Vacuum Assisted Resin Transfer Molding Method Research Articles

Significant enhancement of mechanical properties for glass fiber fabric‐reinforced polyamide 6 composites by improving interfacial bonding

AbstractIn fiber‐reinforced composites, the interfacial bonding between fibers and the matrix is crucial for determining the material's performance. A vacuum‐assisted resin transfer molding (VARTM) process was utilized in this work to fabricate glass fiber fabric‐reinforced polyamide 6 (GFF/PA6) composites through in‐situ polymerization using caprolactam (CL) as the precursor. To enhance the fiber‐matrix interfacial bonding, polyethylene glycol (PEG) was incorporated into the polymerization system, improving the hydrogen bonding between the matrix and fibers. Morphological observations and interface layer analysis revealed that the introduction of PEG resulted in improved interfacial bonding and increased interface layer thickness. Molecular dynamics simulations indicated that the amino formate groups formed by the reaction with PEG exhibited more hydrogen bonds with the hydroxyl groups on the glass fiber surface, thereby promoting interfacial bonding between the matrix and fibers. When the PEG content was 10 wt%, the tensile strength and the elongation at break of the corresponding composite increased by 160% and 300% compared to GFF/PA6 composites without PEG. This study presents a promising strategy for enhancing the fiber‐matrix interfacial bonding by modifying the matrix, offering a prospective approach for developing high‐strength thermoplastic composites.Highlights GFF/PA6 composites were fabricated via the VARTM method. The addition of PEG for matrix modification improved the interfacial bonding. The modification enhances the hydrogen bonding between the matrix and fibers. Good interfacial bonding can greatly promote the crystallization of the matrix. The composites exhibited a significant increase in strength and toughness.

The effects of glass fiber sheet lamination on the connection strength of single-bolted pultruded glass fiber reinforced polymer profiles

In this study, a series of experiments and finite element analyses were conducted to investigate the effects of glass fiber sheet (GFS) lamination on the strength of pin-bearing single-bolted pultruded glass-fiber-reinforced polymer (PGFRP) connections. In the experiments, nine types of GFS lamination were molded using the vacuum-assisted resin transfer molding method (VaRTM) and bonded onto the surfaces of PGFRP members. Then, four different end distances of PGFRP plates to bolt diameters ( e/ d) were surveyed, ranging from 3 to 6. The results indicated that all types of GFS lamination offered excellent improvement effects for the ultimate loads of the PGFRP connections. The strengthening effects were better when the connections had smaller e/ d values. In addition, external 0°/90° GFSs provided the best performance for GFS-strengthened PGFRP connections with medium e/ d values. Finally, it was demonstrated that finite element analysis (FEA) could be a useful method for predicting the failure loads of GFS-strengthened PGFRP connections.

Uji Kekuatan Bending Pipa Komposit Jute-Epoxy pada Perlakuan Rendaman Air Panas

The main purpose of this study was to determine the comparison of the bending strength of composite pipes when treated with hot water. In this study, composite pipes were made using woven sacks and tied with an epoxy matrix which was molded using the VARTM (Vacuum Assisted Resin Transfer Molding) method. Jute fiber laminated composite on epoxy binder is made by laminated 3 layers with fiber direction 450 and has a thickness of 2.55 mm, the jute-epoxy composite pipe will be treated with heat treatment. Then tested on bending loading. The results of this study were the bending stress and strain on the control specimen compared to the heat treated specimen, an increase in the strain of the heat treatment specimen was 0.007 [MPa], this was due to the heat treatment temperature on the specimen which caused a change in the properties of the specimen itself, which was initially a brittle specimen changes to plastic. Meanwhile, the value of bending stress and modulus of elasticity on control specimens and heat treatment specimens. The obtained stress on the control composite pipe is 67.946 [MPa] with a modulus of elasticity of 10.398 [GPa]. While the heat-treated composite pipe has a bending stress of 28.613 [MPa] with an elastic modulus of 2.225 [GPa].

Different Curing Temperature Effects on Mechanical Properties of Jute/Glass Fiber Reinforced Hybrid Composites

In this study, the effect of different curing temperatures (60°C,80°C, and 100°C) on the mechanical characteristics of Jute and Glass fiber-based hybrid composites were analyzed mechanically, physically, and morphologically. Jute fiber fabric and glass fiber fabrics (49 gr/m² and 100 gr/m²) were used as reinforcement elements, while epoxy was utilized as ma-trix materials. A vacuum assisted resin transfer molding method (VARTM) was used as the production method. The mechanical test results were achieved by the Tensile test and Vick-ers hardness test, while morphologic images were obtained by Scanning Electron Microsco-py (SEM). Physical data was also obtained by the ignition loss test. The effects of tempera-ture and hybridization on mechanical properties of hybrid composite samples formed with jute fabric and glass fiber material with different weights per square meter at different cur-ing temperatures are given in the results. Results show that increasing post cure temperature 60°C to 80°C 3.18%-3.41% rate augment in tensile strength. It was discovered that there was a decreasement in tensile strength with an increase in temperature from 80 °C to 100 °C after curing. In the hardness test results, increasing post curing temperature had an increas-ing effect on the hardness values. SEM analysis results also supported the tensile test re-sults.

Production and Characterization of Carbon-Kevlar-Aramid Reinforced Layer Composites with VARTM Method

In this study, laminated composite materials are produced by Vacuum Assisted Resin Transfer Molding (VARTM) Method. Three different reinforcement materials (carbon, kevlar and aramid) are used in the production phase. Tensile test is applied to the samples after the production and in the light of SEM images, fractured surfaces of the samples and their results are evaluated. It is obvious that the mechanical properties of carbon fiber reinforced samples yield better results.

The energy-absorbing characteristics of carbon fiber-reinforced epoxy honeycomb structures

This paper investigates the compression properties and energy-absorbing characteristics of a carbon fiber-reinforced honeycomb structure manufactured using the vacuum-assisted resin transfer molding method (VARTM). The composite core materials were manufactured using a machined steel baseplate onto which hexagonal blocks were secured. A unidirectional carbon fiber fabric was inserted into the slots and the resulting mold was vacuum bagged and infused with a two-part epoxy resin. After curing, the hexagonal blocks were removed, leaving a well-defined composite honeycomb structure. Samples were then cut from the composite cores and inspected in an X-ray computed tomography machine prior to testing. Mechanical tests on the honeycomb structures yielded compression strengths of up to 35 MPa and specific energy absorption values in excess of 47 kJ/kg. When normalized by the density of the core, the resulting values of specific strength were significantly higher than those measured on traditional core materials. The unidirectional cores failed as a result of longitudinal splitting through the thickness of the core, whereas the multidirectional honeycombs failed in a combined splitting/fiber fracture mode, absorbing significantly more energy than their unidirectional counterparts. Increasing the weight fraction of fibers served to increase the strength and energy-absorbing capacity of the core. Finally, it was also shown that introducing a chamfer acted to reduce the initial peak force and precipitate a more stable mode of failure.

EFFECT OF ORIENTATION ANGLES ON VIBRATION PROPERTIES AT CARBON FIBER REINFORCED POLYMERIC COMPOSITES

In this study, composite plates with dimensions of 300x300mm were produced by VARTM (Vacuum Assisted Resin Transfer Molding) method using unidirectional carbon fiber fabrics. The composite plates were produced symmetrically at four different orientations ((0°) 4 ,(60°/-30°) S ,(45°/-45°) S , (0°/90°) S ) and four layered. Required specimens according to three-point bending and vibration tests related ASTM standards for were cut from produced plates. The maximum flexural stresses of the specimens were determined by performing three-point bending tests. Free vibration tests under fixed-free boundary conditions were performed to determine their natural frequencies and damping ratios. As a result of the tests, specimens with (0°) 4 directional angles were found to have the highest bending strength. Also, composite specimens with orientation angles (0°) 4 have the highest natural frequencies and lowest damping ratios. (45°, -45°) S , the natural frequency values were the lowest while the damping ratio values were found to be the highest.

An experimental study on low-velocity impact response of nanocomposite beams reinforced with nanoclay

The low-velocity impact (LVI) response of the unidirectional glass/epoxy laminated composites, which were reinforced with various contents of nanoclay (i.e., 0, 3, 5 and 7 wt %) was performed using a drop-weight impact machine. The nanocomposite beams were fabricated using two different methods, including hand lay-up (HLU) and vacuum assisted resin transfer molding (VARTM) methods, to evaluate the effect of the manufacturing method on the impact response. In addition, the influence of the nanoclay type on the impact response was assessed by using Cloisite 30B and Cloisite 15A. The quasi-static and LVI responses of the nanocomposite beams were compared, and the effect of nanoclay on the delaminated area after impact was also discussed. The comparative results of the experiments indicate that the samples fabricated via VARTM method, have a smaller damage area and more energy absorption than the HLU types. However, the beams with 5 wt % nanoclay have the highest energy absorption in both manufacturing methods. Moreover, the mechanism of smaller delaminated area with increasing nanoclay contents is explained according to the impermeable nature of nanoclays.

Effect of microwave irradiation on carbon fiber/epoxy resin composite fabricated by vacuum assisted resin transfer molding

The effects of microwave irradiation for resin-curing of carbon fiber/epoxy resin composite (CFRTS), which was fabricated by vacuum-assisted resin transfer molding (VARTM) method, were investigated at 2.45 GHz frequency. The mechanical properties of CFRTS cured by microwave irradiation for 20 min at 120 °C were similar as compared to the conventional oven for 300 min at 120 °C. Moreover, the CFRTS irradiated by microwave had better adherence property between fiber and resin as compared to conventional oven at same resin-curing time. From the relation between resin-curing and mechanical property, it was found that the curing rate of microwave-irradiated CFRTS was 15 times faster as compared to conventional heating. Furthermore, the activation energies for resin-curing reaction on conventional- and microwave-cured CFRTS were estimated to be 2.7 and 1.3 × 104 J/mol, respectively. The resin-curing reaction in CFRTS prepared by VARTM method was significantly promoted by microwave irradiation at short time.

Electrical and thermal conductivities of carbon fiber composites with high concentrations of carbon nanotubes

High concentrations (1.1–3.7 wt%) of carbon nanotubes (CNTs) were incorporated into carbon fiber (CF)-reinforced epoxy composites by different fabrication methods. A mat-like form of CNT (CNT mat) was inserted between plies of CF plain-weave fabric and the composite was processed by vacuum-assisted resin transfer molding (VARTM). Two similar CNT structures, CNT mat and buckypaper, were inserted between CF woven prepreg laminates and the corresponding CF prepreg composites were fabricated by curing either in an autoclave or in a hot press. For the final method, CNTs were directly grown onto CF plain weave fabric and hierarchical composites were fabricated from those CNT-CF fabrics by the VARTM method. Out-of-plane electrical and thermal conductivities were evaluated for the fabricated composites. Electrical conductivity was enhanced most for the hierarchical composites; thermal conductivity, for the CF fabric composites with CNT mat. The results are discussed in conjunction with optical microscopy images of the composites’ cross-sections.

Effect of surface treatments on the mechanical properties of natural fiber textile composites made by VaRTM method

In this study, we aimed to improve the strength of textile composites by applying surface treatments on natural fibers. Natural fibers used were flax and hemp, and the matrix was an epoxy acrylate resin. The flax fiber textile was treated with acetone, laundry detergent, and aqueous solution of sodium hydroxide, because water repellent substances were adhered to the fibers. Hemp fiber textile was chemically-treated with polysilazane, silane coupling agent, and coated by polyvinyl alcohol (PVA). These treatments were carried out to improve the adhesion by treating the fiber surface. Natural fiber textile composites were made by a vacuum assisted resin transfer molding (VaRTM) method. After molding, the effect of washing process and surface treatments was verified by tensile tests. The most effective washing process was alkali-treatment with an aqueous solution of sodium hydroxide. The alkali-treated flax fiber composite had its tensile strength improved by 19.7% compared to the untreated fiber composite. However, the tensile strength and Young’s modulus of surface treated hemp fiber composite were reduced. The effect of PVA coating was examined by using a micro-droplet method. The interfacial shear strength of PVA-coated hemp fiber was reduced compared to that of untreated hemp fiber. In addition, the interfacial shear strength was reduced with increasing PVA content.

Thickness and Fiber Content Optimization in VARTM Method for High Speed Craft

To improve production efficiency and quality of fiber-glass boatyards many research have been done both through technological as well as management aspects. One of these developments is Vacuum Assisted Resin Transfer Molding (VARTM) which is claimed to have high strength and material efficiency. This method has not much been applied in Indonesian boatyards, most of them are still using conventional hand lay-up. The research is aimed to investigate the strength of the composite and the optimum amount of materials to obtain the required strength for its application on boat buildings. Experimental approach was conducted in the research using 800 biaxial and 900 unidirectional E-glass for reinforcement, and vinylester (RIPOXY R-802-EX-1) resin for the matrix. The ultimate tensile strength and Youngs modulus of the composites are obtained through tensile and flexural test based on ASTM D 3039 and ASTM D 790 standards. The data obtained are used to determine the optimum number of layers and fiber content on certain locations of the boat hull structure in order to comply with the requirements of classification rules.

Thickness and Fiber Content Optimization in VARTM Method for High Speed Craft

To improve production efficiency and quality of fiber-glass boatyards many research have been done both through technological as well as management aspects. One of these developments is Vacuum Assisted Resin Transfer Molding (VARTM) which is claimed to have high strength and material efficiency. This method has not much been applied in Indonesian boatyards, most of them are still using conventional hand lay-up. The research is aimed to investigate the strength of the composite and the optimum amount of materials to obtain the required strength for its application on boat buildings. Experimental approach was conducted in the research using 800 biaxial and 900 unidirectional E-glass for reinforcement, and vinylester (RIPOXY R-802-EX-1) resin for the matrix. The ultimate tensile strength and Youngs modulus of the composites are obtained through tensile and flexural test based on ASTM D 3039 and ASTM D 790 standards. The data obtained are used to determine the optimum number of layers and fiber content on certain locations of the boat hull structure in order to comply with the requirements of classification rules.

탄소나노튜브로 보강된 탄소섬유복합재의 제조공정과 층간전단강도

Carbon nanotubes (CNTs) have been widely investigated as reinforcements of CNT/polymer nanocomposites to enhance mechanical and electrical properties of polymer matrices since their discovery in the early 90`s. Furthermore, the number of studies about incorporating CNTs into carbon fiber reinforced plastics (CFRP) to reinforce their polymer matrices is increasing recently. In this study, single-walled carbon nanotubes (SWNT) were dispersed in epoxy with 0.2 wt.% and 0.5 wt.%. Then, the SWNT/epoxy mixtures were processed to carbon fiber composites by a vacuum assisted resin transfer molding (VARTM) and a wet lay up method. The processed composite samples were tested for the interlaminar shear strength (ILSS). The relationship between the interlaminar shear strengths and processing, and the reinforcement mechanism of carbon nanotubes were investigated. CNT/epoxy nanocomposite specimens showed the increased tensile properties. However, the ILSS of carbon fiber composites was not enhanced by reinforcing the matrix with CNTs because of processing issues caused by increased viscosity of the matrix due to addition of CNTs particularly for a VARTM method.

Effect of Local Off-Axis Fibers Array on Tensile Properties of CFRP Laminae

CFRP (Carbon fiber reinforced plastics) exhibit superior mechanical properties, and are recently applied to large structural materials using the VaRTM (Vacuum assisted Resin Transfer Molding) method. In the vicinity of the resin inlet of this method, and at the joint of CFRP structures, it is pointed out that the disorder in fiber orientation often occurs. In this study, therefore, the effect of local off-axis fibers array on the tensile properties of unidirectional CFRP was basically investigated. An experimental device for making a local off-axis fibers array on a CFRP lamina was newly developed, and various unidirectional CFRP laminae were prepared by changing the fiber orientation angle and the size. The results show that the tensile strength of CFRP laminae with off-axis fibers array decreases with increasing the fiber orientation angle and the length, and depends on the degree of fiber bundle waving. On the other hand, Young's moduli of the CFRP lamnae show an almost constant value, which is relatively close to that of CFRP lamina without off-axis fibers array. Finally, Young's moduli and tensile strength of the CFRP laminae were analyzed from a proposed composite model with an off-axis fibers array, and its validity was discussed.