Vacuum Assisted Resin Infusion Molding Research Articles

Investigations on the influence of thickness and preform structure on the mechanical performance of novel textile composites with woven Kevlar® fabric reinforcement and poly methylmethacrylate (Elium®) matrix

Abstract Elium (novel methyl methacrylate (MMA)) resin is a liquid thermoplastic resin curable at room temperature and a possible replacement for epoxies. The main objective of this work is to evaluate the mechanical characteristics of novel Kevlar fabric reinforced Elium composites with different thicknesses. The plain-woven structure Kevlar/Elium laminates were manufactured with 1.5 mm and 2.5 mm thicknesses through vacuum-assisted resin infusion moulding, where 8 and 12 layers of woven fabrics were used, respectively. The effect of laminate thickness was measured in terms of mechanical (tensile, flexural, shear, and dynamic mechanical analysis (DMA)) and physical (density and fibre volume fraction (FVF)) characteristics. The density of the laminates was found in the range of 1.18–1.31 g cm−3. FVF was 50.69 and 52.27% for 1.5 and 2.5 mm thick laminates, respectively. The composite with 1.5 mm thickness exhibited the highest tensile strength (667.9 MPa) and flexural strength of 330.7 MPa. Conversely, the highest interlaminar shear strength measured for 2.5 mm thick laminate is 16.5 MPa. The DMA analysis recorded the highest storage and loss modulus for 2.5 mm thickness laminates. The fractography analysis confirmed the quantified experimental observation of excessive interface debonding and delamination. Elium composites may be suitable for high-end structural applications, including marine and aircraft structures.

Reprocessable carbon fiber vitrimer composites: Reclamation and reformatting of carbon fibers for second generation composite materials

AbstractCarbon fibers (CFs) are experiencing a growing demand owing to their low specific weight, exceptional mechanical properties, superior temperature, and corrosion resistance, however, their sustainability and energy consumption during manufacturing is still a challenge. Therefore, reclamation of waste CFs and their reformatting has gained significant attention. Herein, we synthesized a chemically degradable vitrimer matrix by curing bisphenol‐A diglycidyl ether (BADGE) with 2‐aminophenyl disulfide (2‐AFD) and further utilized the matrix for the development of CF reinforced composites (CFRCs) through vacuum‐assisted resin infusion molding (VARIM) process. The obtained vitrimeric system and its composites show excellent mechanical, self‐adhering, shape‐memory, and reprocessing properties. Meanwhile, the developed CFRP vitrimer composites can be rapidly dissolved in thiol solvent (1‐octanethiol), resulting in the efficient recycling of CFs. X‐ray diffraction, scanning electron microscopy, and Raman spectroscopy validate that the chemical structure of the recycled fibers closely resembles the structure of the original CFs. The recycled CFs were further used to prepare second generation composite materials with excellent thermal, dynamic, and mechanical properties for nonstructural applications (e.g., sports, automotive, etc.). Thus, with an effective CF recycling method, this study can assist in preparing reliable, long‐term functional, recyclable, and high‐performance composites.

Effect of MWCNTs on static, dynamic, and wear performance of Vacuum Assisted Resin Infusion Molding (VARIM) processed glass fabric/epoxy polymer composites

In the present work, MWCNTs were used in wt.% of 0.075, 0.15, and 0.3 in epoxy resin, and then glass fabric/epoxy polymer (GF/EP) composites were fabricated using VARIM setup. The mechanical and wear properties of GF/EP composites were compared with and without the addition of MWCNTs. Maximum improvement in tensile and flexural performance were seen in GF/EP composites at 0.15 weight percent MWCNT addition when compared to a neat GF/EP one, based on static testing such as tensile and flexural tests. High-cycle fatigue test results show a relatively higher cycle count with 0.15 wt.% MWCNTs addition in the GF/EP composite compared to the GF/EP without the addition of MWCNTs. The wear performance also improved with a lower friction coefficient as well as a lower track depth and width for MWCNTs with added GF/EP than plain GF/EP composite. Therefore, in addition to decreasing surface softening and improving the wear performance of glass fabric epoxy composites, MWCNTs (0.15 weight percent) increased the interfacial adhesion at the fiber/matrix interface. This study establishes an optimum ratio of 0.15 wt.% of MWCNTs addition in glass fabric/epoxy polymer composites for enhancement in their mechanical and wear performance.

EXPERIMENTAL ANALYSIS OF THE EFFECT OF THE WOVEN ARAMID FABRIC ON THE STRAIN TO FAILURE BEHAVIOR OF PLAIN WEAVED CARBON/ARAMID HYBRID LAMINATES

Remarkable advances in the research and development of micro/mini Unmanned Aerial Vehicles (UAVs) seek thin, lightweight and strong materials for their structural applications. As these structures involve various loading conditions in both the in-plane and through-the-thickness directions during their life cycle, the assurance of the structural stability in each direction is deemed mandatory. The woven Aramid fibers as high strain materials (HSM) are known to improve the through-the-thickness impact strength. However, the addition of the HSM can affect the overall tensile behavior of composite laminates. This study investigates the effect of the woven Aramid fiber on the in-plane tensile behavior of Carbon/ epoxy laminates. Laminates are fabricated using an easy and cost-effective Vacuum Assisted Resin Infusion Molding (VARIM) setup. A uniaxial tensile test was conducted to analyze the tensile behavior of Carbon/Aramid hybrid composites. The effect of adding the woven Aramid layer and the Carbon fabric sequence on the tensile modulus, strain to failure and modulus of toughness are investigated in this study. The results revealed that the presence of Aramid has a positive hybrid effect on the failure strain, exhibiting pseudo-ductile behavior with a compromise in the tensile modulus of the virgin Carbon/epoxy laminate.

Enhancing fracture toughness of carbon fiber/epoxy composites using polyphenylene ether as a modifier

AbstractIn this study, carbon fiber/epoxy composites (CFRP) were fabricated by vacuum‐assisted resin infusion molding (VARIM) with polyphenylene ether (PPE) as a toughening agent. The PPE contained hydroxyl end groups that facilitated chemical bonding with epoxy during curing. PPE was incorporated into the epoxy matrix by dissolution, and spreading in the interlaminar regions. The presence of PPE as a toughener exhibited significant improvement in the Mode‐I fracture toughness of the composites. The CFRP samples, which were toughened with 5 wt.% and 10 wt.% PPE, showed about 191% to 380% enhancement, respectively, in the critical energy release rate (GIC) compared to the unmodified sample. Dynamic mechanical analysis (DMA) showed about a 6°C increase in the glass transition temperature of the toughened composites, which is an interesting aspect of this work. These results indicate the potential of using PPE as a toughening agent in CFRP composites.

Compressive performance of full-scale GFRP composite sandwich wall panels with wood core

This paper investigated the compressive behaviors of sandwich wall panels consisting of glass fiber-reinforced polymer (GFRP) face sheets and Paulownia wood core experimentally and numerically. Vacuum-assisted resin infusion molding (VARIM) process was used to produce GFRP sandwich wall panel specimens. Four full-scale wall panels with different heights were tested under axial loading to study their failure modes and load-bearing capacities. The results revealed that buckling was the main failure mode of GFRP wall panels under the axial compression and the ultimate load-bearing capacities of specimens were improved the decrease of the height-to-thickness ratio. Experiments showed that decreasing the height-to-thickness ratio from 51.5 to 38.6 can effectively improve the ultimate load-bearing capacities of the wall panels by 124%. The experimental results were compared with finite element analysis (FEA) and analytical results were in good agreement. In addition, an equation was used to predict the load-bearing capacities of the wall panels suitable for the specimens with smaller height-to-thickness ratio.

Impact of Resin Flow Velocity on the Mechanical and Thermal Properties of Fiber-Reinforced Composites Fabricated via Vacuum Assisted Resin Infusion Molding (VARIM) Process

Impact of Resin Flow Velocity on the Mechanical and Thermal Properties of Fiber-Reinforced Composites Fabricated via Vacuum Assisted Resin Infusion Molding (VARIM) Process

A comparative study of static and fatigue performance of glass and basalt fiber reinforced epoxy composites

AbstractThis work compares the tensile and fatigue behavior of unidirectional glass fiber/epoxy (GFRPs) and basalt fiber/epoxy (BFRPs) composites manufactured using vacuum‐assisted resin infusion molding (VARIM). The tensile and fatigue tests are performed, and results show that both GFRPs and BFRPs have very similar tensile behavior, whereas BFRPs perform better than the GFRPs in terms of fatigue life and degradation of properties, showing about 75 MPa more fatigue limit. The S–N curve shows that BFRPs resist fatigue failure and stiffness degradation due to their better interfacial adhesion. Fractographic observations reveal fatigue failure mechanisms of both BFRPs and GFRPs. From the regression analysis performed, an S–N curve was fitted with a model available in the literature, and regression parameters were calculated. Dynamic mechanical analysis of both BFRPs and GFRPs was performed to evaluate parameters like glass transition temperature, storage modulus, and loss modulus. From the findings of this research, BFRPs may be recommended as a suitable alternative to GFRPs.Highlights This article compares the tension–tension fatigue properties of unidirectional GFRPs and BFRPs. From the research work, the authors found that BFRPs perform better than GFRPs under fatigue loading. The stiffness degradation behavior of GFRPs and BFRPs are studied and compared. Scanning electron micrographs of fractured samples are used to observe fatigue failure mechanisms. Dynamic mechanical analysis (DMA) was performed to determine the storage modulus, loss modulus, glass transition temperature, and damping coefficient (tanδ) for both composites.

Enhancing tensile performance and CFRP/steel interface properties of CFRP plates with nano-SiO2 and MWCNTs

The mechanical performance of carbon fiber reinforced polymer (CFRP) is a crucial parameter influencing the effectiveness of CFRP reinforcement. The addition of nano-toughening agents to the resin matrix can effectively enhance the mechanical properties of CFRP. This paper investigates the influence of nano-SiO2 and MWCNTs content (0.2, 0.4, and 0.6 wt%) as well as their blending ratios (1:3, 1:1, 3:1) on the tensile properties of CFRP plates using the vacuum assisted resin infusion molding (VARIM) process. Additionally, an assessment is conducted to evaluate how the tensile performance of CFRP plates affects the CFRP plate/steel interface performance.The results indicate that the resin viscosity increases with the addition of nano-toughening agents, with the resin viscosity experiencing a respective increase of 32.9% and 92.7% when incorporating 0.6 wt% nano-SiO2 or MWCNTs compared to pure resin. The inclusion of nano-toughening agents enhances the tensile strength of CFRP plates, with a more pronounced effect observed when adding 0.4 wt% nano-SiO2 or MWCNTs, resulting in respective increases of 41.5% and 31.5% compared to pure CFRP plates. When nano-SiO2 and MWCNTs are mixed, the tensile performance of the CFRP plate is inferior to that of plates with the same individual nano-toughening agents content. This is attributed to the excessively high viscosity of the resin matrix during mixing, hindering complete infiltration of carbon fibers. Therefore, in the manufacturing process of CFRP plates using the VARIM technique, it is advisable to consider resins with lower viscosity. Additionally, the utilization of CFRP plates with superior tensile performance contributes to enhanced CFRP/steel interface properties, although the tensile performance of CFRP plates does not alter the bonding slip curve of CFRP/steel double-lap joint specimens.

The effects of graphene oxide addition on low velocity impact performance of aramid fiber reinforced epoxy composites

AbstractIn this study, the impact of incorporating graphene oxide (GO) nanoparticles into the matrix of aramid fiber reinforced polymer (AFRP) composites was investigated. The GO nanoparticles were dispersed in the AFRP matrix at three different weight percentages: 0.1%, 0.3%, and 0.5%. The fabrication of the GO dispersed AFRP nanocomposites was achieved using the vacuum assisted resin infusion molding (VARIM) method, and the AFRP plates were cut using a water jet. The sectioned specimens of the fabricated nanocomposites were subjected to low velocity impact tests. The effects of introducing GO nanoparticles at different percentages were evaluated by analyzing the contact force, deflection, maximum absorbed energy versus time and contact force versus deflection curves. Finally, the key parameters of low velocity impact, including contact force, deflection, and maximum absorbed energy, were compared for the different fabricated AFRP nanocomposites. Based on the results, the AFRP composite with 0.3 wt.% of GO nanoparticles exhibited the best performance under low velocity impact loading conditions. However, the agglomeration of nanoparticles became a significant challenge when higher percentages of GO nanoparticles were added to the composite structure. The findings highlight the importance of determining the optimal percentage of nano materials for incorporation into composite structures.

Synergistic effect of compatibilized nanoclay/polyethylene fibers on the impact strength of epoxy‐glass fiber nanocomposites

AbstractEpoxy‐based glass fiber nanocomposites (EGFCs) have good static mechanical properties but lack in impact strength. Addition of thermoplastic fillers to EGFCs enhanced the impact strength but with lowered static properties. To overcome this issue, compatibilized polyethylene (PE) fibers and silanized clay platelets were reinforced in the EGFCs. The unique properties of PE fibers such as good toughness, high strength, resistance to chemicals, and light‐weight made them an ideal choice for this purpose. EGFCs were processed through vacuum‐assisted resin infusion molding (VARIM) technique and resulted in significant improvements in an impact strength. Compatibilization of nanoclay/PE fibers was confirmed using FTIR and SEM‐EDS analysis. Nanoclay morphology in EGFCs was determined using XRD and TEM analysis. Reinforcement of maleic anhydride grafted PE fibers and silanized nanoclay in EGFCs significantly increased the impact strength by160% over the reference EGFC (without nanoclay/PE fibers). FE‐SEM micrographs showed improved interfacial interaction among various constituents of EGFCs resulting in superior mechanical performance. The newly developed EGFCs have myriad applications in various industries, namely, automotive (bumpers, frames for racing bicycles etc.), marine (hulls, decks, etc.), aviation (radome, stabilizers, etc.), and sports (archery bows, vault poles, etc.).Highlights Multi‐scale filler‐reinforced EGFCs fabricated through VARIM process. Compatibilized reinforcement significantly improved impact strength. Silanization of nanoclay validated with FTIR & morphology with XRD/TEM technique. SEM‐EDS and FTIR confirmed successful compatibilization of PE fibers. SEM showed improved interfacial interaction among various constituents of EGFCs.

Low velocity impact behavior of twill basalt/epoxy composites modified by graphene nanoparticles

Nanoparticles are considered as feasible strengthening agent which strengthen different types of polymeric materials with minor reduction in the density of composites. In this study, 0.1 and 0.5 wt. % Graphene Nano Platelets (GNPs) are added to the matrix of basalt fiber reinforced epoxy composites (BECs) and the effects of such addition on low velocity impact behavior are investigated. In this regard, the epoxy matrix is reinforced in macro scale by basalt fibers weaved together in 2/2 Twill pattern. Vacuum Assisted Resin Infusion Molding (VARIM) method is used to fabricate the pure and multi-scale BECs. The profile energy method is also used to evaluate the penetration and perforation threshold of fabricated pure and multi-scale BEC specimens. The force versus time and deflection, energy and deflection versus time curves are plotted and the key parameters of low velocity impact test including maximum force, energy and deflection are compared. According to the results, introducing of GNP nanoparticles in the matrix of BECs improves the low velocity impact behavior of these composites by increasing the contact force and decreasing the absorbed energy in rebounding state. Finally, based on the experiments, the 0.5 wt.% BEC has the best impact performance by applying 15.08 kN impact force against the applied forces of 13.78 kN and 11.208 kN for 0.1 wt.% and pure BECs.

Analysis of Sandwich Composite Manufacture with Triaxial-Processed Foam Core by Vacuum-Assisted Resin Infusion Moulding and Resin Reinforcement

Analysis of Sandwich Composite Manufacture with Triaxial-Processed Foam Core by Vacuum-Assisted Resin Infusion Moulding and Resin Reinforcement

The influence of addition of carbon nanotube and graphene platelets on characteristics of carbon/basalt fiber reinforced intra‐ply hybrid composites

AbstractIn this study, effects of addition of carbon nanotubes (CNTs) and graphene platelets (GPLs) on characteristics of carbon/basalt fiber reinforced intra‐ply hybrid composites were investigated. The composites were fabricated using vacuum assisted resin infusion molding (VARIM) method in two types including bare and 0.1, 0.5 wt.% of GPL and CNT nanoparticles filled hybrid composites. Fabricated normal and multiscale composites were cut by water jet and mechanical properties of specimens were examined by tensile, flexural, SBS experiments. Therefore, the modulus of elasticity, flexural modulus, tensile and flexural strength and ILSS of bare and multiscale composites were compared. Thermomechanical properties of fabricated composites were evaluated by dynamic mechanic analyze (DMA), thermogravimetric analyze (TGA) and thermal conductivity (TC) tests and storage modulus, loss modulus, damping ratio, glass transition temperature, weight loss and derivative weight loss were compared in fabricated normal and multiscale composites. Similarly, modal properties of fabricated composites such as natural frequency and damping factor were obtained by vibrational tests and compared in fabricated composites. According to the results, the addition of carbon‐based nanoparticles improved the characteristics of carbon/basalt fiber intra‐ply hybrid composites. The response of composites was directly proportional to the addition ratio of the carbon‐based nanoparticles.

Low velocity impact response of sandwich composites with hybrid glass/natural fiber face-sheet and PET foam core

Abstract The focus of this study is manufacture of sandwich composites using palm and jute natural fibers with E-glass due to their high specific advantages such as lightweight, thermal insulation strength, biodegradability characteristics. The sandwich composites using in this study were fabricated using vacuum assisted resin infusion molding (VARIM) technique. The palm, jute and E-glass fibers were used as reinforcing materials, and PET foam core having a thickness of 10 mm was used as a core material. All specimens were then subjected to low velocity impact tests under various impact energy levels of 20 J, 30 J, 40 J, 50 J, and 60 J at room temperature. Force-time and force-deflection diagrams, maximum contact forces, contact times, and deflections corresponding to the peak forces, and absorbed energies of sandwich composites were obtained for each impact energy level in detail. Damages of sandwich composites are shown for selected energies. According to the obtained results, it was found out that the sandwich composite fabricated with palm fiber has a superior impact behavior in terms of maximum contact force compared to other configurations of sandwich composite (i.e., neat E-glass and jute reinforced E-glass).

An experimental study on the effects of introducing carbon nanotube on low velocity impact behavior of carbon/aramid fiber reinforced intra-ply hybrid composites

In this research, the addition effects of Multi Wall Carbon Nanotube (MWCNT) on low velocity impact behavior of Carbon/Aramid Fiber Reinforced (CAFRP) intra-ply hybrid composites were studied. In this regard, three types of pure, 0.1 wt.% and 0.5 wt.% introduced CAFRP intra-ply hybrid composites were fabricated by Vacuum Assisted Resin Infusion Molding (VARIM) method. The profile energy method was used to determine the penetration and perforation threshold. The main purpose of this research was to improve the impact behavior of CAFRP by addition of MWCNT to the matrix of these composites. The low velocity impact test was also carried out in 30, 50, 80 and 120 J energy values. The effect of addition MWCNTs in the matrix of composite was investigated by plotting force, absorbed energy and deflection vs. time and the key parameters of impact test such as maximum contact force, absorbed energy, deflection and duration time were compared for pure and multi scale CAFRP composited. According to the results, the addition of MWCNT improved the low velocity impact behavior of CAFRP intra-ply hybrid composites by not only increasing the toughness of epoxy matrix but also upgrade the adhesion of carbon fibers to the epoxy matrix. It was also found that fiber breakage, fiber pull out, matrix cracking, delamination and fiber matrix debonding were the most important failure modes in these types of tested composites.

Investigation of Dynamic Mechanical Behavior of Nanosilica Filled Carbon-Kevlar-Epoxy Polymer Hybrid Nanocomposite

Reinforcement of epoxy-carbon-Kevlar fabric composite with the addition of nanosilica has resulted in the evolution of new hybrid polymer nanocomposite, which results in the improved mechanical properties of polymer hybrid nanocomposite. The current investigation concentrated on the dynamic mechanical behavior of unfilled and nanosilica filled carbon-Kevlar-epoxy polymer composite with five and four layers of carbon and Kevlar woven fibers respectively with epoxy matrix (5C4K). Nanosilica was mixed into the epoxy at different weight percentages (wt.%) of 0, 0.5, 1.0, and 1.5. The laminates were fabricated using the vacuum-assisted resin infusion moulding (VARIM) technique. The dynamic mechanical properties, storage modulus, loss modulus, damping factor (tan delta), and glass transition temperature was investigated using a dynamic-mechanical analyzer at temperature ranging from 25 to 165 degrees Celsius. The test specimens were prepared in accordance with the ASTM D4065 standard to investigate dynamic mechanical analysis (DMA) of the hybrid polymer nanocomposite. The results of the tested specimens for dynamic mechanical behaviors of carbon-Kevlar-epoxy hybrid nanocomposites are very much influenced by the presence of nanosilica. The storage modulus, loss modulus for nanosilica added hybrid polymer composites were more than the unfilled ones and the damping factor (tan delta) was observed more in an unfilled composite.

Anisotropic behaviors of moisture absorption and hygroscopic swelling of unidirectional flax fiber reinforced composites

This work aims to study the anisotropic moisture absorption characteristics of unidirectional flax fiber reinforced composites (FFRCs) and evaluate the variations of the internal stress caused by the hygroscopic deformation, which might lead to the deterioration of the mechanical properties of the composites. FFRCs were prepared using vacuum-assisted resin infusion molding (VARIM) technology. Moisture absorption tests were designed by sealing the designated surfaces with a polyurethane waterproof coating to keep the moisture absorption of FFRCs only in the desired directions. The deformation caused by moisture absorption in the width direction was also monitored. It confirms that the moisture absorption of FFRCs conformed to the 3D Fick's law, and the influence of moisture absorption in the width direction cannot be ignored, especially for the unidirectional transverse tensile test specimen (UTFRC). The hygroscopic deformation of the unidirectional FFRCs showed that the material expands perpendicular to the fiber direction but shrinks along the fiber direction. The modified 3D Fick’s law based on heat conduction equation was performed to reveal the mechanism of the above moisture absorption and hygroscopic deformation. According to the finite element inversion, it was found that the axial diffusion coefficient along flax fiber bundles was much larger than the transverse diffusion coefficient perpendicular to the fiber bundle direction due to the existence of the unique lumen structure inside flax fibers. In addition, the high internal stress caused by the mismatched swelling properties between the fiber and the matrix was the main reason for the damage of the FFRCs, especially at the interface, which may seriously affect the service life of the composites. The outcome of this study can be used to accurately analyze the hydro-elastic behaviors of plant fiber reinforced composites, which is a prerequisite for predicting the mechanical properties affected by moisture absorption.

Experimental investigation of the impact behavior of glass/epoxy composite materials with the natural fiber layer

Abstract Owing to their specific advantages like thermal insulation, being lightweight and strong, laminated composites were designed by using natural fiber (female or male palm fiber) between two layers of glass stitched [0°/90°] to improve the impact properties of glass/epoxy composite. Natural fiber is cheap and plentiful in Iraq. The composite material was manufactured by vacuum assisted resin infusion molding (VARIM) at 80 °C for a duration of 8 h. The low velocity impact response of laminated composite was investigated experimentally. Impact tests were conducted on the composite specimens by Ceast Fractovis Plus impact test machine with constant mass of 5.03 kg at room temperature for the impact energies of 20 J, 30 J and 40 J. After impact tests, maximum contact forces versus impact energy, contact force versus deflection and absorbed energy-impact energy curves are drawn. The obtained results showed that the addition of palm fibers to glass/epoxy composite materials made significant contributions in absorbing energy and delaying the damage mode.

Three-Dimensional Permeability of Thick-Section Glass Fabric Reinforced Polymer Composite by Vacuum-Assisted Resin Infusion Molding

Abstract Determination of permeability of thick-section glass fabric preforms with fabric layers of different architectures is critical for manufacturing large, thick composite structures with complex geometry, such as wind turbine blades. The thick-section reinforcement permeability is inherently three-dimensional and needs to be obtained for accurate composite processing modeling and analysis. Numerical simulation of the liquid stage of vacuum-assisted resin infusion molding (VARIM) is important to advance the composite manufacturing process and reduce processing-induced defects. In this research, the 3D permeability of thick-section E-glass fabric reinforcement preforms is determined, and the results are validated by a comparison between flow front progressions from experiments and from numerical simulations using ansys fluent software. The orientation of the principal permeability axes were unknown prior to experiments. The approach used in this research differs from those in literature in that the through-thickness permeability is determined as a function of flow front positions along the principal axes and the in-plane permeabilities and is not dependent on the inlet radius. The approach was tested on reinforcements with fabric architectures which vary through-the-thickness direction, such as those in a spar cap of a wind turbine blade. The computational simulations of the flow-front progression through-the-thickness were consistent with experimental observations.