Resin Transfer Molding Process Research Articles

Finite element modelling of non-isothermal curing kinetics for resin transfer moulding process

The numerical modelling and simulation of empirical cure rate models presented for the non-isothermal resin transfer moulding curing process cycle. The nth order model, Kamal and Sourour’s (K & S) model and their modified forms used to study the efficacy of Comsol multi-physics simulator without adding any user defined program. The appropriate value of mould temperature selected from the isothermal curing simulation of nth order model. The transient variation of degree of cure and temperature within the saturated preform has been presented. It has been observed that the models having two rate constant were not converging for the initial temperature lower than 315 K. Therefore, for the sake of uniformity we used initial temperature as 315 K for all the models and mould temperature as 380 K. Although, process cure time was less for K & S model, we observed the large temperature gradient inside the composite plate for the two rate constant models. To add on the complexity in the simulation three dimensional curved plate is simulated for 10 mm, 20 mm and 30 mm thickness. Definitely, with increase in thickness of the composite plate, the time to complete the cure reaction is increased.

An experimental and simulation-based analysis of resin flow front during fabrication of lightweight composite components using VARTM process

Vacuum assisted resin transfer moulding process is gaining attention in different sectors for lightweight polymer matrix composites. This article is focused on the determination of the permeability of the manmade reinforcements with a rectilinear method. In the rectilinear method, the permeability was determined using a tracked flow front during the resin infusion process. The composite fabrication was carried out using three reinforcements. The permeability was determined for five different stacking sequences viz. C-12, G-12, A-12, (CGA)4 and (C2G2A2)2. For a similar experimental condition, a simulation study was performed using ANSYS fluent. In a transient mode simulation, the permeability results were used as input for the flow front simulation. From the experimental and simulation approach, it was found that as the permeability increases the mould filling time is decreases. The comparison of the simulation and experimental data of the flow front is reported in the present article.

A Conceptional Approach of Resin-Transfer-Molding to Rosin-Sourced Epoxy Matrix Green Composites

In this concept-proof study, a preform-based RTM (Resin Transfer Molding) process is presented that is characterized by first pre-loading the solid curing agent onto the preform, and then injecting the liquid nonreactive resin with an intrinsically low viscosity into the mold to infiltrate and wet the pre-loaded preform. The separation of resin and hardener helped to process inherently high viscosity resins in a convenient way. Rosin-sourced, anhydrite-cured epoxies that would normally be regarded as unsuited to liquid composite molding, were thus processed. Rheological tests revealed that by separating the anhydrite curing agent from a formulated RTM resin system, the remaining epoxy liquid had its flowtime extended. C-scan and glass transition temperature tests showed that the preform pre-loaded with anhydrite was fully infiltrated and wetted by the liquid epoxy, and the two components were diffused and dissolved with each other, and finally, well reacted and cured. Composite laminates made via this approach exhibited roughly comparable quality and mechanical properties with prepreg controls via autoclave or compression molding, respectively. These findings were verified for both carbon and ramie fiber composites.

The method of RTM process modeling using porous medium

This paper proposes a method to simulate the Resin Transfer Molding process by using Ansys Fluent software. The offered approach permits to calculate impregnation time, to predict dry zones after impregnation and proposes a method to calculate porosity of the final product to predict the mechanical properties. The method is illustrated in the plate resin impregnation case.

Prediction and compensation of process-induced distortions for L-shaped 3D woven composites

A physics-based numerical model for prediction and compensation of the process-induced distortion of 3D woven composite (3DWC) is presented. A new tool-part interaction modelling method for the Resin Transfer Molding process is developed, in which the nonlinear material properties and non-thermoelastic distortion are taken into account. Flat and L-shaped 3DWC parts were fabricated and the process-induced distortions were evaluated. Adopting the input values determined by the warpages of flat parts, the spring-in of L-shaped parts predicted by the model is consistent with the experimental measurements. Based on the model, it is found that taking the warpage/spring-in of the uncompensated parts as the compensation value will result in a deviation between the manufactured parts and the nominal shape. An improved comprehensive compensation procedure is proposed and applied to an L-shaped 3DWC part. The result shows that the dimensional precision of the part can be significantly improved by the compensation process.

Low velocity impact on pre-loaded composite plates: A novel standard-based experimental apparatus

Despite composite materials presenting a viable design solution for structural weight savings, their low resistance to impact damage portraits a potential drawback. This work presents a study on the compressive pre-loading effects on Low Velocity Impact, LVI, for composite laminated plates. Despite the absence of a standard testing procedure accounting for pre-load effects, a test rig was designed specifically for LVI on pre-loaded plates while preserving ASTM D7136M-15 guidelines for the stress-free specimens. Woven fabric composite laminated plates were manufactured using the Resin Transfer Moulding (RTM) process and subjected to impact on pre-loaded conditions. Three pre-load levels were prescribed, representing conditions ranging from low strain levels until post buckling regime. FE numerical models were implemented in ABAQUS FE code, comparing different Continuum Damage Mechanics (CDM) constitutive model formulations with experimental results. Analytical and numerical predictions showed good correlation with experimental results, allowing for further application of the test apparatus and methodology.

Deep learning for impact detection in composite plates with sparsely integrated sensors

In this paper, both location and energy of impacts on an anisotropic carbon fiber reinforced plate (CFRP) are detected with the help of deep learning. We introduce sparse low-cost sensor array integration in CFRP plates that allows for structural monitoring of lightweight structures. Using a resin transfer moulding process microelectromechanical systems (MEMS) and piezoelectric transducers (PZT) sensors are integrated into CFRP plates. We developed an automated test bench to perform weight drop impact loadings with impact energies ranging between 0.22–0.56 mJ on a 1 × 1 cm2-grid with 441 locations. The obtained sensor signals were processed by means of a short-time fourier transformation and used as input for the training of a deep learning model. This model was implemented with a convolutional neural network. To accelerate the training phase we introduce a coarse analytical model that generates artificial sensor signals we use for pretraining of the neural network. Yielding high prediction accuracies of 99.82% and 98.68% for a correct classification of impact location and energy, respectively, the capability of the proposed approach was demonstrated. Despite their limited resolution the low-cost MEMS accelerometers were able to correctly locate an impact and its energy with 99.76% and 97.04%, respectively. The pretraining led to an increased robustness of the training process. Additionally, for the case of PZT sensors, it also reduced the number of required epochs for convergence significantly.

Multi-scale modeling of distortion in the non-flat 3D woven composite part manufactured using resin transfer molding

This paper presents a multi-scale thermo-chemo-mechanical simulation predicting the distortion of a 3D woven composite part manufactured using the Resin Transfer Molding (RTM) process. The multi-scale numerical procedure relied on an anisotropic temperature- and degree of cure-dependent viscoelastic constitutive law whose parameters were obtained from experimental data and a blackbox optimization algorithm. Analytical (at the micro-scale) and numerical (at the meso-scale) homogenization procedures were used to compute the effective coefficients of thermal expansion and chemical shrinkage. An actual 3D woven non-flat composite specimen exhibiting variations in properties and thickness was designed and manufactured using the RTM process. The contoured geometry of the manufactured part was digitized using an industrial optical 3D scanner and compared against the developed multi-scale numerical predictions. It was found that the presented approach was capable of qualitative and, in some cases, quantitative prediction with the highest accuracy ~2.8% of manufacturing induced geometrical distortions.

WITHDRAWN: Flexural property evaluation of foam core sandwich panel with carbon/kevlar epoxy hybrid facesheets

Abstract The Sandwich composites are extensively used in transportation, aerospace, marine and sports equipment industries. These types of composites are used because of the superior flexural properties exhibited over the monolithic laminates without any substantial addition in weight of the construction. The hybrid sandwich composites are a novel variety of composite sandwich materials which uses different reinforcement in the facing sheet or in the core. The hybrid composites are employed where tailor made properties are needed like combination of impact and flexural strength is desired. This paper describes the manufacture of hybrid plain weave fabric carbon/kevlar face sheet foam core sandwich panels of monolithic Type-I [C/C/Foam/C/C], Type-II [K/K/Foam/K/K], Type-III interply [C/K/Foam/K/C], Type-IV [K/C/Foam/C/K] and Type-V intraply [H/H/Foam/H/H] using Vacuum Assisted Resin Transfer Molding (VARTM) process. The hybrid specimens were subjected to experimental - three point bending test and compared with the monolithic face sheet sandwich specimens. Comparing the interply Type-IV [K/C/Foam/C/K] and Type-III [C/K/Foam/K/C] sandwich panel intraply panel there is a maximum bending load carrying capacity enhancement of 46.10% and 62.84% increase when compared with the Type-V [H/H/Foam/H/H] sandwich panel respectively. Excellent correlation is observed in the comparison of analytical expressions for peak load to the experimental plots.

A fully coupled thermo-mechanical analysis for the minimisation of spring-in and process time in ultra-thick components for wind turbine blades

The paper tackles the multi-objective optimisation of the cure stage of the Vacuum Assisted Resin Transfer Moulding (VARTM) process to manufacture the root insert of wind turbine blades. The aim of the study is to compare the Pareto front obtained from a pure heat transfer analysis, where temperature overshoot is an objective, with the one achieved when a coupled thermo-mechanical analysis is used, in which spring-in deflection is directly addressed. The optimisation methodology links the finite element solution of a heat transfer and a coupled thermo-mechanical problem of the cure process with a genetic algorithm suitable for multi-objective problems. The paper highlights that whilst minimising overshoot temperature is effective in reducing the spring-in, optimal design points might remain hidden. Furthermore, by showing the evolution of transverse residual stresses the paper suggests that designing cure cycles that introduce compressive stresses before vitrification is beneficial to counteract the subsequent tensile stresses generation.

A Bayesian belief approach to quality control of resin transfer molding process

In recent years, there has been a significant global shift towards use of polymer matrix composite materials in a wide range of industries, including aerospace, automotive, marine, and sports, among others. Despite the rapid uptake and widespread adoption of this material technology, there are still technical challenges faced daily by manufactures due to the inherent complexities of different composite processing techniques. This paper aims at establishing a new scheme for better quality control management of resin transfer molding (RTM) processing for thermosetting composites, using a Bayesian belief network (BBN). The data were collected through knowledge engineering among the manufacturing experts with the help of real-life application history. A total of 13 governing factors for the RTM process, which would theoretically have a role on the final product quality, were identified. The sensitivity analysis of the BBN showed that the major contributing factors of the quality are the resin viscosity profile, part design features, resin cure peak temperature, and reinforcement permeability. The conditional probability tables were constructed using a quality index from industrial experts, and the causal relationships captured by the BBN were built using knowledge engineering. It is also shown how the basic BBN model can be further updated by integrating the interaction weights between the attributes that define the product quality.

A numerical modelling for resin transfer molding (RTM) process and effective thermal conductivity prediction of a particle–filled composite carbon–epoxy

The objective of this paper is to develop a global modelling approach, that simulates both the resin transfer molding (RTM) manufacturing and the prediction of the effective thermal conductivity (ETC) of a carbon–cpoxy (CE) laminated composite reinforced with particles. This numerical approach is based on two main stages. First, a numerical simulation of the suspension flow and the filtration of the charges during the RTM process. A method, for simulating the flow of a resin, loaded with particles in suspension through a fibrous medium, considering its double porosity scale, has been proposed. It is based on the description of the flow by Stokes–Darcy coupling, filtration phenomenon and particle dynamics. Secondly, the ETC of the composite thus produced is evaluated using a numerical homogenisation technique, considering the spherical particles inserted into the carbon–epoxy laminated composite. These obtained results have shown that, the incorporation of particles in the laminated composite leads to a significant increase in their effective thermal conductivity, which depends on their thermal conductivity. Finally, a simple linear thermal model has been proposed to predict the effective thermal conductivity of the composite carbon–epoxy–particles, as a function of that of the base composite carbon–epoxy and that of the particles.

Multiscale numerical and experimental investigation into the evolution of process-induced residual strain/stress in 3D woven composite

The process-induced residual strain and stress have a significant impact on the forming quality and service performance of 3D woven composites (3DWC). A multiscale model of 3DWC is developed to predict the residual strain and stress after the manufacturing process. Representative volume element at fiber scale and yarn scale are developed according to the geometric characteristics of 3DWC, and the modulus-development model is developed with respect to finite element based micromechanics method. An equivalent temperature load method is proposed to develop the cure shrinkage strain model. A thermal-chemical-mechanical coupling analysis of 3DWC curing process is carried out by integrating the abovementioned models, and the evolutions of temperature, degree of cure and residual strain/stress are obtained. Fiber Bragg Grating sensors are hybridized into the fabrics before Resin Transfer Molding (RTM) processing. The signal from sensors during RTM shows that the residual strain evolution is in good agreement with our modeling prediction.

Material Characterization for Reliable Resin Transfer Molding Process Simulation

Resin transfer molding (RTM) technologies are widely used in automotive, marine, and aerospace applications. The need to evaluate the impact of design and production critical choices, also in terms of final costs, leads to the wider use of numerical simulation in the preliminary phase of component development. The main issue for accurate RTM analysis is the reliable characterization of the involved materials. The aim of this paper is to present a validated methodology for material characterization to be implemented and introduce data elaboration in the ESI PAM-RTM software. Experimental campaigns for reinforcement permeabilities and resin viscosity measurement are presented and discussed. Finally, the obtained data are implemented in the software and then compared to experimental results in order to validate the described methodology.

Experimental Study of Thickness Gradient and Flow Simulation in VARTM Process

Vacuum assisted resin transfer moulding (VARTM) process is widely used for manufacturing composite products. It is very difficult to manufacture a composite component with small dimension tolerance using VARTM process. In this research paper, carbon fiber reinforced polymer (CFRP) flat plates have been manufactured using the VARTM process with a different combination of process parameters. The carbon fiber laminates with different thickness have been manufactured using the VARTM process. The thickness of manufactured components has been measured at different locations using non-contact type 3D scanning techniques. The warpage has been determined for each manufactured components. The compaction pressure has been measured using pressure gauge at a different location during manufacturing. The thickness variation, pressure variation and volume fraction have been determined across the length for each manufactured components for different thickness laminates. The mould filling time has been calculated using the numerical approach in ANSYS Fluent software and the same has been compared with experimental results. The percentage difference between the experimental and numerical approach has been found within 5 %.

Effects of 3-aminophenylacetylene on mechanical properties at elevated temperatures of carbon fiber/phthalonitrile composites

Abstract High temperature mechanical properties are crucial for successful application of carbon fiber (CF) reinforced composites in aerospace engineering field etc. Here CF reinforced composites based on our own developed phthalonitrile blend (APN10) modified by 3-aminophenylacetylene (APA) were prepared by Resin Transfer Molding (RTM) process. The effects of 3-aminophenylacetylene (APA) addition were studied on the composite mechanical properties at elevated temperatures. The results show that the processability of CF/phthalonitrile composites is greatly improved by the addition of APA. The RTM processing window as wide as 3 h at 150 °C is achieved when 10 wt% APA is added to the phthalonitrile resin blend. Meanwhile, the 5% weight loss temperature (Td5) of the as-prepared composites is higher than 550 °C and the glass transition temperature (Tg) of the composites is higher than 530 °C, exhibiting excellent thermal stability. In particular, the addition of APA can significantly enhance the mechanical properties at high temperatures of the CF/phthalonitrile composites. The retentions of flexural strength, flexural modulus and interlaminar shear strength at elevated temperatures (400 °C and 500 °C) of the as-prepared CF composites with proper contents of APA are relatively higher than those of the previously reported heat-resistant composites based on phthalonitrile resins. The roles of the short molecule length and catalysis of APA at high temperatures are analysed in the high mechanical retentions at elevated temperatures of the CF/phthalonitrile composites.

Optimization method to reduce three‐dimensional thermal gradients in resin transfer molding

ABSTRACTPresently, the mold and resin are heated to promote resin flow and shorten curing period in order to improve manufacturing efficiency of resin transfer molding (RTM). This nonisothermal manufacturing process easily generates three‐dimensional thermal gradients in the direction of resin flow and thickness of composite part. However, the existing heating systems only consider the thermal gradients along thickness direction. The thermal gradients in direction of resin flow cannot be reduced which will lead to residual stress even deformation and cracking in composite part. This article aims at reducing the three‐dimensional thermal gradients in the direction of resin flow and thickness of composite part. Based on the theory of energy and fluid flow, an optimization method of heating system design by using numerical simulation is proposed. The results show this method reduces the three‐dimensional thermal gradients effectively in composite part manufactured by RTM process. This study can provide powerful tools for heating system design to manufacture composites products in polymer industry. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48948.

Hybrid Effect in In-Plane Loading of Carbon/Glass Fibre Based Inter- and Intraply Hybrid Composites

Experimental studies are presented on quasi-static tensile and compressive loading of composites hybridised at two levels: intraply and interply. Consistent reinforcements in the form of novel unidirectional fabrics were developed using T700SC carbon and E-CR glass fibres. Composites were manufactured using Resin Transfer Moulding process with epoxy resin and characterised to ensure consistency and comparability, further enabling easier understanding and confirmation of hybrid effect in a reliable way. Failure strain in tension for interply hybrid revealed a positive hybrid effect of +7.4%, while interply hybrid showed a negative hybrid effect of −6.4% in compression. Intraply hybrid with three carbon and three glass tows blocked together demonstrated the best mechanical performance among all hybrids; synergistic effects of +17.8% and +39.6% in tensile and compressive strength, respectively, was observed for this hybrid configuration. The results show that different hybridisation strategies can be exploited to balance cost and performance of composites for structural and lightweight applications.

Fabrication and tensile behavior of post-consumer carpet waste structural composite

India is most populated country and stands on second position after China and most of the people utilized carpet regularly. Carpet is generally utilized by every household and mostly used in institutions, decorations, parties, etc. for flooring purpose. Carpet remains in good condition for maximum one or two years after which they deteriorate and becomes waste. This huge quantity of post-consumer carpet waste is thrown into landfill sites creating severe health problems, air pollution etc. In order to reduce the rise of this landfill sites we need adopt major some steps towards recycling of such waste, and thus save environment from waste deposition. Therefore in this study an effort has been done to fabricate low strength structural composite by Vacuum Assisted Resin Transfer Molding (VARTM) process. The tensile behavior of prepared composite has been determined by computerized universal testing machine (UTM). The composite has been fabricated in two different ways by joining either the two fiber surfaces or two back surfaces together with the help of epoxy. The results shows that composite fabricated by joining the two fibers surfaces has higher strength and the obtained results also indicate that the fabricated composites can be conveniently used as structural composites for light weight application.

Experimental and numerical investigation of compressive mechanical behaviour on woven carbon-Kevlar hybrid composites

Advanced polymer textile composites are characterised with high strength to weight ratio and tailored mechanical properties claiming their applications in advanced engineering sectors. The research work presented is focused on the development and characterisation of compressive behaviour of monolithic Kevlar and carbon-Kevlar hybrid fabric reinforced polymer composites (FRPCs). Vacuum-assisted resin transfer moulding process is used to cast the composite laminates. Results obtained present the effect of hybridisation of carbon yarns with Kevlar fabric, also compare the compression modulus and compressive strength of two fabrics along longitudinal axes. Fabrics with different weaving patterns, namely plain and twill are considered for reinforcement to experimentally investigate the role of weaving pattern plays in governing the mechanical strength of textile composite. FE model is generated to numerically simulate the compression loading behaviour of composites. Simulation results of longitudinal compression of carbon-Kevlar hybrid fabric composite show a good agreement with experimental results.