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Abstract
The wind turbine blade is a key component of wind turbine generator system, and helps capture wind energy effectively. The way of RTM resin transfer molding is generally used at home and abroad for blade manufacturing process. In order to ensure the quality of product, computer simulation analysis and experimental verification should be conducted before producing. Moldflow was used to simulate the process of wind turbine blade RTM. Based on that, variation diagrams about filling time, temperature, buckling deformation, pressure and so on are obtained. The results of analysis and comparison of with and without cooling, as well as optimize the defects existed indicate that cavitations concentrate in roots and edge of the blade, gas exhaust mold easily, there is no need to open up air vent additional; In filling stage, mold clamping force gradually increase slowly, in packing stage, mold clamping force sharply increase to reach peak, the mold clamping force disappears after packing; filling time with cooling process is longer than that without cooling process. It provides an important reference for wind turbine blade design and manufacture.
... En 2013, Li et al. [12] realizaron la simulación del proceso RTM en la fabricación de una pala de turbina eólica mediante el software Moldflow. Se desarrollaron varias simulaciones, entre ellas: tiempo de llenado, temperatura, deformación por pandeo, evolución de la presión, entre otros, comparando procesos con y sin refrigeración. ...
To provide an alternative for manufacturing auto parts using composite materials, the Vacuum Assisted Resin Transfer Molding (VARTM) process was utilized to prototype the bumper for the Chevrolet Aveo vehicle. This technique emerges as an alternative for composite material manufacturing, allowing for rapid and high-quality production of advanced composites. In this study, a hybrid composite material reinforced with fiberglass, cabuya fiber, IN2 epoxy resin, an infusion mesh, peel ply, and a vacuum bag was employed. To optimize the VARTM process in bumper prototyping, several simulations of resin flow were conducted with different locations of resin injection and vacuum entry points. Autodesk Moldflow Insight software facilitated the modification and addition of resin injection points to observe the flow evolution, thus determining the filling time for each proposed design. Six different designs were applied for the bumper mold filling. The proposed linear flow design reduced the total filling time of the bumper mold by 81.56% compared to the other five designs analyzed. The result of the numerical simulation was validated through the experimental process, where a high degree of concordance in the mold filling time was achieved between both methods.
RTM (Resin Transfer Moulding) is a closed mould process in which matrix resin is injected into a mould filled with a fibre preform. There are many RTM process parameters influencing the quality of the final product. The objective of this work was to study resin injection pressure. For this purpose, an amine curing epoxy resin was injected, using a small laboratory size RTM machine, into a flat mould filled with woven carbon fibre layers. Five different resin injection pressure levels; 1, 2, 3, 4, and 5 atm (101, 203, 304, 405, and 506 kPa) were used to produce composite sample plates. Specimens for mechanical testing and microscopic examination were extracted from various parts of the plates.
Generally, it was observed that an injection pressure level of 2 atm (203 kPa) resulted in the best mechanical performance in the specimens, mainly due to better fibre impregnation by the uniform resin flow, minimising void formation. Increasing the resin injection pressure level above 2 atm (203 kPa) resulted in differences between “macroflow” (around fibre bundles) and “microflow” (through the fibres) leading to non-uniform resin flow and void formation, hence a reduction in the mechanical properties.
The effects of hot runner system on injection moulding process and properties of injected part have been investigated from various aspects in comparison with conventional runner system. A two-cavity mould which can be used for both of the runner systems was designed and produced so as to conduct all experiments on the same mould, and to compare the results precisely. In the experiments, acrylonitrile butadiene styrene and polypropylene materials were used as base polymers. Using the results obtained from the experiments, moulding area diagrams were plotted for both runner systems with respect to the process parameters of injection pressure and melt temperature changing within a wide range. It was observed that the required injection pressure was considerably lower to produce samples with higher weight in the case of hot runner system. The shrinkage and warpage increased with increasing process temperature, decreased with increasing injection pressure, and occurred at low level when the sample weight was high.
Compression resin transfer molding process (CRTM) combines features of compression molding with traditional Resin Transfer Molding (RTM). The CRTM process is described in three stages, with resin being injected into the gap in Stage I, closing of the gap in Stage II and actual compression of preform and re-distribution of the resin in Stage III. To fabricate a void free part, one has to understand the resin flow during these stages. Governing equations for each stage are formulated, relevant non-dimensional parameters are derived and brief description of the numerical model is presented. Assembling the process parameters into non-dimensional groups significantly reduces the number of variables to be explored in the process. The paper analyzes the impact of the dimensional less parameters on impregnation time with the numerical process model. The results show that the impact of many parameters on process speeds is negligible, identifying two non-dimensional parameters that influence the resin injection.
This paper presents a simulation procedure for the mould-filling processes in which a field-analysis module of a general-purpose finite-element package is employed. The formulations used in this procedure are based on the finite element/nodal control-volume approach. The numerical concepts employed for modelling the effects of convective heat transfer on temperature and resin cure are discussed. Numerical implementation of the procedure is presented. The procedure was applied to simulate different mould-filling examples under isothermal and non-isothermal conditions. The results show that the simulation procedure developed is numerically valid and stable, and provides reasonably accurate predictions.
Silica fibre/phenolics composites produced by resin transfer moulding (RTM) solution impregnation technique are finding applications as aerospace structures. Typical phenolics contain solvent to facilitate injection and mould filling. It has been found that volatilisations of solvent and condensation polymerisation byproduct would cause void in cured composites, which is believed to affect the properties of the final product. In the present study, the role of solvent in the RTM impregnation process of silica fibre/phenolics composites was investigated. Experiments on wettability and flow were performed to evaluate the thermodynamical interaction on microscopic level occurring in fibre and resin system. Void content and interfacial strength were also examined. For the first time it has shown that the RTM process of silica fibre/phenolics composites is highly solvent dependent. Phenolics form distribution gradient in RTM mould with respect to isomeric composition under the effect of solvent, which results, to a varying extent, in the inhomogeneity of void content and thus interlaminar shear strength of the resulting product. The present work gives an insight into the role of organic solvent in RTM processing and this will help in choosing the best possible solvent for the solution impregnation system.
The effects of processing variables on the mechanical behavior and the void content of one-part epoxy based glass fabric composites produced by resin transfer molding (RTM) were investigated. The variables studied included injection pressure, injection temperature, and fabric structure. Image analysis was used to measure the void content in the composites. Variations in injection pressure and temperature were found to have a significant effect on the quality and the mechanical performance of composites. The optimized physical and mechanical performance of the composites was obtained by processing the resin at 160°C under 392 kPa pressure. Molding of highly permeable EF420 fabric required a shorter mold filling time, but resulted in reduced flexural strength and storage modulus in the resulting composites as compared with that of the composites containing 1581 fabric.
A general methodology to robust process optimization that incorporated several innovative strategies was developed and applied to the injection molding runner balancing problem. The variables were systematically perturbed according to a design matrix to simulate the effects of process variation, which were characterized by the extent that rejected parts violated the predefined tolerances. The runner balancing optimization problems were characterized by multiple objectives and constraints, which consider cost, product quality and sensitivity to process variation. The resulting problems were solved by optimizing the independent variables with a multi-objective genetic algorithm.For optimizations that varied the runner diameters, several robust solutions were identified which required larger runner system volumes, but were significantly less sensitive to the effects of process variation when compared to deterministic solutions. The key parameter was the diameter ratio between the secondary runners furthest from the injection point. Optimizations that varied the runner lengths in addition to their diameters significantly reduced the volume needed to balance a robust runner system, when compared to the results of optimizations that only varied the runner diameters.
Achievement of high class surface finish is important to the high volume automotive industry when using the resin transfer molding (RTM) process for exterior body panels. Chemical cure shrinkage of the polyester resins has a direct impact on the surface finish of RTM molded components. Therefore, resins with low profile additives (LPA) are used to reduce cure shrinkage and improve surface quality of the composite parts. However, little is known about the behaviour of low profile resins during RTM manufacturing and their ultimate effects on the surface quality of molded plaques. In this work, the effects of controlled material and processing parameters on the pressure variations, process cycle times and ultimately on the surface quality of RTM molded components were investigated. Taguchi experimental design techniques were employed to design test matrices and an optimization analysis was performed. Test panels were manufactured using a flat plate steel mold mounted on a press. Pressure sensors were inserted in the mold cavity to monitor pressure variations during different stages of cure and at various locations in the mold cavity. It was found that a critical amount of LPA (10%) was required to push the material against the mold cavity and to compensate for the resin cure shrinkage. A significant increase in pressure was observed during the later stages of resin cure due to the LPA expansion. The pressure increase had a significant effect on the surface roughness of the test samples with higher pressures resulting in better surface finish. A cure gradient was observed for low pressure injections which significantly reduced the maximum pressure levels.
In the resin transfer molding process, residual air in the pores of fiber preform results in dry spots and microvoids in the finished product. The dry spots are usually formed due to irregular permeability of fiber mat and improper injection locations. The microvoids result from non-uniform microarchitecture of the fiber preform, and they are transported through the gap between fiber tows during infiltration of the resin. In this study, a real-time simulation/control method was proposed to actively control the formation and the transport of air voids during the mold filling. The flow equations were solved in real time to predict the change of the flow front shape. The flow front was detected by optical sensors and the control actions were taken based on the sensor signals. Through this automated simulation/control scheme, a real-time control of resin flow could effectively avoid the dry spots and minimize the formation of microvoids by modulating the injection pressure.
In this study, a number of abhesion-promoting coatings were considered in terms of their physicochemical and release properties. The techniques used to further this study include; field emission gun scanning electron microscopy, atomic force microscopy (AFM), profilometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy, static secondary ion mass spectrometry, Fourier transform infra-red analysis and contact angle analysis for coating physical and chemical characterisation along with pulsed force mode atomic force microscopy (PF-AFM) and other adhesion and mechanical tests to determine surface release properties. These coatings were applied to metal substrates and were based upon silicone, fluoropolymer or metal-PTFE composite chemistry, all being potentially useful as release films for resin transfer moulding applications. The semi-permanent Frekote B15/710NC mould release coating system, which is based on PDMS, proved extremely effective in terms of release against a cured epoxide applied under pressure. Although fluoroalkylsilane coatings offer a number of technological advantages for release applications, they generally produce very thin coatings which conform to any existing surface topography and adhesion through mechanical interlocking. The commercial PTFE-based coatings were found to provide poor release properties due to the presence of surface microcracks which allowed epoxide penetration when cured under elevated pressure and temperature. Electroless Ni/PTFE composite coatings comprise a hard nickel-phosphorus matrix containing a very fine dispersion of PTFE particles. The matrix proved sufficiently robust for industrial applications and the low friction and surface energy provided by the embedded PTFE combined with macroscopic-scale surface roughness provided efficient mould release.