Dynamic Behaviour of Multiphase Media under High-Strain-Rate Loading

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My proposed research program investigates the dynamic response of multiphase materials under high-strain-rate loading, focusing on the role of mesoscopic variations in heterogeneity on the response of the bulk materials. This program is comprised of thrust areas pertaining to two types of multiphase materials, specifically i) foams and ii) particle-doped elastomers. The research approach will be primarily experimental, however computational investigations will complement all experimental work. The long-term objectives of the research program are summarized as: * advancing the fundamental understanding of multiphase material response under impulsive loading.* investigating and modeling multi-scale physical effects, particularly the effect of mesoscale variations on the bulk material behaviour of multiphase and multi-material systems.* develop and apply new experimental methodologies related to high-strain-rate testing of multiphase materials under impact and blast wave loading.* apply new manufacturing technologies and innovative optimization approaches to the design of materials with applications in protective equipment.* train the next generation of scientists and engineers in the area of high-strain-rate deformation.*The practical objectives of the proposed research program pertain primarily to the development of advanced materials applied to the design of protective equipment. These materials are relevant to a range of commercial applications from sporting equipment and ballistic protection to automotive and industrial safety. The multidisciplinary nature of the research plan and broad applicability ensures effective training of HQP. A summary of research efforts in the proposed thrust areas is as follows:**i) Foams are used extensively in personal and structural protective applications due to their energy absorption capabilities. In recent years, there has been an increased interest in the development of new materials to provide superior protection from a wide range of potential dangers, such as common sport-related impacts or protection from blast waves due to an explosion. The research plan is to develop a variety of property-graded foams that are optimized to reduce the levels of stress transferred to a protected body. This will be accomplished by varying the actual foam materials through the thickness of the samples as well as their density (porosity control). Producing a foam from several materials offers greater parametric variability in terms of material properties than density grading alone. The foams will be produced using additive manufacturing technologies and will be tested under quasi-static and high-strain-rate loading. The investigation focuses on the effectiveness of material grading approaches with regard to stress attenuation.**ii) Epoxies doped with hard inclusions have found applications as high-strength interstitial components. The addition of inclusions to either epoxies or elastomers at volume fractions in the range of 5-30% has been shown to result in significant strengthening of the medium in quasi-static testing. The experimental evidence suggests that a polymerized particle suspension should provide superior ballistic performance over other interstitial additives to ballistic fabrics, such as shear thickening fluids. The dynamic and failure behaviour of doped elastomers, the timescale of which has been shown to be strongly inclusion-size dependent, will be investigated at various strain rates to determine the influenced of inclusion volume fraction. The practical application of this work relates to the design of hybrid protective fabrics incorporating ceramic particles in a polymerized matrix that can provide superior ballistic, stab, and general laceration protection.