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Zahur Ullah - One of the best experts on this subject based on the ideXlab platform.
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a unified framework for the multi scale Computational Homogenisation of 3d textile composites
Composites Part B-engineering, 2019Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Edward Archer, Alistair Mcilhagger, X Y Zhou, Eileen HarkinjonesAbstract:Abstract This paper extends the applications of a novel and fully automated multi-scale Computational Homogenisation framework, originally proposed by the authors (Ullah et al. (2017)) for unidirectional and 2D-textile composites, to 3D-textile composites. 3D-textile composites offer many advantages over 2D-textile composites but their highly complicated and unpredictable post-cured geometries make their design very challenging. Accurate Computational models are therefore essential to the development of these materials. The Computational framework described in this paper possesses a variety of novel features which have never been tried for this class of composites and can potentially help to fully automatise and improve their design process. A unified approach is used to impose the representative volume element boundary conditions, which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. The Computational framework is implemented using hierarchic basis functions of arbitrary polynomial order, which allows one to increase the order of approximation without changing the finite element mesh. The yarns' principal directions, required for the transversely isotropic material model are calculated using a potential flow analysis along these yarns. This feature is very useful for 3D-textile composites and can accurately determine fibres’ directions even in the case of very deformed yarns. A numerical example from literature consisting of a 3D-orthogonal woven composite is used to demonstrate the correct implementation and performance of the developed Computational framework. Also, the developed Computational framework is used to perform a comparative study of the homogenised mechanical properties of five 3D-textile composites with different yarn architectures.
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Multi-scale Computational Homogenisation of 3D textile-based fiber reinforced polymer composites
2018Co-Authors: Zahur Ullah, Łukasz Kaczmarczyk, Edward Archer, Alistair Mcilhagger, Eileen Harkin-jonesAbstract:This paper presents a multiscale Computational Homogenisation approach for the calculation of homogenised structural level mechanical properties of 3D textile/woven based fiber reinforced polymer (FRP) composites. Textile or woven composites, in which interlaced fibres are used as reinforcement, are a class of FRP composites which provide flexibility of design and functionality and are used in many engineering applications, including ships, aircrafts, automobiles, civil structures and prosthetics [1]. The more recently developed 3D-textile composites, consisting of 3D arrangements of yarns in a polymer matrix, allow weaving of near-net-shape and complex structures as compared to the traditional 2D-textile composites. In addition, these 3D-textile composites provide high through-thickness mechanical properties, lower manufacturing cost and improved impact and delamination resistance. The macro or structural level mechanical properties of these composites are rooted in their underlying complicated and heterogeneous micro structures. The heterogeneous microstructure of these composites requires a detailed multiscale Computational Homogenisation, which results in the macroscopic constitutive behaviour based on their microscopically heterogeneous representative volume elements (RVE). Elliptical cross sections and cubic splines are used respectively to model the cross sections and paths of the yarns within these RVEs. The RVE geometry along with other input parameters, e.g. material properties and boundary conditions, are modelled in CUBIT/Trelis using a parameterised Python script. The multiscale Computational Homogenisation scheme, with a unified imposition of RVE boundary conditions, is implemented in MoFEM (Mesh Oriented Finite Element Method) [2], which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. MoFEM utilises hierarchic basis functions [3], which permits the use of arbitrary order of approximation leading to accurate results for relatively coarse meshes. The matrix and yarns within the RVEs are modelled by considering isotropic and transversely isotropic materials models respectively. The principal direction of the yarns required for the transversely isotropic material model is calculated using a Computationally inexpensive potential flow analysis along these yarns. Furthermore, the Computational framework is designed to take advantage of distributed memory high-performance computing. The implementation and performance of the Computational tool is demonstrated with a variety of 2.5D and 3D woven based FRP composites including 3D orthogonal interlock, 3D orthogonal layer-to-layer interlock, 3D orthogonal through-the-thickness angle interlock, 2.5D layer-to-layer angle interlock and 2.5D layer-layer angle interlock [4]. Keywords: Fiber reinforced polymer composites, 3D textile/woven composites, Finite element analysis, Multiscale Computational homogenization. References: [1] Z. Ullah, Ł. Kaczmarczyk, S. A. Grammatikos, M. C. Evernden and C. J. Pearce (2016). Multi-scale Computational Homogenisation to predict the long-term durability of composite structures. Computers and Structures, 181 . pp. 21- 31. [3] Ł. Kaczmarczyk, Z. Ullah, K. Lewandowski, X. Meng, X. -Y. Zhou, I. Athanasiadis, I and C. J. Pearce (2017). MoFEM-v0.6.20. Zenodo. http://doi.org/10.5281/zenodo.1053811 [3] M. Ainsworth and J. Coyle (2003). Hierarchic finite element bases on unstructured tetrahedral meshes. International Journal for Numerical Methods in Engineering, 58 (14): 2103–2130, [4] Y. Rahali, M. Assidi, I. Goda, A. Zghal, and J. F. Ganghoffer (2016). Computation of the effective mechanical properties including nonclassical moduli of 2.5 D and 3D interlocks by micromechanical approaches. Composites Part B: Engineering, 98, 194-212.
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three dimensional nonlinear micro meso mechanical response of the fibre reinforced polymer composites
arXiv: Computational Engineering Finance and Science, 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Chris J. PearceAbstract:A three-dimensional multi-scale Computational Homogenisation framework is developed for the prediction of nonlinear micro/meso-mechanical response of the fibre-reinforced polymer (FRP) composites. Two dominant damage mechanisms, i.e. matrix elasto-plastic response and fibre-matrix decohesion are considered and modelled using a non-associative pressure dependent paraboloidal yield criterion and cohesive interface elements respectively. A linear-elastic transversely isotropic material model is used to model yarns/fibres within the representative volume element (RVE). A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. The Computational model is implemented within the framework of the hierarchic finite element, which permits the use of arbitrary orders of approximation. Furthermore, the Computational framework is designed to take advantage of distributed memory high-performance computing. The accuracy and performance of the Computational framework are demonstrated with a variety of numerical examples, including unidirectional FRP composite, a composite comprising a multi-fibre and multi-layer RVE, with randomly generated fibres, and a single layered plain weave textile composite. Results are validated against the reference experimental/numerical results from the literature. The Computational framework is also used to study the effect of matrix and fibre-matrix interfaces properties on the homogenised stress-strain responses.
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multi scale Computational Homogenisation to predict the long term durability of composite structures
arXiv: Computational Engineering Finance and Science, 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Sotirios Grammatikos, Mark Evernden, C J PearceAbstract:A coupled hygro-thermo-mechanical Computational model is proposed for fibre reinforced polymers, formulated within the framework of Computational Homogenisation (CH). At each macrostructure Gauss point, constitutive matrices for thermal, moisture transport and mechanical responses are calculated from CH of the underlying representative volume element (RVE). A degradation model, developed from experimental data relating evolution of mechanical properties over time for a given exposure temperature and moisture concentration is also developed and incorporated in the proposed Computational model. A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between linear Dirichlet, uniform Neumann and periodic boundary conditions. A plain weave textile composite RVE consisting of yarns embedded in a matrix is considered in this case. Matrix and yarns are considered as isotropic and transversely isotropic materials respectively. Furthermore, the Computational framework utilises hierarchic basis functions and designed to take advantage of distributed memory high-performance computing.
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multi scale Computational Homogenisation of the fibre reinforced polymer composites including matrix damage and fibre matrix decohesion
12th World Congress on Computational Mechanics (WCCM XII), 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, C J PearceAbstract:This paper summarises the on-going work at the University of Glasgow on the Computational modelling of the hygro-mechanical behaviour of textile based fibre reinforced composite materials, including the strong coupling of the solid and moisture phases. A multiscale description is adopted and the associated implementation of the Computational Homogenisation (CH) scheme is described in detail. The ultimate goal is a multiscale modelling framework for durability assessment. CH delivers the macroscopic constitutive behaviour of the structures based on its microscopically heterogeneous representative volume element (RVE). A single layered plain weave textile composite RVE is considered, which consists of mainly two parts, i.e. yarns and matrix. Elliptical cross sections and cubic splines are used respectively to model the cross sections and paths of the yarns. The RVE geometry along with other input parameters, e.g. material properties and boundary conditions are modelled in CUBIT using a parameterised Python script. The multiscale CH scheme, with a unified imposition of RVE boundary conditions (displacement, traction and periodic) [1], is implemented in our group’s FE software MoFEM (Mesh Oriented Finite Element Method). MoFEM utilises hierarchic basis functions [2], which permits the use of arbitrary order of approximation leading to accurate results for relatively coarse meshes. The matrix and yarns within the RVE are modelled by considering isotropic and transversely isotropic materials models respectively. The principal direction of the yarns required for the transversely isotropic materials model are calculated using a Computationally inexpensive potential flow analysis along these yarns. The implementation and performance of the Computational tool is demonstrated with numerical examples.
C J Pearce - One of the best experts on this subject based on the ideXlab platform.
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multi scale Computational Homogenisation to predict the long term durability of composite structures
arXiv: Computational Engineering Finance and Science, 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Sotirios Grammatikos, Mark Evernden, C J PearceAbstract:A coupled hygro-thermo-mechanical Computational model is proposed for fibre reinforced polymers, formulated within the framework of Computational Homogenisation (CH). At each macrostructure Gauss point, constitutive matrices for thermal, moisture transport and mechanical responses are calculated from CH of the underlying representative volume element (RVE). A degradation model, developed from experimental data relating evolution of mechanical properties over time for a given exposure temperature and moisture concentration is also developed and incorporated in the proposed Computational model. A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between linear Dirichlet, uniform Neumann and periodic boundary conditions. A plain weave textile composite RVE consisting of yarns embedded in a matrix is considered in this case. Matrix and yarns are considered as isotropic and transversely isotropic materials respectively. Furthermore, the Computational framework utilises hierarchic basis functions and designed to take advantage of distributed memory high-performance computing.
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multi scale Computational Homogenisation of the fibre reinforced polymer composites including matrix damage and fibre matrix decohesion
12th World Congress on Computational Mechanics (WCCM XII), 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, C J PearceAbstract:This paper summarises the on-going work at the University of Glasgow on the Computational modelling of the hygro-mechanical behaviour of textile based fibre reinforced composite materials, including the strong coupling of the solid and moisture phases. A multiscale description is adopted and the associated implementation of the Computational Homogenisation (CH) scheme is described in detail. The ultimate goal is a multiscale modelling framework for durability assessment. CH delivers the macroscopic constitutive behaviour of the structures based on its microscopically heterogeneous representative volume element (RVE). A single layered plain weave textile composite RVE is considered, which consists of mainly two parts, i.e. yarns and matrix. Elliptical cross sections and cubic splines are used respectively to model the cross sections and paths of the yarns. The RVE geometry along with other input parameters, e.g. material properties and boundary conditions are modelled in CUBIT using a parameterised Python script. The multiscale CH scheme, with a unified imposition of RVE boundary conditions (displacement, traction and periodic) [1], is implemented in our group’s FE software MoFEM (Mesh Oriented Finite Element Method). MoFEM utilises hierarchic basis functions [2], which permits the use of arbitrary order of approximation leading to accurate results for relatively coarse meshes. The matrix and yarns within the RVE are modelled by considering isotropic and transversely isotropic materials models respectively. The principal direction of the yarns required for the transversely isotropic materials model are calculated using a Computationally inexpensive potential flow analysis along these yarns. The implementation and performance of the Computational tool is demonstrated with numerical examples.
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hierarchical finite element based multiscale Computational Homogenisation of coupled hygro mechanical analysis for fibre reinforced polymers
18th International Conference on Composite Structures (ICCS 18), 2015Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, C J PearceAbstract:This paper presents a multiscale Computational Homogenisation of the coupled hygro- mechanical analysis of the fibre-reinforced polymers (FRPs). This is ongoing research work for the development of a Computational framework to predict the long-term durability of these materials for use in the construction industry. Textile or woven composites, in which interlaced fibres are used as reinforcement, is a class of FRPs which provides full flexibility of design and functionality due to the mature textile manufacturing industry and is commonly used in many engineering applications, including ships, aircrafts, automobiles, civil structures and prosthetics [1]. During their service life textile composites are exposed to different hygrothermal environmental conditions in addition to mechanical loading, which leads to matrix plasticisation and degradation of fibres/matrix interfaces [2]. Therefore, understanding of moisture transport mechanisms and their effect on the mechanical performance of these materials are vital for predicting their long-term durability.The heterogeneous microstructure of textile composites requires a detailed multiscale Computational Homogenisation. The use of multiscale Computational Homogenisation results in the macroscopic constitutive behaviour of the structures based on its microscopically heterogeneous representative volume element (RVE). A plain weave textile composite RVE is considered in this case, consisting of matrix and yarns embedded in the matrix. These yarns are modeled with elliptical cross section and cubic spline paths. An automated parameterised RVE geometry along with material properties, boundary conditions and meshes are generated in CUBIT with Python scrip, which allows rapid generation of different types of composites.The multiscale Computational Homogenisation framework is implemented in our group’s FE software, MoFEM (Mesh Oriented Finite Element Method). A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between displacement, traction and periodic boundary conditions [3]. The effect of moisture concentration on Young’s modulus and moisture induced swelling are considered in the model. The final resultant nonlinear discretised system of equations is solved using the Newton–Raphson method. Matrix and yarns are considered as isotropic and transversely isotropic materials respectively. The required principal directions of the yarns for the transversely isotropic material model are calculated from a Computationally inexpensive potential flow analysis along these yarns. Furthermore, the Computational framework utilises the flexibility of hierarchic basis functions [2], which permits the use of arbitrary orders of approximation leading to very accurate results for relatively coarse meshes. Convergence studies based on hierarchical finite element analysis is also performed to show the effectiveness of the developed approach. The developed code is based on distributed memory parallel programming and is tested on high performance computer facilities. The implementation and performance of the developed Computational tool are demonstrated with numerical examples.
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a large strain Computational multi scale model for the dissipative behaviour of wood cell wall
Computational Materials Science, 2011Co-Authors: E Saavedra I Flores, E A De Souza Neto, C J PearceAbstract:Abstract This paper investigates the non-linear irreversible behaviour of wood cell-walls by means of a finite element-based Computational multi-scale approach. A finite strain three-scale model is proposed where the overall response of the cell-wall composite is obtained by the Computational Homogenisation of a Representative Volume Element (RVE) of cell-wall material, whose mechanical response prediction, in turn, involves the Computational Homogenisation of a cellulose core–RVE. Numerical material tests are conducted with the proposed model. The results are compared to published experimental data and demonstrate the predictive capability of the proposed model in capturing key features of cell-wall behaviour, such as viscous relaxation, recovery mechanism and hysteresis. The present results suggest a failure mechanism for the cell-wall under straining which is associated with the inelastic yielding of the amorphous portion of cellulose fibres.
Lukasz Kaczmarczyk - One of the best experts on this subject based on the ideXlab platform.
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a unified framework for the multi scale Computational Homogenisation of 3d textile composites
Composites Part B-engineering, 2019Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Edward Archer, Alistair Mcilhagger, X Y Zhou, Eileen HarkinjonesAbstract:Abstract This paper extends the applications of a novel and fully automated multi-scale Computational Homogenisation framework, originally proposed by the authors (Ullah et al. (2017)) for unidirectional and 2D-textile composites, to 3D-textile composites. 3D-textile composites offer many advantages over 2D-textile composites but their highly complicated and unpredictable post-cured geometries make their design very challenging. Accurate Computational models are therefore essential to the development of these materials. The Computational framework described in this paper possesses a variety of novel features which have never been tried for this class of composites and can potentially help to fully automatise and improve their design process. A unified approach is used to impose the representative volume element boundary conditions, which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. The Computational framework is implemented using hierarchic basis functions of arbitrary polynomial order, which allows one to increase the order of approximation without changing the finite element mesh. The yarns' principal directions, required for the transversely isotropic material model are calculated using a potential flow analysis along these yarns. This feature is very useful for 3D-textile composites and can accurately determine fibres’ directions even in the case of very deformed yarns. A numerical example from literature consisting of a 3D-orthogonal woven composite is used to demonstrate the correct implementation and performance of the developed Computational framework. Also, the developed Computational framework is used to perform a comparative study of the homogenised mechanical properties of five 3D-textile composites with different yarn architectures.
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three dimensional nonlinear micro meso mechanical response of the fibre reinforced polymer composites
arXiv: Computational Engineering Finance and Science, 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Chris J. PearceAbstract:A three-dimensional multi-scale Computational Homogenisation framework is developed for the prediction of nonlinear micro/meso-mechanical response of the fibre-reinforced polymer (FRP) composites. Two dominant damage mechanisms, i.e. matrix elasto-plastic response and fibre-matrix decohesion are considered and modelled using a non-associative pressure dependent paraboloidal yield criterion and cohesive interface elements respectively. A linear-elastic transversely isotropic material model is used to model yarns/fibres within the representative volume element (RVE). A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between linear displacement, uniform traction and periodic boundary conditions. The Computational model is implemented within the framework of the hierarchic finite element, which permits the use of arbitrary orders of approximation. Furthermore, the Computational framework is designed to take advantage of distributed memory high-performance computing. The accuracy and performance of the Computational framework are demonstrated with a variety of numerical examples, including unidirectional FRP composite, a composite comprising a multi-fibre and multi-layer RVE, with randomly generated fibres, and a single layered plain weave textile composite. Results are validated against the reference experimental/numerical results from the literature. The Computational framework is also used to study the effect of matrix and fibre-matrix interfaces properties on the homogenised stress-strain responses.
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multi scale Computational Homogenisation to predict the long term durability of composite structures
arXiv: Computational Engineering Finance and Science, 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Sotirios Grammatikos, Mark Evernden, C J PearceAbstract:A coupled hygro-thermo-mechanical Computational model is proposed for fibre reinforced polymers, formulated within the framework of Computational Homogenisation (CH). At each macrostructure Gauss point, constitutive matrices for thermal, moisture transport and mechanical responses are calculated from CH of the underlying representative volume element (RVE). A degradation model, developed from experimental data relating evolution of mechanical properties over time for a given exposure temperature and moisture concentration is also developed and incorporated in the proposed Computational model. A unified approach is used to impose the RVE boundary conditions, which allows convenient switching between linear Dirichlet, uniform Neumann and periodic boundary conditions. A plain weave textile composite RVE consisting of yarns embedded in a matrix is considered in this case. Matrix and yarns are considered as isotropic and transversely isotropic materials respectively. Furthermore, the Computational framework utilises hierarchic basis functions and designed to take advantage of distributed memory high-performance computing.
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multi scale Computational Homogenisation of the fibre reinforced polymer composites including matrix damage and fibre matrix decohesion
12th World Congress on Computational Mechanics (WCCM XII), 2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, C J PearceAbstract:This paper summarises the on-going work at the University of Glasgow on the Computational modelling of the hygro-mechanical behaviour of textile based fibre reinforced composite materials, including the strong coupling of the solid and moisture phases. A multiscale description is adopted and the associated implementation of the Computational Homogenisation (CH) scheme is described in detail. The ultimate goal is a multiscale modelling framework for durability assessment. CH delivers the macroscopic constitutive behaviour of the structures based on its microscopically heterogeneous representative volume element (RVE). A single layered plain weave textile composite RVE is considered, which consists of mainly two parts, i.e. yarns and matrix. Elliptical cross sections and cubic splines are used respectively to model the cross sections and paths of the yarns. The RVE geometry along with other input parameters, e.g. material properties and boundary conditions are modelled in CUBIT using a parameterised Python script. The multiscale CH scheme, with a unified imposition of RVE boundary conditions (displacement, traction and periodic) [1], is implemented in our group’s FE software MoFEM (Mesh Oriented Finite Element Method). MoFEM utilises hierarchic basis functions [2], which permits the use of arbitrary order of approximation leading to accurate results for relatively coarse meshes. The matrix and yarns within the RVE are modelled by considering isotropic and transversely isotropic materials models respectively. The principal direction of the yarns required for the transversely isotropic materials model are calculated using a Computationally inexpensive potential flow analysis along these yarns. The implementation and performance of the Computational tool is demonstrated with numerical examples.
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Nonlinear micro-mechanical response of the fibre-reinforced polymer composites including matrix damage and fibre-matrix decohesion
2016Co-Authors: Zahur Ullah, Lukasz Kaczmarczyk, Chris J. PearceAbstract:A three-dimensional multi-scale Computational Homogenisation framework was developed for the prediction of nonlinear micro-mechanical response of the fibre-reinforced polymer (FRP) composite. Two dominant dam- age mechanisms, i.e. matrix damage and fibre-matrix decohesion were considered and modelled using a non- associative pressure dependent thermodynamically consistent paraboloidal yield criterion and cohesive elements respectively. A linear-elastic transversely isotropic materials model was used to model yarns within the representative volume element (RVE), the principal directions for which were calculated using a potential flow analysis along these yarns. A unified approach was used to impose the RVE boundary conditions, which allows conve- nient switching between linear displacement, uniform traction and periodic boundary conditions. Furthermore, the flexibility of hierarchic basis functions and distributed memory parallel programming were fully utilised. The accuracy and performance of the developed Computational framework were demonstrated using an RVE with ran- domly distributed but periodic and axially aligned unidirectional fibres subjected to transverse tension and shear. The macro-strain versus homogenised stress responses were validated against the reference results from the liter- ature. Finally, effects of varying interfacial strength and fracture energy were studied on the homogenised stress versus macro-strain responses.
R Das - One of the best experts on this subject based on the ideXlab platform.
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Multi-scale modelling of rolling shear failure in cross-laminated timber structures by Homogenisation and cohesive zone models
International Journal of Solids and Structures, 2016Co-Authors: E. I Saavedra Flores, Kristi Saavedra, Y. Chandra, Jorge Hinojosa, R DasAbstract:In this paper we investigate the rolling shear failure in cross-laminated timber structures by Homogenisation and cohesive zone models. In order to predict the structural response, four spatial scales are interlinked within a purely kinematic multi-scale modelling framework. The constitutive description has incorporated information coming from the wood cell-wall in the order of a few nanometres, wood fibres with dimensions of tens of micrometres and growth rings described by a few millimetres. The Computational Homogenisation scheme is solved sequentially from the lowest to the highest level in order to determine the effective mechanical properties for the fourth (structural) scale represented by a cross-laminated timber plate with dimensions of the order of one meter. In order to simulate the cracking in the material, a cohesive zone model is adopted at the homogenised macroscopic scale. The finite element problem is then solved using a mixed domain decomposition strategy due to its huge number of unknowns. This approach allows us to capture interlaminar and inter-fibre cracking and to solve the macroscopic equilibrium problem using parallel computations. Our numerical predictions are compared with experimental results and are validated successfully. In particular, we study the influence of wood density, edge-gluing and span-to-depth ratio on the rolling shear failure in cross-laminated timber.
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Analysis of cross-laminated timber by Computational Homogenisation and experimental validation
Composite Structures, 2015Co-Authors: Iman Dayyani, Rafael Castro-triguero, R Das, F. Alejandro Diazdelao, Rafic M. Ajaj, P. González SotoAbstract:In this paper we investigate the mechanical behaviour of cross-laminated timber panels by a Computational Homogenisation approach. A finite element procedure is adopted within a multi-scale modelling framework to determine the constitutive response of timber. As some of the microstructural parameters of wood are either not well-known or susceptible to considerable variation, we introduce uncertainty in the definition of the material. In order to validate the present multi-scale model, we measure experimentally the longitudinal Young's modulus and density of sawn wood beams made of radiata pine. In addition, we carry out several experimental tests on cross-laminated timber panels subject to bending, shear and compression loads. Our numerical predictions are compared with the experiments and are validated successfully, revealing the potential predictive capabilities of the present multi-scale modelling for the analysis of wood materials and timber structures.
Marc G. D. Geers - One of the best experts on this subject based on the ideXlab platform.
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Wavelet based reduced order models for microstructural analyses
Computational Mechanics, 2019Co-Authors: Rody A. Tuijl, Cale Harnish, Karel Matouš, Joris J. C. Remmers, Marc G. D. GeersAbstract:This paper proposes a novel method to accurately and efficiently reduce a microstructural mechanical model using a wavelet based discretisation. The model enriches a standard reduced order modelling (ROM) approach with a wavelet representation. Although the ROM approach reduces the dimensionality of the system of equations, the Computational complexity of the integration of the weak form remains problematic. Using a sparse wavelet representation of the required integrands, the Computational cost of the assembly of the system of equations is reduced significantly. This wavelet-reduced order model (W-ROM) is applied to the mechanical equilibrium of a microstructural volume as used in a Computational Homogenisation framework. The reduction technique however is not limited to micro-scale models and can also be applied to macroscopic problems to reduce the Computational costs of the integration. For the sake of clarity, the W-ROM will be demonstrated using a one-dimensional example, providing full insight in the underlying steps taken.
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Computational Homogenisation of acoustic metafoams
European Journal of Mechanics - A Solids, 2019Co-Authors: M.a. Lewińska, V Varvara Kouznetsova, J.a.w. Van Dommelen, Marc G. D. GeersAbstract:Abstract Acoustic metafoams are novel materials recently proposed for low frequency sound attenuation. The design of their microstructure is based on the combination of standard acoustic foams with locally resonant acoustic metamaterials. This results in improved sound attenuation properties due to the interaction between viscothermal dissipation effects and the local resonance effects at the pore level. In this paper, the non-standard behaviour of such a metafoam with a complex two-phase microstructure is analysed through a multiscale approach. The macroscopic problem is described by general balance equations and at the microscopic scale a detailed representation of the microstructure is considered. The frequency dependent effective properties are used to explain the extraordinary acoustic performance. The Homogenisation approach is also validated using direct numerical simulations, showing that the Homogenisation technique is adequate in modelling both viscothermal dissipation and the local resonance effect within the metafoam microstructure.