Faculty Publications
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Item Numerical investigation on the sensitivity of endplate design and gas diffusion material models in quantifying localized interface and bulk electrical resistance(Elsevier Ltd, 2021) Shinde, U.; Koorata, P.K.A localized non-intuitive relationship between electrical interface contact resistance and bulk properties such as bulk electrical resistance and permeability in the fuel cell gas diffusion layer (GDL) is reported. A numerical method is adopted to investigate contact pressure and hence the interface contact resistance at the interfaces of bipolar plate (BPP)|GDL and GDL|Polymer electrolyte membrane (PEM). The results are observed to be sensitive to GDL material models as well as endplate designs. This means, endplates designed to improve the electrical contact resistance or contact pressure at the BPP|GDL interface may not necessarily assure an improvement in bulk properties, in fact, it is observed in this study that these properties are inversely related. Further, a differential deformation in GDL along with consolidation effect is predicted with compressible version of hyperelastic material model. More importantly, it is revealed that the selection of material models plays a significant role in the deformation behaviour of the GDLs irrespective of the clamping design adopted. © 2021 Hydrogen Energy Publications LLCItem Combined influence of concentration-dependent properties, local deformation and boundary confinement on the migration of Li-ions in low-expansion electrode particle during lithiation(Elsevier Ltd, 2022) Kausthubharam, n.; Koorata, P.K.; Panchal, S.; Fraser, R.; Fowler, M.In this article, a low expansion electrode particle is investigated for mechanical stresses during lithiation with intrinsic and extrinsic factors included. The stress states are estimated with local deformation, concentration dependent properties, and external constraints. It is observed that lithiation of an unconstrained electrode particle lead to reduced concentration gradient of Li-ions with increase in stress magnitude for a case where the particle show concentration dependent stiffening response. Whereas, the constrained expansion of the same electrode particle result in reduced and elevated concentration gradient at near-field and far-field locations, respectively. Influence of charging rate is also reported wherein limiting stress (threshold limit) is observed with increasing charging rate. Further, at elevated charging rates, a drastic reduction in concentration gradient is observed at the surface of the electrode particle. © 2022 Elsevier LtdItem Deformation Mechanics of Fuel Cell Gas Diffusion Layer: Cyclic Response and Constitutive Model(Institute of Physics, 2022) Koorata, P.K.The deformation mechanics of a typical gas diffusion layer using experimental and advanced modelling technique is reported. The experimental cyclic response is observed similar to pseudo-elastic materials with highly nonlinear loading/unloading. The cyclic compressive mechanical response of gas diffusion layer (GDL) is modelled to be the outcome of cumulative changes in deformation kinematics of matrix and fiber fractions. The individual mechanisms necessitating the energy dissipation, residual strain, and stress softening during cyclic mechanical response are related to nonlinear hyperelastic matrix with the damage function and inelastic activation function at the interface of constituents. The model predicts highly nonlinear elastic loading, residual strain, hysteresis, and damage quotient associated with stress softening as a function of several cycles. The significant takeaway from this study is in terms of quantifying strength, inelastic nature of individual constituents. The proposed model is simulated for low-level altering stresses of up to twenty cycles. The results show the build-up of residual strains and hysteresis as a function of fuel cell clamping pressure. © 2022 The Electrochemical Society (“ECS”). Published on behalf of ECS by IOP Publishing Limited.