and constitutive modelling of engineering materials, including Polymers, Composites, Soft Materials and Energy Materials. She is particularly interested in multiphysics and multiscale aspects. In 2022, Laurence was awarded a UKRI Future Leaders Fellowship focused on the chemo-mechanics of biodegradable polymers.
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