Dynamic Failure of Light Weight Materials and Structures

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The proposed research addresses the critical need to develop a simulation platform to predict failure of light weight automotive, aerospace and defence vehicle structures under the high strain rate conditions associated with crash events and ballistic impact. A key challenge in the adoption of these very high strength, low density or thinner materials is their lower ductility, making it critical to accurately predict the onset of failure under crash and ballistic impact conditions. This issue is exacerbated by significant levels of heat generation through plastic work during failure; thus thermal softening and adiabatic shear localization processes must be considered in predicting failure, in addition to constitutive strain rate sensitivity and microstructural damage. To address this need, the proposed program of Discovery Research will:1. Characterize and model damage evolution during high strain rate loading, focusing on advanced- and ultra-high strength steels;2. Characterize the thermal conditions associated with high strain rate failure processes, in particular shear localization, and develop models of adiabatic shear localization; 3. Implement advanced high strain rate failure criteria within finite element codes used by industry, thereby ensuring dissemination and adoption of the research outcomes.This research will utilize the extensive suite of high strain rate constitutive and fracture characterization infrastructure already in place at Waterloo, easily the largest such laboratory in an academic setting in North America, featuring new CFI-funded ultra-fast optical cameras (10 million fps) and high speed thermal cameras (90,000 fps). The new imaging infrastructure will enable high fidelity measurements of fracture processes at high rates of strain. These in situ measurements will be complemented by optical microscopy-based and tomography measurements of damage in recovered as-tested samples. Momentum-trapping fixtures within the current tensile split-Hopkinson bar allow soft recovery of samples prior to fracture, enabling characterization of damage as a function of deformation and loading conditions. State-of-art experiments will inform new models of damage and fracture under high strain rate loading. These will see application in the development of future lightweight, crashworthy vehicles, increasing occupant safety and enhancing the competitiveness of the Canadian auto, aero and defense sectors.A total of eight graduate students will be trained over the course of this Discovery Research program. These researchers will become skilled in state-of-the-art experimental and analytical techniques within the field of material response to gross plastic deformation and impact. Their recruitment within Canadian industry and academe will further enhance Canada's future competitiveness.