Resin Transfer Molding Research Articles

Demonstration of temperature monitoring of the curing process in resin transfer moulding using integrated phase-shifted Bragg grating sensors

Composite materials have increased in use across multiple industries due to their low weight, thermal stability and design flexibility. As applications grow, the importance of accurate process-monitoring techniques grows, with various research teams investigating a variety of in situ cure-monitoring sensors. Photonic integrated circuits (PICs) can be a feasible solution in tracking curing cycles due to their resistance to harsh conditions and ease of integration into the production tool. This paper demonstrates the integration and performance evaluation of an embedded phase-shifted Bragg grating solution, instead of commonly used fiber sensors, based on 220 nm height silicon-on-insulator platform for in-situ monitoring of the RTM-6 resin curing process in a composite tool. The embedded optical sensor presents high sensitivity (75 pm/°C) and linearity (R2=0.995) up to 120 °C, enabling precise temperature measurements throughout the curing cycle. The experimental results show consistency with previously reported simulations, throughout the calibration, dry run characterization and the curing process, up to 120 °C, allowing for accurate monitoring of the curing process.

Effect of hygrothermal aging on mechanical properties of continuous flax fiber composites

AbstractThe influence of hygrothermal aging on the mechanical properties of flax fiber‐reinforced polymer (FFRP) composites was studied by examining the mechanical properties and failure mechanism of the composite laminates exposed in distilled water at different temperatures. The resin transfer molding (RTM) process was used to manufacture FFRP laminates, which were then subjected to accelerated aging tests in distilled water at different temperatures. The moisture absorption characteristics of FFRP were analyzed by a water absorption test. Tensile, bending, and low‐velocity impact tests of laminates after different aging conditions were performed. Combined with DSC and FTIR tests, the failure mechanism of FFRP exposure to hygrothermal aging was analyzed. The result indicated that the increase in temperature will accelerate the moisture absorption process of FFRP, and the hygroscopic behaviors at different temperatures conform to Fick's law. In the early stage of hygrothermal aging, the composites undergo post‐curing, and the tensile and bending strengths increase. After that, the tensile and bending strengths are decreased because of the thermo‐oxygen aging of materials and fiber/matrix interface damage. After hygrothermal aging, the impact peak force of FFRP decreases obviously while the absorbed energy increases due to the increase of internal defects and plasticization of composites. The increase of hygrothermal aging temperature aggravates the aging of materials, resulting in a more obvious decline in the tensile, bending, and impact properties of the composites.Highlights The effect of hygrothermal aging on the mechanical properties of FFRP is investigated. With the increase of hygrothermal aging time, the tensile and bending strength of FFRP increased at the early stage of aging and then decreased. After hygrothermal aging, the impact peak force of FFRP decreases and the absorbed energy increases due to the increase of internal defects and plasticization of composites.

Application of machine learning for composite moulding process modelling

Fibre-reinforced composites are commonly manufactured through moulding processes such as Resin Transfer Moulding (RTM) due to their great reliability and scalability. State-of-the-art RTM process modelling and simulation primarily rely on computationally expensive physics-based modelling methods. Given the great volume of possible input-output combinations, process optimisation via exhaustive physics-based simulations or experiments becomes unfeasible. Hence, this paper proposes the integration of machine learning to facilitate composite moulding process modelling. The well-established PixelRNN, an image-based machine learning model, is employed to model and simulate the complex composite mould filling phenomenon. Upon training and validation, the developed PixelRNN metamodels demonstrated impressive prediction accuracies of up to 97.35 % at 50 % training data proportions, at roughly half the cost of exhaustive simulations. The results of this early study convincingly underscore the promising potential of machine learning in composite moulding applications, particularly when utilising graphical input data rather than the traditional numeric data.

Three‐dimensional graphene architecture reinforced epoxy composite with double‐sided adhesive molybdenum disulfide transition interlayer for maintaining excellent interfacial and tribological properties

AbstractThree‐dimensional graphene architecture (3DGA) as reinforcement with successive reinforcement effect has attracted intense attention in the field of polymer composites, while 3DGA also faces the disadvantages of weak interfacial adhesion with matrices. The surface decoration of 3DGA with molybdenum disulfide (3DGA@MoS2) further promoted the diffusion and penetration of epoxy molecular for 3DGA network with the aid of resin transfer molding (RTM) technic. The MoS2 transition nanolayer not only forms covalent bonding with 3DGA but mechanical interlocks with epoxy, which effectively improved the interface combination in composite. Compared with neat epoxy, the glass transition temperature (Tg) and tensile strength increased by 18°C and 58.6%, as well as the average friction coefficient and wear rate decreased by 84% and 89%, respectively, by low loading of only 2 wt% 3DGA@MoS2. Hence, the 3D graphene modified strategy by surface decoration provides a new insight for manufacturing high‐performance epoxy‐graphene composites with excellent tribological properties.Highlights A highly ordered and interconnected 3DGA reinforcement was fabricated. MoS2 serves as interlayer, forming covalent bond and mechanical interlock. Incorporation of 3DGA@MoS2 enables rapid heat conduction and load transfer. Bi‐interpenetrating 3D structure/polymer network endows good wear resistance. Improved comprehensive properties ascribe to strong interface adhesion.

Low-flammability carbon fiber reinforced composites based on low-viscosity phosphorus-containing epoxy binders for transfer molding methods

This study is the first investigation into the possibility of low viscosity phosphorus-containing epoxy binders using triglycidyl phosphate for carbon fiber-reinforced polymers (CFRPs) production by resin transfer molding (RTM). Rheological studies and flammability evaluations were carried out to determine the optimum concentrations of triglycidyl phosphate in the epoxy binder. The introduction of triglycidyl phosphate into the epoxy composition was shown to produce self-extinguishing epoxy polymers. In addition, the curing kinetics of the phosphorus-containing epoxy binder was evaluated using differential scanning calorimetry (DSC) to optimize the curing process. The impregnation process of the product in the PAM-RTM software package was modeled to evaluate the possibility of obtaining large-size CFRP parts based on the developed binder by transfer molding methods. The physical-mechanical and fire-resistant tests of CFRPs showed significant improvement in flame-retardant properties in the modified samples, while maintaining high values of strength and elastic modulus. The study concluded that the introduced triglycidyl phosphate significantly affects the binder properties by reducing the viscosity, and increasing the flame retardancy, thus opening a promising direction for developing advanced composite materials.

Epoxy Vitrimer Formulation for Resin Transfer Molding: Reactivity, Process, and Material Characterization

Epoxy Vitrimer Formulation for Resin Transfer Molding: Reactivity, Process, and Material Characterization

Effect of Chemical Treatments on the Mechanical Properties of Jute/Polyester Composites.

Natural fiber composites have been extensively studied for structural applications, with recent exploration into their potential for various uses. This study investigates the impact of chemical treatments on the properties of Brazilian jute woven fabric/polyester resin composites. Sodium hydroxide, hydrogen peroxide, and peracetic acid were utilized to treat the jute fabrics, followed by resin transfer molding (RTM) to form the composites. Evaluation included water absorption, flexural strength, tensile strength, and short-beam strength. The alkaline treatment induced changes in the chemical composition of the fibers' surface. Chemical treatments resulted in increased flexural and short-beam strength of the composites, with no significant alterations in tensile properties. The hydrogen peroxide treatment exhibited lower water absorption, suggesting its potential as a viable option for enhancing the performance of these composites.

An Enhanced Vacuum-Assisted Resin Transfer Molding Process and Its Pressure Effect on Resin Infusion Behavior and Composite Material Performance.

In this paper, an enhanced VARTM process is proposed and its pressure effect on resin infusion behavior and composite material performance is studied to reveal the control mechanism of the fiber volume fraction and void content. The molding is vacuumized during the resin injection stage while it is pressurized during the mold filling and curing stages via a VARTM pressure control system designed in this paper. Theoretical calculations and simulation methods are used to reveal the resin's in-plane, transverse, and three-dimensional flow patterns in multi-layer media. For typical thin-walled components, the infiltration behavior of resin in isotropic porous media is studied, elucidating the control mechanisms of fiber volume fraction and void content. The experiments demonstrate that the enhanced VARTM process significantly improves mold filling efficiency and composite's performance. Compared to the regular VARTM process, the panel thickness is reduced by 4% from 1.7 mm, the average tensile strength is increased by 7.3% to 760 MPa, the average flexural strength remains at approximately 720 MPa, porosity is decreased from 1.5% to below 1%, and the fiber volume fraction is increased from 55% to 62%.

Influence of MoS2 nano-filler additions on wear behavior of carbon fiber reinforced epoxy composites

In this research work, two body wear and three-body wear performance of carbon fabric reinforced HTR 212 epoxy resin(CF/Epoxy) composites are experimentally evaluated. Carbon fabric/epoxy resin composite panels with MoS2 nano-filler additions of 0.1, 0.2, 0.4 and 0.7 weight percentage are developed by Vacuum Assisted Resin Transfer Molding process. Two Body Wear test is conducted on the prepared specimen in accordance with ASTM G-99, whereas Three Body Abrasive wear test is conducted as per ASTM G-65. Experimental Tests are conducted for sliding and abrading distances in multiples of 250 m up to 1500 m. Results reveal that Carbon fabric/epoxy resin composites with 0.7 weight percent of MoS2 show 18% reduction in two body wear compared to a decrease of 35% in Three Body abrasive wear at 1500 m abrading distance. Scanning Electron Microscopy is used to study the surface morphology of the tested samples and to know the mode of damage at the surface.

Near-infrared spectroscopy in resin transfer molding—determination of the degree of cure

Near-infrared (NIR) spectroscopy is employed to directly monitor the degree of cure of composite material during the curing phase in the resin transfer molding (RTM) process. The composite material consists of natural fibers and an epoxy-amine resin system. The quantitative determination of the degree of cure, α, from the NIR spectra is realized by partial least square (PLS) regression in conjunction with various pre-treatments of the spectral data. As a reference, the degree of cure is determined by isothermal differential scanning calorimetry (DSC) experiments. The best PLS model that could be obtained for α is characterized by a determination coefficient of prediction (R²P) of 0.980 and root mean square error of prediction (RMSEP) of 4.4 %. While the spectra change during curing according to the literature for each RTM trial, significant differences can be observed between the spectra of different RTM trials. The reasons for this are discussed in detail. The findings show the potential of inline NIR spectroscopy for monitoring α in the RTM process.

Dynamic wetting performance and resin-flow behavior of two-level selective laser-etched metal surface in resin transfer moulding process of fiber-metal laminates

ABSTRACT In selective laser etching for the interfacial strengthening of Fiber Metal Laminates (FMLs), the wettability of customized structured features significantly affects their overall mechanical properties. For two-level features, their complicated geometry makes the evaluation of wettability difficult, which introduces challenges to feature design. In this study, a sandwich FMLs comprising an AA2024-O metal skin and a plain-woven carbon-fiber fabric core is investigated. Three types of two-level feature interfaces are designed and introduced into the FMLs structure. To understand the effect of two-level features on the resin flow and dynamic wetting progress in resin transfer molding, two-phase flow Computational Fluid Dynamics numerical models coupled with porous media and level-set numerical methods are built. The feasibility of the numerical simulation in the qualitative analysis was verified by comparing the results with those of the testing porosity values from X-ray scanning. In addition, the mechanisms of pore formation and transportation are revealed. These results indicate that the deeper groove structure in the etched features plays an important role in discharging residual air and determining the transformation of pores to reduce porosity. The permeability orientations of the porous media and surface structure both have significant impacts on the flow behavior and formation of pores.

A Novel Preparation Method of Composite Bolted T-Joint with High Bending Performance Based on the Prepreg-RTM Co-Curing Process.

A co-curing resin system consisting of 9368 epoxy resin for prepreg and 6808 epoxy resin for resin transfer molding (RTM) was developed. A corresponding preparation method for a novel polymer composite bolted T-joint with internal skeleton and external skin was proposed based on the prepreg-RTM co-curing process, and novel T-joints were fabricated. A series of conventional configuration T-joints based on the RTM process and T-joints made of 2A12 aluminum alloy were prepared simultaneously. Bending performances were studied on these T-joints experimentally. The results indicate that 9368 epoxy resin and 6808 epoxy resin exhibit good compatibility in rheological and thermophysical properties. The novel T-joints prepared with the prepreg-RTM co-curing process show no obvious fiber local winding or resin-rich regions inside, and the interface quality between the internal skeleton and the external skin is excellent. The main failure modes of the novel T-joint under bending load include the separation of the skin and skeleton and the fracture along the thickness on the base panel; the skeleton carries the main bending load, but there is still load transfer between external skin and internal skeleton through their interface. The internal damages of the novel T-joint are highly consistent with surface damages observed visually, facilitating the detection and timely discovery of damages. The initial stiffness, damage initiation load, and ultimate load of the novel T-joint are 1.65 times, 5.89 times, and 3.45 times that of the conventional T-joint, respectively. When considering the influence of the density, the relative initial stiffness and relative ultimate load of the novel T-joint are 1.44 times and 2.07 times that of the aluminum alloy T-joint, respectively.

Development of lightweight and high-strength glass fiber and natural fiber hybrid composites using VARTM technique

This research paper presents the synthesis of Glass Fiber Reinforced Plastic (GFRP) and Natural Fiber Hybrid Composites (NFHC) utilizing Vacuum-Assisted Resin Transfer Molding (VARTM) techniques. Jute and flax fibers were strategically selected for their unique properties and potential synergistic effects when combined with glass fibers. The study systematically evaluates the influence of natural fiber incorporation on the mechanical performance of the composites, focusing on critical factors such as fiber type, orientation, and resin selection. A series of meticulously crafted laminate configurations were employed. These included combinations of glass and jute fibers (GJG, GJGJG), glass and flax fibers (GFG, GFGFG), and a reference laminate composed solely of glass fibers (GGGGG). The mechanical characterization involved rigorous Izod impact testing, hardness assessments, and water absorption tests to provide a detailed understanding of behavior of composite material. The results reveal that the incorporation of jute fibers resulted in a significant enhancement of impact resistance of up to 59 % compared to GFG laminates and hardness. Water absorption varied across the laminates, with GGGGG exhibiting the lowest value of 0.054 %. Scanning Electron Microscopy (SEM) was employed to gain valuable insights into the critical fiber-matrix interaction and microstructure of the composites, further elucidating the observed mechanical properties. These findings pave the way for lightweight, high-strength composites ideal for engineering applications, particularly automotive mono leaf springs. The resulting weight reduction promises significant gains in fuel efficiency and vehicle performance, advancing sustainable materials with exceptional mechanics.

Simultaneous port number and location optimization of mold gates‐vents using in‐house coded stochastic multi‐objective optimization algorithm

AbstractThis research introduces multi‐objective stochastic optimization (MOSO) and non‐dominated sorting differential evolution (NSDE) in‐house coded algorithms for enhancing the optimization of the resin transfer molding (RTM) process during the mold‐fill phase for composite parts. Glass fiber‐vinyl ester‐based automotive bonnet and carbon fiber‐RTM6‐based aircraft wing flap parts were used as the case studies. Initially, the NSDE algorithm was developed for the simultaneous optimization of dry‐spot content and mold‐fill time by changing the locations of gates and vents with pre‐fixed port numbers. Then, the MOSO algorithm was designed for the concurrent optimization of the dry‐spot content, mold‐fill time and total number of ports by changing both the numbers and locations of gates and vents. The effect of race‐tracking was also investigated using higher permeability values at the composite part‐cut edges. When compared, the MOSO algorithm predicted less dry‐spot content, number of ports, mold‐fill time and uniform resin flow‐front progressions with lesser functional evaluations and computational time than the NSDE algorithm.Highlights The non‐dominated sorting differential evolution (NSDE) and multi‐objective stochastic optimization (MOSO) algorithms were developed for the optimization of the mold fill phase of resin transfer molded composite parts. The development of the NSDE algorithm aimed to concurrently optimize the dry‐spot content and mold‐fill time by changing the locations of gates and vents with pre‐fixed port numbers. The MOSO algorithm was designed to concurrently optimize dry‐spot content, mold‐fill time, and the total number of ports by varying both the numbers and locations of gates and vents. The MOSO algorithm predicted better‐automated mold‐fill phase optimalities for the resin transfer molded composite parts compared to the NSDE algorithm.

Chemo‐rheological and quantitative dispersion analysis of mass‐produced graphene‐unsaturated polyester based nanocomposites

AbstractRecent advancements in mass production of graphene powders utilize less energy‐intensive methods and milder chemicals compared to traditional lab‐scale techniques. This can influence the properties of the resulting graphene particles. This study investigates the effect of mass‐produced graphene powder on the curing and rheological properties of a resin transfer molding (RTM) grade unsaturated polyester resin. An objective dispersion quantification method was established to track the dispersion state of the nanocomposite throughout the curing process. The findings reveal that the graphene powder accelerated the curing evidenced by a shift in the peak temperature and gel point towards lower values. The sample containing 1 wt.% graphene exhibited remarkable dispersion stability with only 7.1% decrease by gelation. The resin matrix's low viscosity enhanced graphene particles mobility, while its fast‐curing nature allowed less time for agglomeration.Highlights Characterization of unsaturated polyester nanocomposites modified with an industrial‐grade graphene powder Real‐time in‐situ monitoring of graphene's dispersion state Quantification dispersion analysis for an objective dispersion assessment

Comprehensive Composite Mould Filling Pattern Dataset for Process Modelling and Prediction

The Resin Transfer Moulding process receives great attention from both academia and industry, owing to its superior manufacturing rate and product quality. Particularly, the progression of its mould filling stage is crucial to ensure a complete reinforcement saturation. Contemporary process simulation methods focus primarily on physics-based approaches to model the complex resin permeation phenomenon, which are computationally expensive to solve. Thus, the application of machine learning and data-driven modelling approaches is of great interest to minimise the cost of process simulation. In this study, a comprehensive dataset consisting of mould filling patterns of the Resin Transfer Moulding process at different injection locations for a composite dashboard panel case study is presented. The problem description and significance of the dataset are outlined. The distribution of this comprehensive dataset aims to lower the barriers to entry for researching machine learning approaches in composite moulding applications, while concurrently providing a standardised baseline for evaluating newly developed algorithms and models in future research works.

Environmental Impact of an Innovative Aeronautic Carbon Composite Manufactured via Heated Vacuum-Assisted Resin Transfer Molding

The Vacuum-Assisted Resin Transfer Molding (VARTM) process has gained popularity as a reliable and cost-effective alternative to autoclave molding for high-performance composite production, which is especially interesting for aeronautics, where weight reduction is crucial. However, to date, the environmental impact of components produced through VARTM remains relatively unknown. To address this gap, this study applied the Life Cycle Assessment (LCA) methodology to estimate the environmental impact of a thermoset composite laminate produced through heated VARTM. Aiming to support the decision, the VARTM composite part’s production was compared to conventional autoclave manufacturing, and the influence of alternative end-of-life (EoL) scenarios and energy mixes was considered, through LCA. The study found that energy consumption represented the majority of the environmental impacts of the heated VARTM component (33%), followed by carbon fibers, resins, consumables, and wastes. In terms of the comparative analysis, the autoclave manufacturing process showed better environmental results. Regarding EoL management, supercritical hydrolysis (with heat recovery) recycling emerges as the most beneficial method, reducing the impacts of the VARTM-manufactured component by 25%. This study emphasizes the importance of sustainable practices, such as reducing energy consumption, using low-carbon energy mixes, and adopting recycling methods to improve VARTM composite’s environmental performance.

Analyzing the Tensile Strength of Carbon Fiber-Reinforced Epoxy Composites Using LabVIEW Virtual Instrument

Carbon fiber-reinforced polymer composites are widely used materials in the aircraft industry, automotive sector, marine applications, civil engineering, and daily consumer goods, due to their superior mechanical properties at a relatively low density compared to metallic materials. The studied composites are composed of an epoxy resin matrix in which three layers of carbon fiber fabric are embedded, oriented at 0 and 90 degrees. Carbon fiber-reinforced polymer composites were manufactured using the Vacuum Assisted Resin Transfer Molding technique. The tensile failure mechanism in carbon fiber-reinforced polymer composites is an extremely complex phenomenon influenced by numerous factors. This study aims to evaluate the mechanical behavior of carbon fiber-reinforced composites through tensile testing and to compare experimentally obtained results with those calculated using the mixture rule. Additionally, the behavior of the materials under tensile stress was analyzed using the digital image correlation method. Estimating mechanical properties based on the mixture rule is a common practice in the design phase of polymer composites. This study s novelty and originality lie in its anticipation of the tensile strength and modulus of elasticity of the studied composites. This anticipation was achieved using a virtual instrument developed in the LabVIEW graphical programming environment. The experimentally obtained results for the tensile characteristics of the studied materials are suitable for this type of composite. These results were compared with estimates derived from the mixture rule, and the absolute error was determined.

Vibration Response of Thermoplastic Veil Interleaved Carbon Fiber Reinforced Epoxy Composites

Plate composite structures are used in many sectors today. Therefore, the demand for these structures is increasing. Especially in the field of aerospace, layered composite structures attract more attention. These wide range of applications affect composite materials in various aspects such as dynamic and mechanical in terms of working environments. Time-dependent variable stresses, vibrations and fatigue that occur in structures subjected to dynamic loads adversely affect both the internal and external structure of composite materials. This situation reduces the safe service life of composite materials. It is an important problem to eliminate or minimize the parameters that negatively affect the economic service life of fiber reinforced layered composite structures. In order to overcome these problems, it is aimed to create new composite structures by adding two different thermoplastic veil layers between fiber fabrics, which are widely used on an industrial basis. In this study, carbon fiber was used as the fiber fabric and Polyamide (PA) and Polyether ether ketone (PEEK) veils were used as the thermoplastic veil layers. The productions were made by Vacuum Assisted Resin Transfer Molding (VARTM) method and dynamic (natural frequency and damping ratio) tests were performed according to the relevant ASTM standards. With the experimental results obtained, the dynamic properties of thermoplastic veil-layered carbon fiber/epoxy composites were comparatively investigated to determine the effect of both veil layers and different fiber contents.

Experimental investigation of conductive heat transfer and fire protection in a polymer-based plate heat exchanger

Polymer-based heat exchangers offer several attractive features for thermal management applications such as low-cost, lightweight, antifouling, and anti-corrosion characteristics. However, their thermal performance is compromised primarily by the low thermal conductivity and high-flammability. This work consists of developing new polymer-based plate heat exchangers, which are made from epoxy resin reinforced by banana fibres and manufactured using the vacuum bag resin transfer moulding technique. The aim of this research is to improve both the heat transfer efficiency and thermal protection. The proposed approach involves incorporating silicon carbide powder as charge into samples to increase their thermal conductivity, and applying an intumescent fire-retardant coating to improve their capacity to withstand heat and flames. To determine the efficacy of this approach, a cone calorimetry test was performed to examine the thermal distribution within the plate heat exchanger samples and to assess fire reaction parameters during a fire scenario. The results revealed a notable increase in thermal conductivity, due to the addition of silicon carbide powder. Furthermore, the intumescent fire-retardant coating substantially improved the samples’ thermal resistance. This result has been verified by thermogravimetric analysis conducted during this work. These findings suggest that using banana fibres-reinforced epoxy resin, combined with silicon carbide powder and intumescent fire-retardant coating, has the potential to enhance the overall thermal performances of plate heat exchangers. The addition of silicon carbide powder increases the thermal conductivity by 36%. This demonstrates the feasibility of utilizing sustainable and biodegradable materials to manufacture heat exchangers that are more efficient and eco-friendly.