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  • 1.
    Lundström, Staffan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nordlund, Markus
    Investigation of transient flow behaviour in dual-scale porous media with micro particle image velocimetry2006In: Proceedings, 4th International Scientific Colloquium Modelling for Material Processing, 2006, p. 117-122Conference paper (Refereed)
    Abstract [en]

    Injection processing of composite materials most often includes infiltration of a thermoset resin into a multi-scale porous fabric. Controlling the fluid flow within the multiscale fabric is essential for the quality of the final composite material, since the transport of fluid between regions with different scales plays an important role in phenomena such as void formation and filtration of particle doped resins. In this work, the transient flow behaviour in dual scale porous media is investigated with Micro Particle Image Velocimetry in order to enhance the knowledge and control of the processing of multi-scale composites so that their quality can be improved. Experiments show that the fluid transport between the two scales can be controlled by the injection velocity. Validation of the measured velocity fields furthermore shows excellent agreement with theory.

  • 2.
    Lundström, Staffan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Nordlund, Markus
    Numerical calculations of the permeability of non-crimp fabrics2003In: ICCM-14: 14th International Conference on Composite Materials : July 14-18, 2003, San Diego, California, USA, Dearborn, Mich: Arctic Monitoring and Assessment Programme, 2003Conference paper (Refereed)
  • 3. Michaud, V.
    et al.
    Nordlund, Markus
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Månsson, J-E
    Capillary phenomena in liquid composite moulding2007In: 1CD-ROM proceedings of the Sixtennth International Conference on Composite Materials, July 8 - 13, 2007, Kyoto, Japan: A giant step towards environmental awareness: from green composites to aerospace / [ed] Kazuro Kageyama, Kyōto, 2007Conference paper (Refereed)
    Abstract [en]

    In liquid composite moulding, capillary phenomena take place as the fibre/air interface is progressively replaced by the fibre/resin interface. These effects are often neglected when computing the flow front progression into the fibre preform, because the surface tension of the resins is low. However, these are recognized to exert an influence on the final void content of the part. In this article, we present experimental results from unidirectional infiltration of an epoxy resin under constant flow rate into non-crimp fabrics. The inlet pressure rise is shown to deviate from linearity, indicating a progressive saturation. A multiphase flow approach is proposed to model infiltration, assuming saturation curves and relative permeability dependence on saturation based on soil science literature. Numerical results using a FEM code show trends that are in good qualitative agreement with experimental results. The interest and validity of this approach is then discussed.

  • 4.
    Nordlund, Markus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Permeability modelling and particle deposition mechanisms related to advanced composites manufacturing2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Advanced composite materials reinforced by Non-Crimp Fabrics (NCFs) are becoming increasingly popular for high performance, light weight, complex structures, due to their high mechanical properties and relatively cheap production costs. These materials, not only improve the structural properties, but also induce great possibilities for reduced fuel consumptions for aircrafts and automotives, due to their high strength to weight ratio. In recent years, even more advanced composite materials have been developed, in order to meet the increasing demands of optimized composite structures from the manufacturers. These materials can have functional properties such as thermal resistance, electromagnetic shielding, conductivity, sensor or self healing properties integrated into the material through functional filler-particles, which are pre-mixed into the resin before being injected into the preform. In order to use these kind of materials in high-end applications, they need to be of highest possible quality, meaning few defects and homogeneous distribution of the functionality and often also produced at the lowest possible cost. An extensive control of the manufacturing is therefore required, since defects and inhomogeneous particle distributions are usually initiated there. During the impregnation stage, resin flows at low Reynolds number through a porous medium in the form of a fibre reinforcement. In order to control the filling process, the permeability of the reinforcement need to be determined accurately. Initially, the local permeability distribution of biaxial NCFs is investigated. Three types of unit cells are identified, where each one represents a specific geometrical feature originating from the stitching process. The local permeabilities of these unit cells are computed for various dimensions by combining Computational Fluid Dynamics and Darcy’s law, in order to scrutinize the importance of the different features and fabric dimensions on the local permeability. It is, for example, shown in this study, that the widths and heights of the interbundle channels in NCFs and the fibres crossing them between adjacent stitches, have the greatest influence on the local permeability, while the stitching thread itself and the shape of the fibre bundles affect it less. In order to improve the speed of the local permeability computations, without reducing the accuracy, a model as simple as possible is sought after. An investigation of whether or not the fibre bundles need to be included into the permeability model is therefore performed. Modelling the fibre bundles of NCFs is proved to be irrelevant for the local permeability for high fibre volume fractions inside the fibre bundles, fb, while the fibre bundles is shown to be important for low fb:s. A new model, including the effect from the fibre bundles without modelling them directly, is developed for low fb:s, in order to facilitate faster, but still accurate permeability computations on models with reduced fluid domains for the entire span of fb:s. Knowing the influence from the geometry on the local permeability, a global permeability model is developed for biaxial NCFs. Unlike most other developed permeability models for NCFs, this model comprises the complex geometrical features originating from the stitching process as well as the spatial variations of the fabric dimensions. The model is based on a network of interconnecting unit cells, with local permeability values calculated numerically. Validation of the global permeability model shows that inclusion of the features from the stitching process into the permeability model, together with an accurate determination of the average dimensions of the interbundle channels, are fundamental, in order to predict the global permeability of NCFs. The second topic considered in the present thesis is related to the inhomogeneous particle distribution, resulting in poor mechanical and functional properties of liquid composite moulded functional composites. To be able to control the distribution of filler-particles in the composites, knowledge and control about the particle deposition mechanisms occurring during the filling process are mandatory. The mechanisms and their resulting particle depositions are examined by microscopic imaging and from velocity fields measured by Micro Particle Image Velocimetry, on the flow in simplified miniscule geometries. In particular, two main mechanisms are studied, being filtration during fibre bundle impregnation and filtration induced by stationary flow through fibre bundles. These mechanisms, not only result in particle depositions, but also in particle-free regions, which are also observed in the analysis of a macroscopic vacuum infused, real biaxial NCF. Several suggestions of adjustments of the process and material parameters, such as the injection flow rate, fabric architecture and orientation, are furthermore outlined, with the aim of reducing these depositions.

  • 5. Nordlund, Markus
    Permeability of non-crimp fabrics: a computational fluid dynamics approach2004Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the present market for manufacturing of high performance structural parts for various applications such as aerospace, transportation, infrastructure, marine, sports and recreation, low weight, high performance composites are preferable. Non-Crimp Fabrics (NCFs) are often used for such applications due to its high mechanical properties and often cost effective production. NCFs usually consist of layers of straight fibre bundles oriented in different directions stitched together. Apart from the fibre structure of the fabric, the properties of the formed composite material are dependent on the resin matrix, which bonds the fibres within the fibre bundles as well as between the fibre bundles together. Hence, in order to maintain the high physical properties of NCFs after the composite has been formed, control of the manufacturing is vital in order to minimize defects in the resulting material. An understanding of the manufacturing also contributes to more effective productions and prediction models are therefore highly desirable. One important stage is the impregnation of the fibres by the liquid resin. In order to control the filling of resin through the fabric, the permeability of the fabric must be known. The permeability is directly dependent of the geometry of the detailed fabric and will therefore generally vary within a fabric due to local geometry variations. The permeability can be determined either by experiments or by mathematical models describing the fabric geometry. Experimental work is often very time-consuming and the prediction models that are often used to predict the permeability are relations originating from granular porous media or with homogenous fibre arrangements. In order to predict the permeability more accurately the complex geometry of the NCF, that is its three dimensional nature as well as the effects from the stitching process, has to be taken into account as well as perturbations of the fabric geometry. In the present work Computational Fluid Dynamics (CFD) is used to solve the flow field through the complex geometries. The thesis consists of three papers. In the first paper (Paper A) the permeability of two unit cells of a biaxial NCF are studied. A profound study of the numerical accuracy is carried out of the CFD simulations together with verification by analytical expressions. The results are furthermore validated to previously produced experimental data. The verification showed good agreement with the analytical expressions whereas the calculated permeability showed a large over-prediction of the permeability compared to the experimental data. The presence of a thread proved to have influence on the unit cell permeability. In the second paper (Paper B) the local permeability of a fabric was studied by CFD simulations of unit cells in order to determine how local geometrical features and variations affect the local permeability within a fabric. It was shown that the width and height of the inter-bundle channels have great influence on the permeability as well as the presence of thread and fibres crossing the inter-bundle channels between stitches. The results indicate that there is a significant distribution of the local permeability within a fabric due to the stitching process and its geometrical perturbations. In the third paper (Paper C) the local permeability distribution, due to the effects from the stitching process and geometry perturbations, in the fabric was included in a statistically based network model for the global permeability of the NCF. The results from the network model, including the thread, fibre crossings, perturbations of the inter-bundle channel dimensions, showed that the fibre crossings, which result from the stitching process, have high influence on the global permeability as well as the mean value of the inter-bundle channel width. The result is validated against experimental permeability data and shows good agreement when the fibre crossings are included in the model.

  • 6. Nordlund, Markus
    et al.
    Fernberg, S.P.
    SICOMP AB, Swedish Institute of Composites.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Particle deposition mechanisms during processing of advanced composite materials2007In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 38, no 10, p. 2182-2193Article in journal (Refereed)
    Abstract [en]

    Liquid composite moulding of advanced composite materials often comprises infiltration of a particle-filled resin into a multi-scale porous fabric. These injections/infusions are subject to severe particle depositions inside the reinforcement, leading to undesired inhomogeneous mechanical and functional properties. Hence, the mechanisms for particle depositions are investigated by detailed meso-scale experiments, analysed by microscopic imaging and micro-particle image velocimetry, and macroscopic infusions of a biaxial non-crimp fabric. It is shown that two main particle deposition mechanisms are filtration during fibre bundle impregnation and filtration induced by stationary flow through fibre bundles. It is also clarified where in the reinforcement the particles will deposit. Finally, a number of suggestions on how to process advanced composite materials with a more homogeneous particle distribution are launched.

  • 7. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    An investigation of particle deposition mechanisms during impregnation of dual-scale fabrics with micro particle image velocimetry2010In: Polymer Composites, ISSN 0272-8397, E-ISSN 1548-0569, Vol. 31, no 7, p. 1232-1240Article in journal (Refereed)
    Abstract [en]

    Injection moulding processing of composite materials most often includes infiltration of a thermoset resin into a multi-scale porous fabric. Controlling the fluid flow within the multi-scale fabric is essential for the quality of the final composite material, since the transport of fluid between regions with different scales is of importance for phenomena such as void formation and filtration of particle doped resins. Hence, the transient flow behaviour in dual scale porous media is investigated in detail with Micro Particle Image Velocimetry. These experiments show that the fluid transport between the two scales can be controlled by the injection velocity. Validation of the measured velocity fields furthermore shows excellent agreement with theory and that transport between the two scales can be substantial at the flow front but negligible up-stream it. POLYM. COMPOS

  • 8. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effect of geometrical features of non-crimp fabrics on the permeability2004In: From nano-scale interactions to engineering structures: ECCM 11, 11th European Conference on Composite Materials ; May 31 - June 3, 2004, Rhodes, Greece / [ed] Costas Galiotis, Rhodos, 2004Conference paper (Refereed)
  • 9. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Effect of multi-scale porosity in local permeability modelling of non-crimp fabrics2008In: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 73, no 1, p. 109-124Article in journal (Refereed)
    Abstract [en]

    The influence of multi-scale porosity of fibre reinforcements on local permeability is investigated, in order to determine the possibility of simplifying permeability models for more efficient permeability calculations. Unit cell models of a biaxial Non-Crimp Fabric are developed and used to investigate, whether or not the porous bundles can be excluded, when modelling the local permeability. Numerical accuracy of calculations is controlled to guarantee the quality of the results and the conclusions drawn from them. It is found that fibre bundles with high fibre density can be excluded from permeability models, while bundles with low fibre volume fractions need to be included. A new method to model the local permeability of multi-scale reinforcements is developed and verified for low fibre density in the bundles. In this method, the effects of the flow inside the fibre bundles are included through modifications of the boundary conditions of a single-scale model representing the interbundle regions. The local permeability of multi-scale reinforcements can, therefore, be calculated by models with simplified fluid domains for all fibre bundle porosities, instead of being calculated by models consisting of the entire multi-scale geometry.

  • 10. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Experimental study of particle filtration in dual-scale porous media2006In: 2nd International Symposium Nanostructured and Functional Polymer-based Materials and Composites, Lyon, May 29 - 31,2006, Impact press, 2006Conference paper (Refereed)
  • 11. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Numerical study of the local permeability of noncrimp fabrics2005In: Journal of composite materials, ISSN 0021-9983, E-ISSN 1530-793X, Vol. 39, no 10, p. 929-947Article in journal (Refereed)
    Abstract [en]

    Noncrimp stitched fabrics (NCFs) are often used as reinforcing materials in high-performance composite materials. Prediction models of the processing stage of the manufacturing are highly desirable in order to enhance the control of the process and enable the production of materials with higher quality. In NCFs, layers of parallel fiber bundles consisting of a large number of fibers are stitched together with other layers to form a network of interbundle channels in different directions. In earlier works, numerical simulations on unit cells had been performed in order to predict the global permeability of NCFs. It was shown that features like the thread influence the local permeability of the unit cells and therefore, the local permeability distribution of a fabric also. Furthermore, this influences the global permeability of the entire fabric. In the present paper, different geometrical features are therefore studied in order to investigate their influence on the local permeability within an NCF. The stitching process in addition to the interbundle channels, gives rise to two geometrical features, the thread which penetrates the channels and the crossing of fibers between two neighboring fiber bundles. The influences of these two features on the local permeability are studied together with variations of other geometrical parameters of the fabric. Computational Fluid Dynamics are used for the flow simulations in order to calculate the local permeability for the different unit cells. To ensure quality and trust, the numerical accuracy of the simulations is also studied. This work proves that the thread and the crossings, as well as the variations of the width and the height of the interbundle channels, have great influence on the local permeability. Prediction models therefore, have to take these features as well as geometry distortions, which influence the local permeability distribution, into account in order to make accurate predictions of the global permeability of a fabric.

  • 12. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Permeability network model of non-crimp fabrics2005In: Fifteenth international conference on composite materials (ICCM-15): extended abstracts : 27 June - 1 July 2005, Durban, South Africa / [ed] Viktor E. Verijenko, Durban: Centre for Composite and Smart Materials and Structures, University of KwaZulu-Natal , 2005Conference paper (Refereed)
  • 13. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Jakovics, A.
    University of Latvia.
    Permeability network model for non-crimp fabrics2006In: Composites. Part A, Applied science and manufacturing, ISSN 1359-835X, E-ISSN 1878-5840, Vol. 37, no 6, p. 826-835Article in journal (Refereed)
    Abstract [en]

    In this work a global permeability model is developed and applied to a biaxial Non-crimp stitched fabric (NCF). This model focuses on a detailed meso-scale description of the fabric geometry, which takes into account the local permeability distribution in a fabric due to perturbations of the geometry as well as the geometrical features which arise from the stitching process. It is shown in this work that these features significantly affects the global permeability. The influence of the amount and type of perturbation of a fabric is also studied in this work. It is shown that perturbation of the fabric geometry affect the global permeability but not as much as the stitching process. The model developed is finally validated with experimental permeability data and it is suggested how to use the model for an arbitrary lay-up.

  • 14. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Frishfelds, Vilnis
    Jakovics, Andris
    Application of permeability network model to non-crimp fabrics2004In: The XIII International Conference on Mechanics of Composite Materials, 2004Conference paper (Refereed)
  • 15. Nordlund, Markus
    et al.
    Lundström, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Fluid and Experimental Mechanics.
    Michaud, V.
    Månson, J-A
    Wetting dynamics of nano-charged resins in multi-scale porosity2005In: Proceedings of the International Conference on Science and Technology of Composite Materials: COMAT 2005, 2005Conference paper (Refereed)
1 - 15 of 15
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