Resin Transfer Moulding Method Research Articles

An experimental study on ballistic limit: the effect of hole drilling on the mechanical properties of a polymeric composite plate produced by the resin transfer molding method

The high fracture strength and exceptional impact resistance of polymer-based composites are of paramount importance to various industries like aerospace, automotive, and construction. The resin transfer molding (RTM) process is used to produce composite samples of superior quality, minimal porosity, and reduced lamination defects. In the present study, the RTM method was employed to fabricate glass fiber-reinforced composites, aiming to investigate their specific mechanical properties and structural performance. The study initially determined the ballistic limit of the produced samples. Subsequently, experimental investigations were carried out to examine the impact of hole drilling on the tensile strength, flexural strength, and impact resistance of the samples. The results revealed that the produced polymer plate demonstrated a ballistic limit with a pressure of 11 bar and a speed of 104 m/s, leading to ball restriction in the plate. The sample without holes showed the highest fracture force, while samples with three and five holes exhibited reduced fracture forces. Additionally, bending force and impact resistance were lower in samples with multiple holes compared to the sample without holes. The impact resistance of the sample with five holes was the lowest among all configurations. The study revealed that the presence of three holes arranged in a row has a lesser impact on reducing the ultimate tensile force compared to the effect of five holes. Moreover, the bending test results indicated that sample failure occurred on the side under tension, resulting in higher bending forces than tensile forces.

Nonlinearity of mechanical behavior of 3D-reinforced composites under compression

Modern technological capabilities make it possible to produce 3D spatially-reinforced for polymer composite materials. The tasks of experimental research and analysis of the deformation process of new composite materials for aviation purposes taking into account the nonlinearity of mechanical behavior become actual. The paper presents an experimental study of the mechanical compression behavior of composite material specimens made of 3D woven carbon fiber preforms using the pressure impregnation technology (Resin Transfer Molding method with a pairwise interlayer reinforcement and a longitudinal layer). Compression mechanical tests were carried out on specimens using a universal system of electromechanical testing Instron 5882 and a system of 3D analysis of displacement and strain fields on the surface. Tests were conducted in accordance with ASTM D 3410 recommendations and using specialized tooling. Consideration of nonlinearity parameter during experimental data processing is proposed. The importance of determining the values of critical deformation in compression as a parameter characterizing the moment of the beginning of fracture is noted. Comparison of carbon fiber composite materials made by the same technology from fibers and binders of different manufacturers has been carried out. The experimental diagrams "stress-strain" and their approximating dependences taking into account the nonlinearity function w are obtained. The type of functions w of the studied materials is defined, the linear approximation of dependence of functions w on deformation is substantiated. Values of strength limits, elastic modulus, nonlinearity coefficient and critical damage were obtained, statistical processing of the obtained results and their analysis were carried out.

Study on Curing Deformation of Composite Thin Shells Prepared by M-CRTM with Adjustable Injection Gap.

A composite thin shell with a high fiber volume fraction prepared by resin transfer molding (RTM) may have void defects, which create deformations in the final curing and lead to the final product being unable to meet the actual assembly requirements. Taking a helmet shell as an example, a multi-directional compression RTM (M-CRTM) method with an adjustable injection gap is proposed according to the shape of the thin shell. This method can increase the injection gap to reduce the fiber volume fraction during the injection process, making it easier for the resin to penetrate the reinforcement and for air bubbles to exit the mold. X-ray CT detection shows that the porosity of the helmet shell prepared by the newly developed technology is 36.6% lower than that of the RTM-molded sample. The void's distribution is more uniform, and its size is decreased, as is the number of voids, especially large voids. The results show that the maximum curing deformation of the M-CRTM-molded helmet shell is reduced by 13.7% compared to the RTM molded sample. This paper then further studies the deformation types of the shell and analyzes the causes of such results, which plays an important role in promoting the application of composite thin shells.

Flexural and Viscoelastic Properties of FRP Composite Laminates under Higher Temperatures: Experiments and Model Assessment.

This study investigates an experimental and analytical study on the flexural, failure, and viscoelastic properties of hybrid and non-hybrid composite laminates at increasing temperatures and frequencies. Carbon, glass, and hybrids of the two fibre materials with stacking sequences of [0/90]s were considered, and specimens were prepared via the resin transfer moulding method. Three-point bending and dynamic mechanical analysis tools were used. The failure surfaces of the laminates were examined using a scanning electron microscope. The results indicated that the flexural strength, modulus, and strain at failure of all groups of laminates decreased as the temperature increased. In particular, the storage modulus, damping factor, flexural strength, and flexural modulus properties of all groups of laminates increased as the hybrid ratio decreased on each targeted temperature and frequency test. However, the strain at failure increased as the hybrid ratio increased. Additionally, results obtained from the scanning electron microscope images confirmed that combinations of delamination and debonding failure modes were observed on the stacking sequences of [0]s and [90]s layers of bidirectional laminates. Finally, a comparison between the storage modulus results of all groups of laminates was conducted with three empirical models. The empirical model developed by Gibson et al. provided the most accurate prediction for all groups of laminates in the targeted temperature and frequency range. The predictions using the remaining empirical models were broadly similar. Further work is needed to optimise the empirical parameters and minimise the errors.

Influence of Pressure and Temperature on the Strength Properties of a Laminate Produced by the RTM Method

Abstract This paper discusses the effect of pressure on the content of microvoids and defects inside laminates fabricated under different pressures, by vacuum methods. Two basic vacuum methods resin transfer molding (RTM) and vacuum bag method were used in this paper. A glass mat with an alignment angle of (0□/90□) and a mass of 450 g/cm2 was used to produce the laminate, and a polymer resin was used as the matrix. Special attention was paid to the technological parameters of both processes. A mathematical analysis of the most important parameters which include flow rate, permeability, and gelation temperature has been carried out. In addition, the resin temperature is used to reduce the viscosity of the resin to facilitate its flow through the reinforcement, and in the final stage of production to control the chemical reactions occurring in the mold. The pressure is chosen so that the resin flow is continuous. The synchronization of these two parameters and the measurement of the time in which they occur are called the “cure cycle”. In the final step of the study, the composite was subjected to a static tensile test, using specimens of two different dimensions (scale effect) to evaluate the effect of microvoids and microcracks created by the processes on the strength of the material.

RESIN FLOW SIMULATION DURING THE RTM METHOD OF COMPOSITES PRODUCTION

Processes of plastic injection molding are often under analyzes in industry and science. Many of these considerations apply to epoxy resins with additional reinforcement, often with glass or carbon fiber inside the closed mould. The simulations of injection molding processes in the production of composite elements is not as common, as thermoplasts. Hence the idea to carry out the work described in this article. The RTM (Resin Transfer Molding) method is dedicated to serial production with the possibility of producing visual carbon fiber elements for aesthetic reasons. Simulations can help to better refine the products. This allows to take appropriate precautions and solve many issues before implementation. The article presents possible situations that could occur in real conditions. Various shapes models were prepared as basis of the numerical calculations. The analyses highlighting the possible issues were performed. The influence of resin pressure and flow rate on the final product was also considered. The aim was to present the characteristic phenomena and their causes that often occur in reality to technologists working with the RTM. Conclusions related to the work carried out are included. Based on the analyzes and conclusions drawn, it is possible to improve the quality of production processes.

Utilization of tyre rubber hybrid with ceramic and wood for impact energy absorption application

The used tyre rubber, scrap ceramic tiles and wood dust are largely dumped into landfills, which create environmental pollution to the surrounding. The recycling of tyre rubber is very limited, but it has good property to absorb the impact energy. Hence, these materials are used to prepare the composite in the present work. Composite materials were prepared by the resin transfer moulding method with different weight percentage of particles. The tensile, flexural and impact strength of composite specimens were compared with other combination of composites and also with the neat resin sample specimen. The tensile and flexural strength of composites were decreased with the addition of the rubber. But, the rubber particle with the ceramic in the resin matrix increases the impact strength of composite by 45.91% when compared with the neat resin sample. The addition of rubber enhances the impact strength of composite materials with all the combination of particles. The better distribution and good interfacial adhesion of particles with a resin matrix along the fractured surface were observed by the scanning electron microscope. And also, the nature of failure was identified by morphological studies.

Development and auxetic characterization of 3D composites produced with newly-designed multi-cell flat-knitted spacer fabrics

The paper deals with development and characterization of 3D sandwich composite structures reinforced with newly-designed multi-cell flat-knitted spacer fabrics in terms of compressive behaviour and Poisson’s ratio. Multi-cell spacer knitted preforms was produced on a computerized flat knitting machine. 3D composite samples with three different cross-sectional geometries were prepared via vacuum assisted resin transfer moulding method. Quasi-static compressive experiments were carried out on the prepared 3D composite samples. The Poisson’s ratio of re-entrant 3D knitted composite varied between -6 and -1, which clearly points to existence of auxetic behaviour of the samples. The re-entrant 3D composites also demonstrated the highest initial slope and area under the compression force-displacement curve than spear-head or hexagonal composite structures which refer to higher energy absorbing capacity. The Poisson’s ratio of 3D regular hexagonal knitted composites at small strain was usually 4 which gradually decreased to 1.6 as the exerted compressive strain increased. Additionally, 3D spear-head knitted composite having zero Poisson’s ratio was also developed.

Improving four-point bending performance of marine composite sandwich beams by core modification

The aim of this study was to improve four-point bending performance of foam core sandwich composite beams by applying various core machining configurations. Sandwich composites have been manufactured using perforated and grooved foam cores by vacuum-assisted resin transfer moulding method with vinyl-ester resin system. The influence of grooves and perforations on the mechanical performance of marine sandwich composite beams was investigated under four-point bending test considering the weight gain. Bending strength and effective bending stiffness increased up to 34% and 61%, respectively, in comparison to a control beam without core modification. Analytical equations were utilised for calculating the mid-span deflection, equivalent bending stiffness and ultimate bending strength of the sandwich beams. Finite element analysis was also performed to analyse the flexural response of the specimens taking into account the combined effect of orthotropic linear elasticity of the face sheet and the non-linear behaviour of the foam core.

Tensile-tensile Fatigue Behavior of Multi-axial Warp-knitted Reinforced Composite

An experimental study was carried out on the fatigue behaviour of multi-axial warp-knitted fabric composites. Composite samples reinforced with multi-axial warp-knitted fabric/matrix were manufactured by the vacuum-assisted resin transfer moulding method. Tensile-tensile fatigue cycling was carried out at different load levels, and S-N curves, tensile stress-strain curve and stiffness degradation of the multi-axial composite samples were obtained. Finally post-fatigue tensile tests were done at a stress level of 75%, at the stages of 1/3N and 2/3N, and the equivalent residual strength and stiffness degradation were obtained.

Effect of fiber densities on impact properties of biaxial warp-knitted textile composites

In this study, an appropriate fabric weight content controlled by the density of the warp and weft fibers is determined for biaxial warp-knitted composites referring to mechanical test results. Six different types of composite panel with two different fabric weights (813 and 1187 gr/m2) and with three different stacking sequences [90we/0wa/90we/0wa]s, [90wa/0we/90wa/0we]s, and [90wa/0we/90we/0wa]s are fabricated by using Resin Transfer Molding method. Having produced composite panels, drop weight impact tests are conducted on specimens. Microstructural characterization of impact tested materials is performed using optical microscope. The results of this study reveal that composites with biaxial warp-knitted preforms with lower weft and warp fiber densities (thin-ply) could absorb higher impact energies compared to those with higher weft and warp fiber densities (thick-ply).

Influences of clay and manufacturing on fire resistance of organoclay/thermoset nanocomposites

The organoclay GFRP nanocomposites are prepared using the vacuum assisted resin transfer moulding method. Two grades of organophilic clay with three content levels, three types of thermosetting resins (polyester, vinyl ester and epoxy), and three nanoclay dispersion techniques are investigated. To understand the effects of these factors on the fire performance, Taguchi design of experiments (DoE) method is employed and preferred combinations of factors are determined using a one-step and a proposed two-step GLM ANOVA. The one-step ANOVA is applied directly on the experimental results, while the two-step ANOVA is conducted on the signal-to-noise ratios obtained from the Taguchi analysis. The combination of mechanical and ultrasonic dispersing procedure has been found to have considerable influence on the of nanoclay distribution. While both approaches provide insights into the influences of each fabrication factor, the two-step gives a better prediction of the favourable response combination for the nanocomposites when validated with experiments.

Evaluation of Mechanical Properties of Hybrid Fiber Reinforced Polymer Composites and their Architecture

Traditional fiber reinforced polymer (FRP) composite that is often fabricated from single type of reinforcement has shown its ability to replace the conventional metallic material counterparts. However, due to several stringent requirements on ductility, this has affected the performance of FRP composites for the structural applications. Therefore, hybrid composites, which combine two or more fiber reinforcements, have been introduced in order to overcome the short of traditional FRP composites. This paper investigates the mechanical properties of three different arrangements of hybrid composites made from glass fiber (plain-woven and stitched bi-axial ±45˚) and plain-woven carbon fiber. Vacuum assisted resin transfer moulding method was employed to fabricate the hybrid composite panels. Mechanical properties such as tensile strength, flexural strength and volume fraction of the hybrid composites were determined per ASTM standards. Experimental results indicate that the [CWW]6 arrangement, where C and W are weaved carbon fiber and glass fiber respectively, were superior in terms of mechanical properties.

Evaluation of Interlaminar Shear Strength of Longitudinal GRP Railway Bogie Frames Considering Microstructure Aspects

The paper contains results of a comprehensive research and development programme aimed at an evaluation of static strength of a GRP railway bogie of a new advanced design. The works were carried out as one of the essential phases of the implementation of a EUREKA project EUROBOGIE, which is aimed at development of advanced vehicle bogies and has a great potential to lead to more efficient movement of freight and passengers with lower environmental impact. The GRP bogie design consists of three main load carrying parts, namely two quite massive longitudinal side frames connected by a central transom plate which are manufactured in a single moulding operation using the resin transfer moulding (RTM) method. Since the component is unusually thick, all parameters of the RTM method have to be well balanced. One of the critical issues in the design and manufacture is the connection area of the transom with the side frames. Therefore, testing of this subcomponent was an important part of the bogie development. Results of the experimental programme provided necessary feedback for the optimization of the manufacture technology.

Effect of thread tension on mechanical performance of stitched glass fibre-reinforced polymer laminates –experimental study

This article presents the results of interlaminar shear and flexural tests of polyester resin – glass fibre laminates made from the preforms unstitched and stitched by various thread tensions: low, medium and high. The laminates were impregnated using resin transfer moulding method. The interlaminar shear and flexural tests were conducted by loading parallel and transverse to the stitch lines. Interlaminar shear strength, flexural strength and flexural modulus were obtained. Deformation extent of the reinforcing structure of the stitched laminate increases with the increase in the thread tension and causes decrease in the flexural strength and modulus. However, the increase in the thread tension offers improvement in the interlaminar shear strength. Optimization of changes in the flexural properties and the interlaminar shear strength with the thread tension showed that an operation of stitching of the reinforcing preforms should be conducted by low or medium stitching thread tension (approximately 3–9 N).

Manufacturing and structural behavior evaluation of composite side beams using autoclave curing and resin transfer moulding method

In this study, in order to replace the conventional steel bogie with a composite bogie, a composite side beam made of glass/epoxy was developed to be used in the bogie frame of an urban subway train. The composite side beam was manufactured using two different manufacturing method; autoclave curing method and resin transfer moulding method (RTM). And, then, they were tested under a vertical load of 140 kN to evaluate the structural behavior. Moreover, the stress and strain distribution was evaluated with the finite element method and compared with the experiment. The maximum deflections of the two side beam were 7.74 mm and 8.25 mm, respectively. The side beam made by RTM appeared a little softer than the autoclave cured one due to the lower fiber volume fraction. Through the parametric study for the different design parameters, it was known that the variation of the side beam height appeared to be strongest effect to deflection.

Numerical and Experimental Evaluation of Dispersion Coefficient for Resin Transfer Modeling

Resin transfer molding (RTM) is a composite manufacturing process. A preformed fiber is placed in a closed mold and a viscous resin is injected into the mold. In this article, a model is developed to predict the flow pattern, extent of reaction, and temperature change during the filling and curing in a thin rectangular mold. A numerical simulation is presented to predict the free surface and its interactions with heat transfer and cure for flow of a shear-thinning resin through the preformed fiber.To simulate this process, using local thermal equilibrium assumption, it is essential to include the thermal dispersion term in energy equation. The best method to achieve this result is experimental simulation and preparing proportionate system at simple conditions without curing. By comparison of recorded temperature values (using installed instruments at various locations), and the corresponding results from numerical solution for different estimated values of dispersion coefficient, this coefficient has been evaluated based on the best matching estimate. The results show that, to simulate composite manufacturing process by RTM method, the effect of dispersion term in energy equation shall not be neglected.

An investigation of bending fatigue behavior for glass-fiber reinforced polyester composite materials

To investigate bending fatigue behaviors for glass-fiber reinforced polyester composite material, 800 g/m 2, 500 g/m 2, 300 g/m 2, and 200 g/m 2 glass-fiber woven and 225 g/m 2, 450 g/m 2, and 600 g/m 2 randomly distributed glass-fiber mat samples with polyester resin have been used. The samples have been produced by the RTM (Resin Transfer Molding) method and the samples have been cut down with directions of 0/90°, ±45°. As results of the combinations from the samples, nine different structures has been obtained. Furthermore, a new mold have been designed for the RTM method. To provide a full infiltration (wetting) of fibers, a simple method has been applied in this new mold system. A new computer aided and multiple-specimen test apparatus have been designed and constructed to simulate load and stress behavior of axial fan blades on the wind tribunes. This multiple specimen apparatus has a big advantage to shorten test time and to test 16 specimens at the same time. Firstly, composite specimens have been applied to the three-point bending test. Later, fatigue tests have been carried out. For the bending fatigue test, “fixed stress” fatigue type has been used. To determine the fatigue limit of all the specimens, S–N diagrams (Wöhler plots) have been derived from experimental results. According to the test results, the highest fatigue life has been obtained from 800 g/m 2 fiber glass woven specimens with 0/90° (group E). The property of anisotropy of the GFRP (Glass Fiber Reinforced Plastic) material is dominant on the fatigue strength which has been clearly observed from the experiments. In the test results, the effective parameters are density of fiber distribution on the area, fiber angle, resin permeability of woven fiber, full infiltration (wetting) or without infiltration of fibers.

Glass-fibre-reinforced composites with enhanced mechanical and electrical properties – Benefits and limitations of a nanoparticle modified matrix

Nanoparticles and especially carbon nanotubes (CNTs) provide a high potential for the modification of polymers. They are very effective fillers regarding mechanical properties, especially toughness. Furthermore, they allow the implication of functional properties, which are connected to their electrical conductivity, into polymeric matrices. In the present paper, different nanoparticles, as fumed silica and carbon black, were used to optimise the epoxy matrix system of a glass-fibre-reinforced composite. Their nanometre-size enables their application as particle-reinforcement in FRPs produced by the resin-transfer-moulding method (RTM), without being filtered by the glass-fibre bundles. Additionally, an electrical field was applied during curing, in order to enhance orientation of the nanofillers in z-direction. The interlaminar shear strengths of the nanoparticle modified composites were significantly improved (+16%) by adding only 0.3 wt.% of CNTs. The interlaminar toughness G Ic and G IIc was not affected in a comparable manner. The laminates containing carbon nanotubes exhibited a relatively high electrical conductivity at very low filler contents, which allows the implication of functional properties, such as stress–strain monitoring and damage detection.