6,391 results for Conference item

  • A Fibre Compaction Model for Liquid Composite Moulding

    Kelly, Piaras (2007)

    Conference item
    The University of Auckland Library

    Liquid Composite Moulding (LCM) processes such as Resin Transfer Moulding (RTM) are widely-used to manufacture composite material components. The evaluation of resin fluid pressures and time to manufacture in these processes have been the study of many previous investigations. This study focuses on the forces which arise in LCM processes. A knowledge of these forces is of practical importance because they give the necessary tooling forces and also they help predict part thicknesses where force and thickness are coupled in complex processes such as Vacuum Assisted Resin Transfer moulding (VARTM). A phenomenological model is developed which predicts the forces required to compact certain fibrous materials in rigid moulds over a range of compaction velocities and volume fractions. Stress relaxation is accounted for. The model parameters can be obtained from a limited number of tests. The model is used to predict the stresses in dry and wet compacted fibrous materials, and the tooling forces in a complete LCM process. The model results agree well with experimental results.

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  • Simulation of the Complete Resin Infusion Process

    Govignon, Quentin; Bickerton, Simon; Kelly, Piaras (2008)

    Conference item
    The University of Auckland Library

    Resin Infusion (a.k.a. VARTM) is one of the Liquid Composite Moulding processes, for which liquid resin is drawn into dry fibre reinforcement. Resin Infusion is a closed mould process in which half of the mould is formed by a flexible vacuum bag. Significant cavity thickness changes occur during processing, due to the flexibility of the vacuum bag and the complex stress balance within the laminate. While the magnitude of thickness change is often small, the influence is significant on reinforcement fibre volume fraction. Dynamic changes in permeability during mould filling and post-filling have the potential to significantly affect the process. To simulate this behaviour, it is important to accurately model the compaction and relaxation of reinforcement in the dry and wet state. A series of tests have been completed to determine the compaction behaviour of an isotropic glass fibre mat. From these tests several non-linear elastic compaction models have been determined, and applied within a new Resin Infusion simulation. The process simulation, which addresses the pre-filling, filling and post-filling stages, is compared to an experiment employing a full field cavity thickness measurement apparatus, as well as measurement of resin pressure at three discrete points within the laminate.

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  • A Compaction Model for Liquid Composite Moulding Fibrous Materials

    Kelly, Piaras (2008)

    Conference item
    The University of Auckland Library

    Liquid Composite Moulding (LCM) processes are a family of advanced composite materials manufacturing processes, which includes the Resin Transfer Moulding (RTM), Injection/Compression Moulding (I/CM) and Vacuum Assisted Resin Infusion (VARI) processes. In an LCM process, many important manufacturing parameters depend on the stresses taken up by the fibrous material before, during and after the fluid-filling stage. For example, the tooling forces in an RTM process and the fill-time and part-thickness in a VARI process depend on this fibre stress. Fibrous materials respond to load in a complex manner, exhibiting viscoelastic effects and undergoing permanent deformation. A new framework for the mathematical modeling of these materials is proposed based on thermomechanical arguments. Physical phenomena of the microscale such as fibre bending, fibre-to-fibre friction and the concept of ???frozen energy??? are incorporated. The framework is demonstrated for the case of a fibrous material undergoing permanent deformations during a compaction/unloading cycle and the results are compared with experiment.

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  • Simulation and Verification of Local and Global Forces Exerted on Rigid LCM Tools

    Walbran, William; Bickerton, Simon; Kelly, Piaras (2008)

    Conference item
    The University of Auckland Library

    The SimLCM code is being developed at the University of Auckland as a generic Liquid Composite Moulding (LCM) simulation. A comprehensive tooling force analysis has been implemented, providing local and global predictions. Complex geometries require the consideration of both the normal and tangential stress components acting on mould surfaces, due to the compaction of fibre reinforcement and internally generated resin pressures. This approach is required as SimLCM will be extended from the rigid tool (i.e. RTM, I/CM) to flexible (i.e. Resin Infusion, VARTM) and semi-rigid tool (i.e. RTMLight) LCM techniques. Several elastic and viscoelastic reinforcement compaction models have been developed to address both dry and wet response, and are implemented within SimLCM. A simple friction based model is included to model the tangential stress component, allowing consideration of complex non-planar part geometries. This paper will demonstrate current capability of the package, and present experimental verification studies.

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  • Predicting Stress Distribution Exerted on LCM Tools during Filling Phases

    Walbran, William; Bickerton, Simon; Kelly, Piaras (2008)

    Conference item
    The University of Auckland Library

    Mould tools used for LCM processes such as Resin Transfer Moulding (RTM) and Injection/Compression Moulding (I/CM) must withstand local forces due to resin pressure and compaction of the fibre reinforcement. Prediction of these tooling forces will allow cost effective mould design and process selection. A series of RTM and I/CM experiments have been undertaken, monitoring total clamping force and normal stress distribution acting on mould surfaces. A mixed elastic and a visco-elastic reinforcement compaction model have been used to model these processes, both being compared to experimental data. Both models show good agreement to experiment during compaction phases, however the visco-elastic model matches the experimental data significantly better during periods influenced by stress relaxation. Circumferentially averaged stress distributions are also compared at key points in the process, both models showing good qualitative agreement to experiment, and the RTM cases also matching well quantitatively. Overall, the RTM process has been modeled accurately, while some discrepancy exists for I/CM during secondary compaction, when fluid is compressed along with reinforcement.

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  • Global Optimization of Mould Filling Parameters during the Constant Speed Injection Compression Moulding Process

    Na, Sam; Kelly, Piaras; Bickerton, Simon (2008)

    Conference item
    The University of Auckland Library

    Injection Compression Moulding (I/CM) is one of the many Liquid Composite Moulding (LCM) manufacturing processes for composite materials. In this study, process objective functions are defined and minimized using a global optimization technique which has been developed for this study. Different weighting values are assigned in the objective function to characterise the importance of process cycle time or clamping force requirements. The University of Auckland mould filling simulation software SimLCM has been used to simulate the I/CM process. Two different geometries are used for the optimization study, one planar and one non-planar, to demonstrate and verify the performance of the optimization algorithm. It is proven that the problem is non-convex indicating the existence of multiple local minima. The problem has been broken down into three sub-problems to locate the global minimum. Methods are presented which can be utilized by the manufacturer to decide upon the best combination of process parameters to suit specific desired outcomes.

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  • A Thermomechanical Constitutive Model for Fibrous Reinforcements

    Cheng, Jonathan; Kelly, Piaras; Bickerton, Simon (2009)

    Conference item
    The University of Auckland Library

    In Liquid Composite Moulding processes, many important manufacturing parameters and final properties of the part are influenced by the constitutive behaviour of fibrous reinforcements. A thermomechanical model for the response of fibrous materials to compaction is presented. Rate-dependent and rate-independent features observed in experimental data are reproduced by the model.

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  • Reducing setup costs: Tooling force prediction in resin transfer moulding (RTM) and compression RTM

    Walbran, WA; Verleye, B; Bickerton, Simon; Kelly, Piaras (2009)

    Conference item
    The University of Auckland Library

    Mould tools used for Liquid Composite Moulding (LCM) processes such as Resin Transfer Moulding (RTM) and Compression RTM (CRTM) must withstand significant forces generated by the fluid and the fibrous reinforcement. Prediction of these forces will allow for optimizations in setup costs and time, and maximize the usage of the capabilities of peripheral equipment (such as presses). SimLCM is being developed at the University of Auckland as a generic LCM simulation packaged. It has the capability to predict clamping forces and stress distributions acting on mould tools during complete moulding cycles. Both mixed-elastic and viscoelastic reinforcement compaction models are implemented within the package. A series of experiments, both planar (circular flat plate) and non-planar (truncated pyramid), have been undertaken to validate predictions made using SimLCM. Consideration of both the normal and shear components of the fibre preform compaction stress and the internally generated fluid pressure is required for non-planar geometries. This is especially important to extend the capabilities of SimLCM from rigid tool processes (such as RTM and CRTM) to include flexible tool processes such as RTM Light and Vacuum Assisted RTM (VARTM). A friction-based model is used to account for the shear component of compaction stress. In general, predictions for the planar cases are very good, with the viscoelastic model providing significant improvement over the mixed-elastic model during stress relaxation phases. However, for the non-planar cases presented, the peak force is under predicted during preform compaction, and over predicted during the fluid compression phase of CRTM. The under prediction is potentially due to irregularities with the preforms for the non-planar geometry, and is the subject of ongoing research. The over prediction of the force during the fluid compression phase of CRTM is primarily due to internally generated fluid pressure during fluid compression as a result of significant race tracking during the fluid filling phase This is not well-modeled currently by SimLCM and is the subject of ongoing work.

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  • Optimisation of mould filling parameters of the compression resin transfer moulding process

    Hsu, S; Ehrgott, Matthias; Kelly, Piaras (2010)

    Conference item
    The University of Auckland Library

    The Compression Resin Transfer Moulding Process (CRTM) is a popular type of Liquid Composite Moulding Process (LCM) commonly used for manufacturing composite materials. In this paper we consider the optimisation of the manufacturing processing time and the machine tooling force for the CRTM process. Since this process requires large forces during compression, force evaluation and prediction provides great advantages for the industry as it enables structural analysis of the moulds. Not only it does lead to cost effective tooling design, it also allows for proper selection of cost effective moulds and supporting equipment. The tooling force, moreover, is in conflict with manufacturing time, which is another objective of particular interest in the industry. In recent years, the advancement of CRTM simulation software allows accurate prediction of the processing objectives thus making it unnecessary to run through the expensive experiments physically. In this process, we use such a simulation software called SimLCM and combine it with a popular NSGA-II evolutionary multi-objective optimisation (EMO) algorithm to optimise maximum tooling force and processing time with respect to three manufacturing parameters. The EMO algorithm uses SimLCM as a black box to evaluate the objective function values for a population of solutions. We report results on a simple rectangular plate model (for calibration) and an industrial example.

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  • Simulation and experimental validation of force controlled compression resin transfer moulding

    Verleye, B; Walbran, William; Bickerton, Simon; Kelly, Piaras (2010)

    Conference item
    The University of Auckland Library

    The simulation of composite manufacturing processes is a great aid to obtaining efficient production and high quality parts. The mould and process design must allow for fast filling times as well as dry???spot free parts. Besides an accurate simulation of the resin flow through the reinforcement, the compaction response of the preform is also needed. The stress response of the textile to compaction has an influence on the local and global forces exerted on tooling. The numerical prediction of the clamping force helps to trade off fast production times against affordable machinery. This article describes the accurate simulation of force controlled Resin Transfer Moulding RTM and Compression RTM, and compares results of simulations with experimental data. A parametric study is performed in order to minimise the simulation time without compromising the accuracy of the results. The controlled force algorithms have been implemented within SimLCM, a code under development at the University of Auckland to address the liquid composite moulding LCM family of manufacturing processes. With these new tools the trade???off between production process time and equipment cost can be considered, and optimal process design solutions found.

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  • Effects of Polymer-Modified Binder on Deformation and Cracking Performance of Recycled Asphalt Paving Mixes

    Kodippily, Sachi; Holleran, G; Wilson, Douglas; Henning, Theunis (2015)

    Conference item
    The University of Auckland Library

    Developing technologies that provide sustainable solutions for future pavement construction is vital given the ever-increasing demand on the supply of bitumen and good-quality pavement construction materials. Recycled Asphalt Pavements (RAP) is a technology that presents many benefits in terms of both cost and environmental savings. The presented study investigated the effect of polymers on the deformation (rutting) resistance and cracking resistance of RAP mixes. In this study, laboratory testing was conducted on six paving mixes manufactured using various proportions of RAP and polymers. The mixes contained 15%RAP, 30%RAP, a control mix, 15%RAP+polymer, 30%RAP+polymer and polymer only mix. Samples were subjected to dynamic modulus testing, flow number testing and overlay testing using an Asphalt Mixture Performance Testing machine. The inclusion of RAP resulted in notable increases in the stiffness of the mixes, particularly with a 30% RAP proportion. The addition of polymers reduced the stiffness of the mixes, most notably in the 30% RAP mix while no change in stiffness was observed for the 15% RAP mix. The presence of polymers improved the rutting resistance of all the mixes, although the presence of polymers in conjunction with RAP decreased the reflective cracking resistance of the mixes, where when the RAP content was high, the negative effects of polymers on the cracking performance of the mixes were more significant. The research results provided a valuable understanding of the behaviour of RAP mixes, and in particular, this study provided valuable performance specifications for RAP mixes for the pavement construction industry in New Zealand.

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  • Optimisation of mould filling parameters during the compression resin transfer moulding process

    Kam, W; Kelly, Piaras; Ehrgott, Matthias; Verleye, B; Bickerton, Simon (2010)

    Conference item
    The University of Auckland Library

    manufacture of composite materials. In this process, a fibrous preform is first placed in a mould and then the mould is partially closed. The resin is then injected, before the mould is finally closed fully, driving the fluid through any remaining dry regions in the fabric. Finally, the resin is allowed to cure and the part is de-moulded. A number of manufacturing parameters affect the efficiency and cost of the CRTM process. Principal amongst these are the fluid injection pressure, the velocity at which the mould is closed and the thickness of the preform at which the resin is first injected. The goal of this study was to optimise the choice of the manufacturing parameters, such that the process time was kept short and the maximum force necessary to close the mould was kept low. This non-linear non-convex multi-objective optimisation problem was solved using a genetic algorithmic approach, with the algorithm interacting with SimLCM, a composites manufacturing process simulation software developed at the University of Auckland. Full-scale analyses were carried out, providing valuable information, regarding process parameters to use, for manufacturers.

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  • Simulation of force and velocity controlled compression RTM

    Verleye, B; Walbran, William; Bickerton, Simon; Kelly, PA (2010)

    Conference item
    The University of Auckland Library

    The simulation of composite manufacturing processes is a great aid to obtaining efficient production and high quality parts. The mould and process design must allow for fast filling times as well as dry-spot free parts. Besides an accurate simulation of the resin flow through the reinforcement, the compaction response of the preform is also needed. The stress response of the textile to compaction has an influence on the local and global forces exerted on tooling. The numerical prediction of the clamping force helps to trade off fast production times against affordable machinery. This article describes the accurate simulation of force controlled Resin Transfer Moulding (RTM) and Compression RTM, and compares results of simulations with experimental data. A parametric study is performed in order to minimise the simulation time without compromising the accuracy of the results. The controlled force algorithms have been implemented within SimLCM, a code under development at the University of Auckland to address the liquid composite moulding (LCM) family of manufacturing processes. With these new tools the tradeoff between production process time and equipment cost can be considered, and optimal process design solutions found.

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  • Numerical Simulation and Aeroacoustic Noise Modelling of the CART-2 Wind Turbine

    Wasala, Sahan; Norris, Stuart; Cater, John (2014-11-25)

    Conference item
    The University of Auckland Library

    Acoustic noise disturbance is one of the major factors which slows wind farm development near urban areas. This emphasises the importance of accurate estimation of the noise levels before the production and installation of wind turbines. In the present work, a Large Eddy Simulation (LES) of the region of the blade with the strongest acoustic sources, based on Oerlemans' acoustic camera measurements, is carried using a computational domain of an annulus section, which leads to a significant reduction of computational expense. The Ffowcs-Williams and Hawkings (FWH) acoustic analogy is used to predict the far field sound. The numerical results for the CART-2 wind turbine blade show good agreement with the available experimental data.

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  • Transverse compression properties of textile materials, International conference on textile engineering and materials

    Kelly, Piaras; Bickerton, Simon; Cheng, Jonathan (2011)

    Conference item
    The University of Auckland Library

    The response of textile materials to transverse compression is of great importance in many applications. In this paper is discussed the mechanical properties of textile materials when subjected to transverse compression. The response of a textile to load is very non-linear and inelastic. The response is viscoelastic (there are rate effects) and plastic (there are permanent deformations). It is shown that energy is stored in a textile when it is loaded, and that some of this energy is not released when the material is unloaded, but instead is locked into its structure. This locked energy cannot be released unless the structure is placed in tension. A thermomechanical framework is introduced which incorporates the textile locked energy. Models are developed which predict well the response of textiles to load.

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  • Simulation and tooling forces exerted on rigid non-planar LCM tools

    Walbran, W; Verleye, B; Bickerton, Simon; Kelly, Piaras (2010)

    Conference item
    The University of Auckland Library

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  • Performance of recycled asphalt pavement mixes: comparing New Zealand experience with American experience

    Kodippily, Sachi; Holleran, G; Holleran, Irina; Henning, Theunis; Wilson, Douglas (2014)

    Conference item
    The University of Auckland Library

    Developing technologies that provide sustainable solutions for future pavement construction is vital given the ever-increasing demand on the supply of bitumen and good-quality pavement construction materials. Recycled Asphalt Pavements (RAP) is a technology that presents many benefits in terms of both cost and environmental savings. The presented paper investigated the use of RAP in New Zealand with the aim of establishing RAP as a standard pavement construction technology. The study findings were used to establish performance standards for RAP mixes in New Zealand.

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  • A 2.5 Simulation of the Resin Infusion Process addressing complex reinforcement compaction response

    Verleye, B; Kelly, Piaras; Bickerton, Simon (2010)

    Conference item
    The University of Auckland Library

    The simulation of composite manufacturing processes is a great aid to obtaining efficient production and high quality parts. The mould and process design must allow for fast filling times as well as dry-spot free parts. In previous work we presented our software SimLCM for the simulation of force and velocity controlled Resin Transfer Moulding (RTM) and Compression RTM. These are two examples of the general Liquid Composite Moulding (LCM) group of processes. Another recently popular subclass is Resin Infusion (RI), also know as Vacuum Assisted RTM. The simulation of RI adds an extra difficulty to the simulation process, as the height of the preform will change locally because of the filling. In contrast to CRTM, this change of height is not imposed, and thus not known beforehand. This paper describes the extension of SimLCM to the simulation of RI processes. The results of the simulations are compared with results from other programs that use different techniques, and also with experimentally obtained data found in literature. The comparison between simulation and experiment is found to be excellent.

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  • A Rate-independent thermomechanical Constitutive Model for Fibrous Reinforcements

    Cheng, Jonathan; Kelly, Piaras; Bickerton, Simon (2010)

    Conference item
    The University of Auckland Library

    In Liquid Composite Moulding (LCM) processes, the constitutive behaviour of fibrous reinforcements has a strong bearing on the choice of manufacturing parameters and final part properties. In many LCM processes, the fibrous preform is subjected to loading and unloading, the latter also occurring during filling and post-filling phases of the manufacturing process. Fibrous materials display inelastic behaviour with rate-dependent and rate-independent components and this must be modelled accurately over several load-unload cycles in order to accurately simulate such processes. An important feature of the material behaviour is its unchanging response to successive load cycles once a large number of load cycles have been applied. Inelastic effects such as fibre-fibre frictional sliding occur during loading as well as unloading and the inelastic deformation remaining after successive cycles appears unchanged. The model presented is developed within a thermomechanical framework and reproduces such behaviour using a single internal variable to account for inelasticity. It is compared to cyclic loading experiments and serves as a starting point for the incorporation of effects such as cyclic softening and rate-effects through additional internal variables.

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  • Observations from the filling and post-filling stages of axisymmetric liquid composite moulding with flexible tooling

    Timms, J; Govignon, Quentin; Bickerton, Simon; Kelly, Piaras (2010)

    Conference item
    The University of Auckland Library

    This paper presents experimental observations from the filling and postfilling stages of 1D axisymmetric Resin Infusion (VARTM) and RTM Light. A series of experiments have been performed to investigate the influence of mould flexural stiffness and fill mode on fluid pressure, cavity thickness, filling stage time, and postfilling stage time. Observations are also made on the effect of those parameters on the repeatability of nominally identical experiments.

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