| 1. |
- Carlstedt, David, 1984, et al.
(författare)
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Electro-chemo-mechanically coupled computational modelling of structural batteries
- 2020
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Ingår i: Multifunctional Materials. - : IOP Publishing. - 2399-7532. ; 3:4
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Tidskriftsartikel (refereegranskat)abstract
- Structural batteries are multifunctional composites that combine load-bearing capacity with electro-chemical energy storage capability. The laminated architecture is considered in this paper, whereby restriction is made to a so called half-cell in order to focus on the main characteristics and provide a computational tool for future parameter studies. A thermodynamically consistent modelling approach is exploited for the relevant electro-chemo-mechanical system. We consider effects of lithium insertion in the carbon fibres, leading to insertion strains, while assuming transverse isotropy. Further, stress-assisted ionic transport is accounted for in addition to standard diffusion and migration. The relevant space-variational problems that result from time discretisation are established and evaluated in some detail. The proposed model framework is applied to a generic/idealized material representation to demonstrate its functionality and the importance of accounting for the electro-chemo-mechanical coupling effects. As a proof of concept, the numerical studies reveal that it is vital to account for two-way coupling in order to predict the multifunctional (i.e. combined electro-chemo-mechanical) performance of structural batteries.
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| 2. |
- Carlstedt, David, 1984, et al.
(författare)
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Unit cells for multiphysics modelling of structural battery composites
- 2019
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Ingår i: ICCM International Conferences on Composite Materials.
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Konferensbidrag (refereegranskat)abstract
- To predict the multifunctional performance of structural battery composites, multiple physical phenomena need to be studied simultaneously. Hence, multiphysics models are needed to evaluate the complete performance of this composite material. In this study the coupled analysis for multiphysics modelling of structural battery composites is presented and modelling strategies and unit cell designs are discussed with respect to the different physical models. Furthermore, FE-models are setup in the commercial Finite Element (FE) software COMSOL to study if existing physics-based modelling techniques and homogenization schemes for conventional lithium ion batteries can be used to describe the electrochemical behaviour of structural battery composites. To predict the microscopic behaviour, the local variation of the mass and charge concentrations need to be accounted for. Hence, refined models with appropriate boundary conditions are needed to capture the microscopic conditions inside the material. The numerical results demonstrate that conventional physics-based 1D battery models and homogenization schemes based on porous media theory can be used to predict the macroscopic electrical behaviour of the fibrous structural battery. For future work electrochemical experiments on battery cell level are planned to validate the numerical results.
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| 3. |
- Jänicke, Ralf, 1980, et al.
(författare)
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Identification of viscoelastic properties from numerical model reduction of pressure diffusion in fluid-saturated porous rock with fractures
- 2019
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 63:1, s. 49-67
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Tidskriftsartikel (refereegranskat)abstract
- This paper deals with the computational homogenization and numerical model reduction of deformation driven pressure diffusion in fractured porous rock. Exposed to seismic waves, the heterogeneity of the material leads to local fluid pressure gradients which are equilibrated via pressure diffusion. However, a macroscopic observer is not able to measure the diffusion process directly but senses the intrinsic attenuation of an apparently monophasic viscoelastic solid. The aim of this paper is to establish a reliable, yet numerically efficient, computational homogenization method to identify the viscoelastic properties of the macroscopic substitute model. Inspired by the Nonuniform Transformation Field Analysis, we incorporate a Numerical Model Reduction procedure. The proposed method is validated for several scenarios ranging from pressure diffusion in an unfractured poroelastic matrix, via localized pressure diffusion in interconnected fractures embedded in an impermeable matrix, to the fully coupled pressure diffusion both in fractures and the embedding poroelastic matrix.
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| 4. |
- Carlstedt, David, 1984, et al.
(författare)
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Computational modelling of structural batteries accounting for stress-assisted convection in the electrolyte
- 2022
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 238
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Tidskriftsartikel (refereegranskat)abstract
- Structural batteries consist of carbon fibres embedded in a porous structural battery electrolyte (SBE), which is composed of two continuous phases: a solid polymer skeleton and a liquid electrolyte containing Li-salt. In this paper we elaborate on a computational modelling framework to study the electro-chemo-mechanical properties of such structural batteries while accounting for the combined action from migration as well as stress-assisted diffusion and convection in the electrolyte. Further, we consider effects of lithium insertion in the carbon fibres, leading to insertion strains. The focus is placed on how the convective contribution to the mass transport within the SBE affects the general electro-chemo-mechanical properties. The numerical results indicate that the convective contribution has only minor influence on the multifunctional performance when the mechanical loading is caused by constrained deformation of constituents during electro-chemical cycling. However, in the case of externally applied mechanical loading that causes severe deformation of the SBE, or when large current pulses are applied, the convective contribution has noticeable influence on the electro-chemical performance. In addition, it is shown that the porosity of the SBE, which affects the effective stiffness as well as the mobility and permeability, has significant influence on the combined mechanical and electro-chemical performance.
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| 5. |
- Carlstedt, David, 1984, et al.
(författare)
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Experimental and computational characterization of carbon fibre based structural battery electrode laminae
- 2022
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Ingår i: Composites Science and Technology. - : Elsevier BV. - 0266-3538. ; 220
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, electrode laminae consisting of carbon fibres embedded in structural battery electrolyte (CF-SBE electrodes) are characterized with respect to their multifunctional (i.e. combined electrochemical and mechanical) performance utilizing experimental and numerical techniques. The studied material is made from commercially available polyacrylonitrile (PAN)-based carbon fibres and a porous SBE matrix/electrolyte, which is composed of two continuous phases: a solid polymer skeleton (vinyl ester-based) and a Li-salt containing liquid electrolyte. Experimental and numerical studies are performed on CF-SBE electrode half-cells, whereby a coupled electro-chemo-mechanical finite element model is exploited. Results show that, similar to traditional batteries, electrode thickness, transport properties of the electrolyte and applied current significantly affect electrochemical performance. For example, increasing the electrode thickness of the studied CF-SBE electrode from 50 μm to 200 μm results in a reduction in specific capacity of approximately 70/95% for an applied current of 30/120 mA g? 1 of fibres, respectively. Further, Li-insertion induced longitudinal expansion of carbon fibre electrodesare video microscopically recorded during charge/discharge conditions. In liquid electrolyte the total/reversible longitudinal expansion are found to be 0.85/0.8% while for the CF-SBE electrode the reversible expansion is found to be 0.6%. The fibre expansion in the CF-SBE electrode gives rise to residual strains which is demonstrated numerically. We expect that the utilized computational framework and experimental data open a route to develop high-performing, both mechanically and electrochemically, carbon fibre based battery electrode laminae for future lightweight structural components with energy storage ability.
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| 6. |
- Carlstedt, David, 1984, et al.
(författare)
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Variationally consistent modeling of a sensor-actuator based on shape-morphing from electro-chemical–mechanical interactions
- 2023
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Ingår i: Journal of the Mechanics and Physics of Solids. - 0022-5096. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- This paper concerns the computational modeling of a class of carbon fiber composites, known as shape-morphing and strain-sensing composites. The actuating and sensing performance of such (smart) materials is achieved by the interplay between electrochemistry and mechanics, in particular the ability of carbon fibers to (de)intercalate Li-ions repeatedly. We focus on the actuation and sensing properties of a beam in conjunction with the appropriate “through-the-thickness” properties. Thus, the electro-chemo-mechanical analysis is essentially two-dimensional, and it is possible to rely heavily on the results in Carlstedt et al. (2020). More specifically, the cross-sectional design is composed of two electrodes, consisting of (partly) lithiated carbon fibers embedded in structural battery electrolyte (SBE), on either side of a separator. As a result, the modeling is hierarchical in the sense that (macroscale) beam action is combined with electro-chemo-mechanical interaction along the beam. The setup is able to work as sensor or actuator depending on the choice of control (and response) variables. Although quite idealized, this design allows for a qualitative investigation. In this paper we demonstrate the capability of the developed framework to simulate both the actuator and sensor modes. As proof of concept, we show that both modes of functionality can be captured using the developed framework. For the actuator mode, the predicted deformation is found to be in close agreement with experimental data. Further, the sensor-mode is found to agree with experimental data available in the literature.
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| 7. |
- Ekre, Fredrik, 1992, et al.
(författare)
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A posteriori error estimation for numerical model reduction in computational homogenization of porous media
- 2020
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Ingår i: International Journal for Numerical Methods in Engineering. - : Wiley. - 0029-5981 .- 1097-0207. ; 121:23, s. 5350-5380
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Tidskriftsartikel (refereegranskat)abstract
- Numerical model reduction is adopted for solving the microscale problem that arizes from computational homogenization of a model problem of porous media with displacement and pressure as unknown fields. A reduced basis is obtained for the pressure field using (i) spectral decomposition (SD) and (ii) proper orthogonal decomposition (POD). This strategy has been used in previous work—the main contribution of this article is the extension with an a posteriori estimator for assessing the error in (i) energy norm and in (ii) a given quantity of interest. The error estimator builds on previous work by the authors; the novelty presented in this article is the generalization of the estimator to a coupled problem, and, more importantly, to accommodate the estimator for a POD basis rather than the SD basis. Guaranteed, fully computable and low-cost bounds are derived and the performance of the error estimates is demonstrated via numerical results.
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| 8. |
- Ekre, Fredrik, 1992, et al.
(författare)
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Combining spectral and POD modes to improve error estimation of numerical model reduction for porous media
- 2022
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Ingår i: Computational Mechanics. - : Springer Science and Business Media LLC. - 1432-0924 .- 0178-7675. ; 69:3, s. 767-786
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Tidskriftsartikel (refereegranskat)abstract
- Numerical model reduction (NMR) is used to solve the microscale problem that arises from computational homogenization of a model problem of porous media with displacement and pressure as unknown fields. The reduction technique and an associated error estimator for the NMR error have been presented in prior work, where both spectral decomposition (SD) and proper orthogonal decomposition (POD) were used to construct the reduced basis. It was shown that the POD basis performs better w.r.t. minimizing the residual, but the SD basis has some advantageous properties for the estimator. Since it is the estimated error that will govern the error control, the most efficient procedure is the one that results in the lowest error bound. The main contribution of this paper is further development of the previous work with a proposed combined basis constructed using both SD and POD modes together with an adaptive mode selection strategy. The performance of the combined basis is compared to (i) the pure SD basis and (ii) the pure POD basis via numerical examples. The examples show that it is possible to find a combination of SD/POD modes which is improved, i.e. it yields a smaller estimate, compared to the cases of pure SD or pure POD.
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| 9. |
- Ekre, Fredrik, 1992, et al.
(författare)
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Efficient Two-Scale Modeling of Porous Media Using NumericalModel Reduction with Fully Computable Error Bounds
- 2022
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Ingår i: Current Trends and Open Problems in Computational Mechanics. - Cham : Springer International Publishing. ; , s. 121-129
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The microscale problem arizing from computational homogenization of porous media problems is solved by adopting the concept of Numerical Model Reduction. Thereby, the displacement and pore pressure are the unknown fields. A suitable reduced basis is constructed for the pore pressure approximation using Proper Orthogonal Decomposition (POD), whereby it is possible to compute the appropriate basis for the displacement field in the spirit of Nonlinear Transformation Field Analysis (NTFA). Inexpensive fully computable error bounds are obtainable, and the performance of the error estimates is illustrated in this paper.
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| 10. |
- Ekre, Fredrik, 1992, et al.
(författare)
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On error controlled numerical model reduction in FE2-analysis of transient heat flow
- 2019
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Ingår i: International Journal for Numerical Methods in Engineering. - : Wiley. - 0029-5981 .- 1097-0207. ; 119:1, s. 38-73
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Tidskriftsartikel (refereegranskat)abstract
- Numerical model reduction is exploited for solving the two-scale problem that arises from the computational homogenization of a model problem of transient heat flow. Since the problem is linear, an orthogonal basis is obtained via the method of spectral decomposition. A key feature is the construction of a symmetrized version of the space-time variational format, by which it is possible to estimate the error from the model reduction in (i) energy norm and in (ii) a given quantity of interest. In previous work by the authors, this strategy has been applied to the solution of an individual representative volume element problem, whereas the error transport to the macroscale problem in the finite element squared (FE2) approach was ignored. In this paper, such transport of error is included in the error estimate. It is remarkable that it is (still) possible to obtain guaranteed bounds on the error, as compared to the fully resolved discrete finite element problem, while using only the reduced basis and with minor extra computational effort. The performance of the error estimates is demonstrated via numerical results, whereby the subscale is modeled in three dimensions, whereas the macroscale problem is either one or two dimensional.
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