Papers by Keyword: RTM

Abstract: The lightweight potential of components made of fiber-reinforced plastic can be enhanced by use of sandwich composites. So far, limited dynamic properties of plastic-based foams have prevented the use of sandwich composites in machine applications. The combination of closed-cell aluminum foam (ALF) and carbon fiber reinforced plastic (CFRP) provides a solution to this obstacle. Aluminum foam is characterized by favorable damping properties with minimum weight and CFRP provides high strength and stiffness at similarly low density. This paper deals with the design of a hybrid sandwich composite and its interpretation by using customized FEM simulations.Producing this kind of a sandwich composite in an economic production process presents a major challenge. Thus, a method has been developed that prevents excessive penetration of the resin into the pores of the aluminum foam. A high volume fraction of the resin in the foamed sandwich core would increase density and negatively influence damping properties. The implementation of a barrier layer will avoid this penetration. A DoE was developed and RTM process parameters were varied with the objective of achieving the highest specific bending stiffness. In preliminary experiments the appropriate range of injection pressure, mold temperature, and pressure force was determined. Tests with a nonwoven fabric could prevent the resin from infiltrating into the aluminum foam. Mechanical properties of the sandwich composite are only marginally affected.A model was developed to calculate the obtainable sandwich composite properties. The calculation method considers both the characteristics of the aluminum foam and the CFRP anisotropy. Based on this model a reliable calculation of the applied load could be accomplished. The design of the sandwich composite was targeting at high stiffness and determination of the natural frequency. Parallel to calculations, tests on specimen were performed and the obtained results were included into the calculation as part of the material model.

Abstract: In this study, an investigation on mechanical properties of flax/vinyl ester natural fiber composite was performed. Vacuum Assisted Resin Transfer Molding (VARTM) manufacturing method was adopted for manufacturing the flax fiber composite specimen. The mechanical properties of the manufactured flax composites were compared with flax composite data cited from some references. Based on this, the experimental data showed that the flax/vinyl ester composite has some advantages when it is applied to environment-friendly structure.

Abstract: This paper uses FLOTRAN to estimate the resin flow permeability of fiber tow in RTM. Nine models of different fractions varies from 0.4~0.75 have been built, and the random process of the fiber’s distribution is realized by APDL code. The results show that the dispersion of fiber determines the fluid flow channels, which effect the pressure and velocity’s distribution; the FLOTRAN can be used to estimate the transverse permeability of the fiber bundles.

Abstract: This work aims to investigate the infiltration of a CaCO₃ filled resin using experiments and the PAM-RTM software. A preform of glass fiber mat, with dimensions 320 x 150 x 3.6 mm, has been used for experiments conducted at room temperature, with injection pressure of 0.25bar. The resin contained 10 and 40% CaCO₃ content with particle size 38μm. The numerical results were evaluated by direct comparison with experimental data. The flat flow-front profile of the rectilinear flow was reached approximately halfway the length of the mold. It was observed, that the speed of the filling decreases with increasing CaCO₃ content and,the higher the amount of CaCO₃ in the resin, the lower the permeability of the reinforcement that is found. The reduction in permeability is due to the presence of calcium carbonate particles between the fibers, hindering the resin flow in the fibrous media. The computational fluid flow analysis with the PAM-RTM proved to be an accurate tool study for the processing of composite materials.

Abstract: Resin Transfer Molding (RTM) is one of the most widely known composite manufacturing techniques of the liquid molding family, being extensively studied and used to obtain advanced composite materials comprised of fibers embedded in a thermoset polymer matrix. Nowadays, RTM is used by many industrial sectors such as automotive, aerospace, civil and sporting equipment. Therefore, the objective of this study is to verify the effect of calcium carbonate mixed in resin in the RTM process. Several rectilinear infiltration experiments were conducted using glass fiber mat molded in a RTM system with cavity dimensions of 320 x 150 x 3.6 mm, room temperature, maximum injection pressure 0.202 bar and different content of CaCO₃ (10 and 40%) with particle size of 75μm. The results show that the use of filled resin with CaCO₃ influences the preform impregnation during the RTM molding, changing the filling time and flow from position, however it is possible to make the composite with a good quality and low cost.

Abstract: In order to evaluate the feasibility of resin composite process, firstly analysis of the properties of the composite and the RTM molding, autoclave molding process. This paper presents the content of the evaluation: the evaluation index system was established according to the evaluation content. Through the analysis of product features, composite material forming method, manufacturing resources, to product manufacturability, cost of production, production cycle, taking hierarchical method to construct a fuzzy tree based on hierarchical multi objective evaluation system model. Using 1~9 ratio method for the membership of specific indicators under this model, discussed the problem of weight distribution, and verifies the feasibility of this method by the example analysis, to realize the optimization of composite material molding method.

Abstract: In order to eliminate the bubbles during composites manufacturing, a special performance was designed. And the effects of the speed of the resin injection on bubble content were investigated. The results demonstrate that the speed of resin injection has distinct effects on the bubble content. When the speed of resin injection is slightly higher than the speed of capillary injection, the bubble content of the test pieces with latitudinal fiber bundles is more than the test pieces without latitudinal fiber bundles. But when the speed of the resin injection is slower than the speed of capillary injection, the bubble content of the test pieces with latitudinal fiber bundles is less than the test pieces without latitudinal fiber bundles. These results will provide a reference for the design of RTM process parameters.

Abstract: A novel semi-prepreg resin transfer molding (RTM) process was developed to address difficulties associated with RTM process and to improve the mechanical properties of the resulting composites. Unidirectional semi-prepregs exhibiting relatively good overlay characteristics were prepared via prepolymerization of bismaleimide resin followed by wet winding. The processing characteristics and mechanical properties of composites fabricated via semi-prepreg RTM technology were compared with those of composites produced using a normal-prepreg compression molding process. Experimental results showed that the laminates fabricated by the semi-prepreg RTM process were of better internal quality and had superior mechanical properties as compared with laminates fabricated by the normal-prepreg compression molding process.

Abstract: In the processing of high performance composite materials, the RTM process has been widely used by many sectors of the industry. This process consists in injecting a polymeric resin through a fibrous reinforcement arranged within a mold. In this sense, this study aims to simulate the rectilinear infiltration of pure resin and filled resin (40% CaCO₃) in a mold with glass fiber preform, using the PAM-RTM commercial software. Numerical results of the filling time and fluid front flow position over time were assessed by comparison with the experimental data and a good accuracy was obtained.

Abstract: Composite material can be defined as a combination of two or more materials on a macroscale to form a useful material, often showing properties that none of the individual independent components shows. Resin Transfer Molding (RTM) is one of the most widely known composite manufacturing technique of the liquid molding family, being extensively studied and used to obtain advanced composite materials comprised of fibers embedded in a thermoset polymer matrix. This technique consists in injecting a resin pre-catalysed thermosetting in a closed mold containing a dry fiber preform, where the resin is impregnated. The aim of this study is to investigate the effect caused by the use of CaCO₃ filled resin on the characteristics of the RTM process. Several experiments were conducted using glass fiber mat and polyester resin molded in a RTM system with cavity dimensions of 320 x 150 x 3.6 mm, at room temperature, and different CaCO₃ content (0, 10, 20, 30 and 40% in weight). The results show that the use of filled resin with CaCO₃ influences the resin viscosity and the porous media permeability, making it difficult to fill the porous media during the molding process, however it is possible to make composite with a good quality and low cost.