| 1. |
- Auenhammer, Robert, 1991, et al.
(författare)
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Sub-voxel based finite element modelling of fibre-reinforced composites
- 2024
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Ingår i: Software Impacts. - 2665-9638. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- For fibre-reinforced composites, most of their mechanical properties is tied to the fibre scale. Thus, imaging-based characterisation demands resolving fibres to characterise these materials accurately. However, high resolutions limit the field of view and lead to lengthy acquisition times. Emerging non-destructive imaging technologies and algorithms now accurately provide fibre orientations without detecting individual fibres. Studies show that voxel sizes up to fifteen times the fibre diameter are feasible, still allowing accurate tensile modulus predictions. Our presented software incorporates sub-voxel fibre orientation distributions using ultra-low-resolution three-dimensional X-ray tomography data in a numerical model, providing an effective method for characterising these materials.
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| 2. |
- Auenhammer, Robert, 1991, et al.
(författare)
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X-ray scattering tensor tomography based finite element modelling of heterogeneous materials
- 2024
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Ingår i: npj Computational Materials. - 2057-3960. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Among micro-scale imaging technologies of materials, X-ray micro-computed tomography has evolved as most popular choice, even though it is restricted to limited field-of-views and long acquisition times. With recent progress in small-angle X-ray scattering these downsides of conventional absorption-based computed tomography have been overcome, allowing complete analysis of the micro-architecture for samples in the dimension of centimetres in a matter of minutes. These advances have been triggered through improved X-ray optical elements and acquisition methods. However, it has not yet been shown how to effectively transfer this small-angle X-ray scattering data into a numerical model capable of accurately predicting the actual material properties. Here, a method is presented to numerically predict mechanical properties of a carbon fibre-reinforced polymer based on imaging data with a voxel-size of 100 μm corresponding to approximately fifteen times the fibre diameter. This extremely low resolution requires a completely new way of constructing the material’s constitutive law based on the fibre orientation, the X-ray scattering anisotropy, and the X-ray scattering intensity. The proposed method combining the advances in X-ray imaging and the presented material model opens for an accurate tensile modulus prediction for volumes of interest between three to six orders of magnitude larger than those conventional carbon fibre orientation image-based models can cover.
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| 3. |
- Josefson, Lennart, 1954, et al.
(författare)
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LOAD CAPACITY OF SANDWICH PANEL WITH CORE FOAM EVALUATED BY 3-POINT BENDING TEST
- 2022
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Ingår i: Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE. ; 3
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Konferensbidrag (refereegranskat)abstract
- The classification society Bureau Veritas requires a structural assessment of composite materials structures to confirm the compliance with applicable rules, like 3-point bending tests. However, for sandwich panels with a low-density foam core, local phenomena like indentation and wrinkling may occur in the upper face sheet at the loading punch, thus the intended load capacity of the sandwich panel will not be reached. It is then proposed to perform complementary shear tests to capture the behaviour of the core of the sandwich panel. In the present paper, the load capacity in a 3-point bending test is simulated with emphasis on the influence of the constitutive modelling of the core foam, as calibrated against experimental results for shear tests. It is carried out as a benchmark exercise, with participation from three universities. The FE-simulations show that the shear test can be used to accurately model the load capacity of the core foam. However, for the 3-point bending test using specimen with a very high panel length/thickness ratio a large part of the load transfer is done in the upper face sheet with less involvement of shear in the core. Although core fracture is observed in the experiments, both the FE-simulated and experimentally found maximum load agree well with the load capacity as determined from analytical formula for local failure in the upper face sheet. The FE-simulated vertical displacement at maximum load differs though.
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| 4. |
- Oddy, Carolyn, 1994, et al.
(författare)
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A framework for macroscale modelling of inelastic deformations in 3D-woven composites
- 2021
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Ingår i: Mechanics of Materials. - : Elsevier BV. - 0167-6636 .- 1872-7743. ; 160
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Tidskriftsartikel (refereegranskat)abstract
- The use of 3D-woven composite materials has shown promising results. Along with weight-efficient stiffness and strength, they have demonstrated encouraging out of plane properties, damage tolerance and energy absorption capabilities. The widespread adoption of 3D-woven composites in industry however, requires the development of efficient computational models that can capture the material behaviour. The following work proposes a framework for modelling the mechanical response of 3D-woven composites on the macroscale. This flexible and thermodynamically consistent framework, decomposes the stress and strain tensors into two main parts motivated by the material architecture. The first is governed by the material behaviour along the reinforcement directions while the second is driven by shear behaviours. This division allows for the straightforward addition and modification of various inelastic phenomena observed in 3D-woven composites. In order to demonstrate the applicability of the framework, focus is given to predicting the material response of a 3D glass fibre reinforced epoxy composite. Prominent non-linearities are noted under shear loading and loading along the horizontal weft yarns. The behaviour under tensile loading along the weft yarns is captured using a Norton style viscoelasticity model. The non-linear shear response is introduced using a crystal plasticity inspired approach. Specifically, viscoelasticity is driven on localised slip planes defined by the material architecture. The viscous parameters are calibrated against experimental results and off axis tensile tests are used to validate the model.
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| 5. |
- Oddy, Carolyn, 1994, et al.
(författare)
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CALIBRATING MACROSCALE MODELS OF 3D-WOVEN COMPOSITES: COMPLEMENTING EXPERIMENTAL TESTING WITH HIGH FIDELITY MESOSCALE MODELS
- 2022
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Ingår i: ECCM 2022 - Proceedings of the 20th European Conference on Composite Materials: Composites Meet Sustainability. ; 4, s. 106-113
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Konferensbidrag (refereegranskat)abstract
- Composites with 3D-woven reinforcement could help fill a growing need for lightweight materials with improved material integrity and out-of-plane performance. Developing efficient computational tools to predict their behaviour, however, is key to facilitating their widespread adoption in various industrial applications. Macroscale models are one such tool. They consider an approach where the material model is homogeneous and anisotropic. While macroscale models are computationally efficient, they also require large scale, complex and time consuming experimental testing campaigns to characterise the material response. One promising avenue that is explored in this work, is the development of a characterisation test matrix, in which material data is acquired through a combination of experimental testing and simulation of a high fidelity mesoscale representative volume element. In this collaborative project, both experimental testing and mesoscale simulations are carried out in order to calibrate a macroscale model for 3D-woven composites. The results are validated against off-axis experimental tensile tests, as well as multiaxial load scenarios applied to the mesoscale representative volume element.
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| 6. |
- Oddy, Carolyn, 1994, et al.
(författare)
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Composite design for a foiling Optimist dinghy
- 2018
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Ingår i: Proceedings. - Basel Switzerland : MDPI. ; 2:6
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Konferensbidrag (refereegranskat)abstract
- In April 2017, a foiling Optimist dingy designed entirely by students, was successfully tested under standard sailing conditions in the waters outside Gothenburg. In order to achieve take of wind speeds as low as 6 m/s, a stiff and lightweight design of the dinghy and its foiling components was necessary. There have been few successful attempts to make an Optimist foil in a stable manner, as such there were no standards or recommendations available for the design. Therefore, a simulation driven structural design methodology for hydrofoils, centreboards, centreboard-to-hull connections, and necessary hull reinforcements using sandwich structures was adopted. The proposed design was then manufactured, allowing for a significantly stiffer hull and a 20% decrease in weight over a conventional Optimist. Excluding the rig and sail, the final weight came to 27 kg.
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| 7. |
- Oddy, Carolyn, 1994, et al.
(författare)
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Evaluation of damage initiation models for 3D-woven fibre composites
- 2019
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Ingår i: ECCM 2018 - 18th European Conference on Composite Materials. - : Applied Mechanics Laboratory.
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Konferensbidrag (refereegranskat)abstract
- Three dimensional (3D) fibre-reinforced composites have shown weight efficient strength and stiffness characteristics as well as promising energy absorption capabilities. In the considered class of 3D-reinforcement, vertical and horizontal weft yarns interlace warp yarns. The through-thickness reinforcements suppress delamination and allow for stable and progressive damage growth in a quasi-ductile manner. With the ultimate goal of developing a homogenised computational model to predict how the material will deform and eventually fail under loading, this work proposes candidates for failure initiation criteria. The criteria are evaluated numerically for tensile, compressive and shear tests. The extension of the LaRC05 stress based failure criteria to this class of 3D-woven composites is one possibility. This however, presents a number of challenges which are discussed. These challenges are related to the relative high stiffness in all directions, which produce excessively high shear components when projected onto potential off-axis failure planes. To circumvent these challenges, strain based criteria inspired by LaRC05 are formulated. Results show that strain based failure predictions for the simulated load cases are qualitatively more reasonable.
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| 8. |
- Oddy, Carolyn, 1994, et al.
(författare)
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Macroscale modelling of 3D-woven composites: Elasto-plasticity and progressive damage
- 2022
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683. ; 250
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing need across multiple industries for lightweight materials with improved material performance and reduced manufacturing costs. Composites with 3D-woven reinforcement could help fill this need. Their use however, requires the development of computationally efficient and industrially applicable material models to predict their non-linear behaviour. This work proposes a macroscale elasto-plasticity and damage model to capture the experimentally observed inelastic strains and stiffness reductions. The model is general, thermodynamically consistent and allows for various non-linear phenomena to be added and calibrated in a modular fashion depending on loading direction. Further it allows for a simplified parameter identification routine in which the damage and hardening laws are identified directly from experimental curves without the need for complex calibration routines. In order to demonstrate the applicability of the proposed macroscale model, focus is given to predicting the material response of a 3D glass fibre reinforced epoxy material system. The damage and hardening parameters are identified based on uniaxial tensile and in-plane shear experimental curves with unloading cycles. The model performance is validated against an off-axis tensile test with unloading cycles and shows good agreement to the experimental result.
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| 9. |
- Oddy, Carolyn, 1994
(författare)
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Macroscale Modelling of 3D-Woven Composites: Inelasticity, Progressive Damage and Final Failure
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Composites with 3D-woven reinforcement have been slowly making their way into different industrial applications. The interlacement of yarns, not only in-plane but also through-thickness, means that in many applications 3D-woven composites can outperform their laminated counterparts. In particular, this includes increased out-of-plane stiffness and strength, damage tolerance and specific energy absorption properties. The widespread adoption of 3D-woven composites in industry however, requires the development of accurate and efficient computational models that can capture the material behaviour. In terms of computational efficiency, the most promising choice is to treat the material as a homogeneous and anisotropic solid. This is referred to as a macroscale model. Developing a macroscale model, which can predict how 3D-woven composites deform and eventually fail, is the main focus of this work. Particular attention is given to predicting the relevant non-linear behaviours that lead to energy absorption. A framework for modelling the mechanical response of 3D-woven composites on the macroscale is presented. The proposed framework decomposes the stress and strain tensors into two main parts motivated by the material architecture. This allows for a convenient separation of the modelling of the shear behaviour from the modelling of the behaviour along each of the reinforcement directions. In particular, this division allows for a straightforward addition and modification of various non-linear phenomena observed in 3D-woven composites. As a next step, material modelling approaches are considered and added to the framework in order to capture these non-linear phenomena. This includes the use of a viscoelastic model as well as a combined elasto-plastic and continuum damage model to capture the development of permanent deformations and stiffness reduction mechanisms. Finally, an anisotropic phase-field model extension is developed in order to induce local softening and failure in a way which does not induce spurious mesh-dependencies in finite element analyses. The model predictions are compared to experimental tests and show good agreement. The aim has been to develop a model that allows the constitutive relations to be identified directly from uniaxial cyclic stress-strain tests without the need for complex calibration schemes. However, characterising the out-of-plane behaviour is not trivial. Therefore, the current work also explores the use of high-fidelity mesoscale models as an additional source of data for model calibration and validation.
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| 10. |
- Oddy, Carolyn, 1994
(författare)
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Modelling 3D-woven composites on the macroscale: Predicting damage initiation and inelastic phenomena
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Composites with 3D-woven reinforcement have been slowly making their way into different industries. The interlacement of yarns, not only in-plane but also through-thickness, means that in many applications 3D-woven composites can outperform their laminated counterparts. In particular, this includes increased out-of-plane stiffness and strength, damage tolerance and specific energy absorption capabilities. The widespread adoption of 3D-woven composites in industry however, requires the development of efficient computational models that can capture the material behaviour. The current work takes a few steps towards the long term goal of developing a phenomenologically based macroscale model to predict how 3D-woven composites deform and eventually fail under mechanical loading. Following a brief introduction to the research field, the feasibility of extending stress-based failure initiation criteria for unidirectional laminated composites, to 3D-woven composites is explored. In particular it is shown that the extension of the LaRC05 criteria presents a number of challenges and leads to inaccurate predictions. Instead strain-based failure criteria inspired by LaRC05 are proposed. They produce results that are qualitatively more reasonable when evaluated numerically for tensile, compressive and shear tests. As a next step, a thermodynamically consistent framework for modelling the mechanical response of 3D-woven composites on the macroscale is presented. The proposed framework decomposes the stress and strain tensors into two main parts motivated by the material architecture. This allows for the convenient separation of the modelling of the shear behaviour from the modelling of the behaviour along the reinforcement directions. In particular, this division allows for the straightforward addition and modification of various inelastic phenomena observed in 3D-woven composites. The framework is then used to simulate experimental results of a 3D glass fibre reinforced epoxy composite. A viscoelastic model is incorporated into the framework to capture non-linear behaviour associated with tensile loading along the horizontal weft reinforcement as well as non-linear shear behaviour. In detail, to capture the shear behaviour, a crystal plasticity inspired approach is considered. As such, it is assumed that inelastic strain strictly develops on localised slip planes oriented by the reinforcement architecture. The viscous parameters are calibrated against experimental results, and a preliminary validation of the model is performed for an off-axis tension test.
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