Vacuum Assisted Resin Infusion Technique Research Articles

MODIFICATION OF WOVEN DENDROCALAMUS ASPER IN COMPOSITE APPLICATIONS

The aim of this study is to examine the influence of immersing Petung Bamboo in a NaOH solution on the tensile strength (TS) of composites containing an epoxy matrix. Petung Bamboo Webbing was given 0%, 3%, 6% and 9%, soaking treatment. The Composite utilised in this investigation was fabricated by the Vacuum Assisted Resin Infusion technique. Tensile testing of composites is conducted according to the ASTM D638-1 standard. The findings indicated a positive correlation between the concentration of NaOH immersion and the adhesion between the woven surface of Petung Bamboo and the matrix. Consequently, the TS of the Composite was enhanced. However, increasing the concentrations beyond a certain point leads to more degradation of the lignin and cellulose in the fibers, resulting in a loss in the strength of the composite. The Petung Bamboo woven reinforced Composite achieved the highest TS of 136.06 MPa after being treated with a 6% NaOH immersion. This was followed by a 3% NaOH immersion treatment resulting in a TS of 106.04 MPa. Without any NaOH immersion treatment, the composite had a TS of 97.31 MPa. The lowest TS of the composite was observed after a 9% NaOH immersion treatment, measuring 90.79 MPa. The Petung Bamboo wicker-reinforced composite with NaOH immersion treatment showed higher fiber pullout and fiber-matrix debonding failures, while higher NaOH treatment concentration reduced these failures.

Physical-Mechanical evaluation of a hybrid sisal fibre/banana stem fibre/bio epoxy biocomposite as a replacement alternative to conventional materials

This work develops a hybrid composite material using a bio-epoxy resin matrix reinforced with natural sisal and banana stem fibres. The vacuum-assisted resin infusion technique uses to define the appropriate proportions to guarantee the adhesion of the reinforcement. With the physical-mechanical characterisation of the density of 1041 Kg/mᶟ, a flexural resistance of 160.43 MPa, and Young's modulus of 2.17 GPa, the adhesion evaluated using SEM images (scanning electron microscopy) and shows separation between resin and reinforcement less than 10μm. With these properties, using the Granta Edu Pack tool, conventional materials such as polypropylene(PP), polyester, cellulose acetate, polystyrene (PS), Acrylonitrile Butadiene Styrene (ABS), cardboard and wood were found, with similar properties, and the hybrid biocomposite can replace that.

Fast Dynamic Siloxane Exchange Mechanism for Reshapable Vitrimer Composites.

To develop siloxane-containing vitrimers with fast dynamic characteristics, different mechanistic pathways have been investigated using a range of catalysts. In particular, one siloxane exchange pathway has been found to show a fast dynamic behavior in a useful temperature range (180-220 °C) for its application in vitrimers. The mechanism is found to involve 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) as an organic catalyst in the presence of hydroxyl groups. Using this new mechanistic approach, vitrimers with ultrafast stress-relaxation characteristics (relaxation times below 10 s) have been prepared with a readily available epoxy resin and siloxane-amine hardener. Subsequently, the low viscosity siloxane-containing vitrimer resin enabled the preparation of glass fiber-reinforced vitrimer composites using an industrially relevant vacuum-assisted resin infusion technique. The resulting composite was successfully thermoformed into a new shape, which makes it possible to envision a second life for such highly engineered materials.

Fabrication of aluminum honeycomb cored carbon fabric/epoxy composite sandwich structures via vacuum assisted resin infusion technique

AbstractA detailed step‐by‐step fabrication procedural document of thin‐walled aluminum honeycomb sandwich composite structures, panels, and specimens using vacuum assisted resin infusion process was delivered in this paper. By and large, honeycomb sandwich structures are made by keeping the honeycomb core in between two face sheets, which are glued with the help of adhesives. In the present fabrication process, aluminum honeycomb core was glued in between the carbon fabric reinforced epoxy composite face sheets through vacuum assisted resin infusion technique. The present paper is aimed at fabricating two configurations of honeycomb sandwich composite panels namely, without considering any filler material inside the honeycomb cell, with considering the filler material inside the honeycomb cell. Plastic pellets made up of poly carbonate were considered as filler material for stiffening the aluminum honeycomb sandwich composite panels.

Design, Development, and Characterization of Advanced Textile Structural Hollow Composites.

The research is focused on the design and development of woven textile-based structural hollow composites. E-Glass and high tenacity polyester multifilament yarns were used to produce various woven constructions. Yarn produced from cotton shoddy (fibers extracted from waste textiles) was used to develop hybrid preforms. In this study, unidirectional (UD), two-dimensional (2D), and three-dimensional (3D) fabric preforms were designed and developed. Further, 3D woven spacer fabric preforms with single-layer woven cross-links having four different geometrical shapes were produced. The performance of the woven cross-linked spacer structure was compared with the sandwich structure connected with the core pile yarns (SPY). Furthermore, three different types of cotton shoddy yarn-based fabric structures were developed. The first is unidirectional (UD), the second is 2D all-waste cotton fabric, and the third is a 2D hybrid fabric with waste cotton yarn in the warp and glass multifilament yarn in the weft. The UD, 2D, and 3D woven fabric-reinforced composites were produced using the vacuum-assisted resin infusion technique. The spacer woven structures were converted to composites by inserting wooden blocks with an appropriate size and wrapped with a Teflon sheet into the hollow space before resin application. A vacuum-assisted resin infusion technique was used to produce spacer woven composites. While changing the reinforcement from chopped fibers to 3D fabric, its modulus and ductility increase substantially. It was established that the number of crossover points in the weave structures offered excellent association with the impact energy absorption and formability behavior, which are important for many applications including automobiles, wind energy, marine and aerospace. Mechanical characterization of honeycomb composites with different cell sizes, opening angles and wall lengths revealed that the specific compression energy is higher for regular honeycomb structures with smaller cell sizes and a higher number of layers, keeping constant thickness.

Improvement of mechanical and thermal properties of hybrid composites through addition of halloysite nanoclay for light weight structural applications

In this work the effect of stacking sequence of Carbon (C)/Glass (G) fibers and halloysites addition (1, 3 and 5 wt.%) on the mechanical and thermal properties of the hybrid composites were explored. The composite laminates were prepared by using Vacuum Assisted Resin Infusion Technique (VARIT). The outcomes disclosed that the hybrid composites having sequence of C2G3C2 (2-Carbon/3-Glass/2-Carbon layers) showed better overall properties. Moreover, the addition of halloysites enhanced the mechanical and thermal properties of the C2G3C2 hybrid composites. In particular, the hybrid composites added with 3 wt.% of halloysites showed higher overall properties among the other hybrid composites investigated. Finally, the morphological analysis was performed on the fractured surface of mechanical tested composites to study the failure mechanisms occurred. Based on the obtained results it can be concluded that the C2G3C2 hybrid composites added with 3 wt.% of halloysite could be a suitable alternative light weight material for automobile, aerospace and building structures.

Numerical and experimental investigation on mechanical responses of plain woven CFRP composite under various loading cases

This paper studies the complex mechanical behaviour of woven carbon fiber reinforced polymer composites fabricated by Vacuum Assisted Resin Infusion technique. A strategy for modelling of woven composite using a continuum damage mechanic model is proposed in this research. Then different loading cases, including off-angle tension, punch and axial crushing of corrugated plate, were simulated and the numerical results correlate very well with experiments in terms of mechanical responses, which verifies the validity of the modelling strategy. However, it is found that simulation is greatly affected by some parameters including both material properties and model-specific parameters, such as potential fracture angle in the transverse direction, crush front softening parameter, contact penetration curve and thickness of crush trigger. All these parameters are determined and investigated in detail. Results show that impact responses of woven composites, including both in-plane and out-of-plane direction, can be predicted with enough accuracy.

Mechanical response of adhesively bonded composite joints subjected to vibration load and axial impact

In the present work, the effects of vibration and impact on the mechanical performance of adhesively bonded joint of fiber-reinforced plastic (FRP) composite structures were investigated experimentally, and the main failure modes were discussed. For this purpose, eight layered fiberglass composite plates were produced using vacuum assisted resin infusion technique. DP-460 adhesive was used for the joining of composite plates. In order to study the joint performance, the tensile test was carried out on adhesively bonded specimens subjected to vibration and impact. The changing parameters for this investigation are the number of vibration cycles and level of axial impact energy. Experimental results indicate that the vibration and impact have a great effect on joint strength. However, this effect is not always negative in contrary to the expected behavior. Certain values of impact load and vibration cycles applied to the joint improve the tensile strength of the adhesively bonded joint. This result shows a complex interaction between the composite plate and adhesive through the dynamic loading. This work provided a new approach to increase the mechanical properties of adhesively bonded joints applying the dynamic loads.

Experimental investigation of mechanical and machining parameters of hybrid nanoclay glass fiber-reinforced polyester composites

In this work, the effect of nanoclay addition to glass fiber-reinforced polyester composites is studied. The pristine glass fiber-reinforced polyester composites (i.e., staking sequence, kind of fabric used, etc.) and hybrid nanoclay in varying weight fraction (0, 1, 2, 3, 4 and 5 wt%) and glass fiber-reinforced polyester composite is prepared by vacuum-assisted resin infusion technique. Fracture toughness studies are done to analyze the critical stress intensity factor and critical strain energy release rate. The optimum mechanical properties are obtained for hybrid nanoclay glass fiber-reinforced polyester composites with clay content of 3 wt%. This paper also deals with the study of optimizing the cutting parameters (Cutting speed and feed rate) to obtain maximum mechanical properties in hybrid nanoclay glass fiber-reinforced polyester composites during drilling process. It has been found that the torque is unaffected with increase in cutting speed. On contrast with increase in feed and nanoclay weight fraction, the torque increases. The drilled samples are further subjected to mechanical testing. Tensile studies confirms that better mechanical properties are obtained for optimum machining parameter of (0.045 mm/rev, 210 rpm) for 3 wt% nanoclay and glass fiber-reinforced polyester nanocomposites. The hybrid clay and glass fiber-reinforced nanocomposites generally posses better mechanical properties compared with pristine glass fiber-reinforced polyester composites.

Investigation into Mode II interlaminar fracture toughness characteristics of flax/basalt reinforced vinyl ester hybrid composites

In this work, the influence of water absorption of flax and flax/basalt hybrid laminates is presented with the aim to investigating the Mode II interlaminar fracture toughness. Four types of composite laminates namely, neat vinyl ester (neat VE), flax fibre reinforced vinyl ester (FVE), flax fibre hybridised basalt unstitched (FBVEu) and flax hybridised basalt stitched (FBVEs), were fabricated by vacuum assisted resin infusion technique. Three-point-end-notched flexure (3ENF) tests were performed to evaluate the critical Mode II strain energy release rate (GIIC) and the crack length (R-curve) at dry and wet conditions, by using two data reduction methods. The morphology of delamination and the fracture shear failure of composite laminates were evaluated using scanning electron microscopy (SEM) and X-ray micro computed tomography (μCT). The results obtained that the fracture energy of FBVEu composites, GIIC init. and GIIC prop. were increased by 58% and 21%, respectively compared to that of FVE dry specimens. Moisture absorption phenomenon caused increasing in the ductility of matrix that improved the resistance to crack initiation. However, this was inverted to a reduction in the fibre/matrix interfacial strength of FBVEu wet composites and a deterioration in the delamination resistance to crack propagation. The critical strain energy release rate of neat VE increased from 157.84 J/m2 to 239.85 J/m2 with reinforcement of flax fibre composites. The experimental results confirmed that basalt fibre hybridisation enhanced the durability and water repellence behaviour of natural fibre reinforced composites.

Role of Nanofillers on Mechanical and Dry sliding Wear Behavior of Basalt- Epoxy Nanocomposites

Basalt fiber reinforced polymer composites are nowadays creating attention in both industrial and academic world. New developments are still under way to explore the application of these composites by tailoring their properties. The objectives of this research article is to evaluate the effect of the incorporation of Nano titanium dioxide (TiO2) alone and in combination with nano clay on the mechanical and tribological wear behaviour of Basalt fabric– Epoxy (BE) composites. A vacuum-assisted resin infusion technique (VARI) was employed to obtain a series of BE composites. The mechanical properties, including tensile strength, tensile modulus, elongation at break, and surface hardness, were investigated in accordance with ASTM standards. From the experimental investigation, it was found that the tensile strength and dimensional stability of the B–E composite increased with increasing fillers. The effect of different loads (10 to 30 N) and sliding distances from 2000 to 8000 m on the performance of the wear resistance of the composites were measured. Slight increase in coefficient of friction for nano Clay-BE composite, reduction of coefficient of friction was noticed for the nano TiO2 and TiO2/Clay filler filled composites. The wear loss of the composites decreased with addition of fillers and increased with increasing sliding distance. Failure mechanisms of the worn surfaces of the filled and unfilled composites were examined with SEM.

Effect of Nano TiO<sub>2</sub>/Clay on the Erosive Wear Behavior of Basalt-Epoxy Hybrid Composites at Elevated Temperatures

Materials added to the matrix help improving operating properties of a composite. In the last few years, nanofiller /polymer composite have been widely investigated because of their outstanding multifunctional properties. In order to improve the erosive wear resistance of composite, an attempt was made to use nanoTiO2 and nanoclay as filler for the basalt reinforced epoxy composite (BE). The impact velocity, filler concentration and temperature are the parameters used for the study. The composites were fabricated using vacuum assisted resin infusion technique (VARI) technique. The fabricated composite specimens were tested by using erosive wear test rig as per ASTM G76 under normal incidence. The result shows that the erosion rate increases with increase in temperature and impact velocity. However, nanoTiO2-filled BE composite exhibits lower erosion rate as compared to Nanoclay filled and unfilled composite. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM).

Synthesis, fabrication and mechanical characterization of reinforced epoxy and polypropylene composites for wind turbine blades

Failure of wind turbine blades usually originates from manufacturing defects or in-service defects. In this study, materials selection for manufacturing of wind turbine blades was carried out based on the mechanical and physical results obtained using the Cambridge Engineering Selector program. Thermoplastic and thermosetting composites were synthesized and processed using injection molding and vacuum assisted resin infusion techniques, respectively. Operating conditions (vacuum pressure and temperature) were optimized. The manufactured samples were tested and evaluated using destructive tests. Tensile and fatigue tests were carried out. Polypropylene random discontinuous glass fiber composites were synthesized and processed using mold injection technique. Epoxy-carbon, glass and carbon/Kevlar hybrid fiber composites were manufactured using vacuum assisted resin infusion technique. Surface morphology was characterized using scanning electron microscope analysis. Tensile strength and fatigue resistance were significantly improved by the presence of E-glass fiber (30 wt%) in polypropylene-glass fiber composites. The experimental results were compared with the Cambridge Engineering selector software database. Epoxy-carbon (carbon fiber fraction is 0.61) and carbon/Kevlar hybrid (fibers fraction is 0.6) composites showed superior mechanical properties. Epoxy/carbon composite can withstand stresses up to 1390 MPa at 106 cycles.

Flame retardant epoxy hybrid composite laminates prepared by vacuum-assisted resin infusion technique

Epoxy/glass fiber/organo-montmorillonite hybrid composites with triaryl phosphates and decabromodiphenyl oxide flame retardants were prepared by vacuum-assisted resin infusion technique. The effects of triaryl phosphates and decabromodiphenyl oxide on the flammability properties of epoxy/glass fiber/organo-montmorillonite composites were evaluated through UL-94 vertical flammability test and limiting oxygen index. Epoxy/glass fiber/organo-montmorillonite hybrid composite showed no rating in UL-94 test up to 40 phr of triaryl phosphates. Field emission scanning electron microscopy showed the amount of char formed increased, denser char structure and better coverage of glass fibers as triaryl phosphates loading increased. Interestingly, the hybridization of 30 phr decabromodiphenyl oxide with respect to 10 phr triaryl phosphates flame retardants showed V-0 rating with limiting oxygen index of 33%.

Damage behavior of potting materials in sandwich composites with pinned joints

Abstract The damage behavior of the potting materials around a pinhole, being used in the mechanical joints of sandwich composites, is investigated experimentally. The sandwich composite panels used in the tests were manufactured by the vacuum-assisted resin infusion technique. Each of the top and bottom face sheets of the panels consisted of two woven E-glass/epoxy layers. As the core material, PVC foam (AIREX® C70.55) was used. The potting material consists of an epoxy resin and hardener system mixed with short E-glass fibers (4 wt%). The diameter of the potting material D and the edge distance to the center of pinhole E were considered as the two main varied dimensions. They were chosen as D=10, 12, 15, and 18 mm and E=15, 20, and 25 mm. The damage mechanisms of the potting material and sandwich sections are presented by using load-displacement variations and images of the damaged samples, subjected to in-plane pin loading.

Advanced Composites with Multi-Functionality Enhanced by Nanoparticles

Continuous fibre (carbon or glass) composite laminates with an epoxy matrix modified by nanoparticles (nanosilica of 25 nm or nanocarbon of 35 nm) were fabricated using a vacuum assisted resin infusion technique, aided by hot pressing, that produces high performance composites of a fibre fraction over 60 vol%. The presence of nanoparticles enhances fibre-matrix adhesion, the transverse tensile strength, the unidirectional compression strength, and mode I interlaminar fracture toughness. In particular, the GF/EP composites with the conductive nanoparticles allow the in-situ monitoring of damage (e.g. delamination) growth and impact damage assessment using a novel method of electrical resistivity tomography.

Machinability Study of Hybrid Nanoclay-Glass Fibre Reinforced Polyester Composites

Glass fibre reinforced polyester composites (GRP) and hybrid nanoclay and glass fibre reinforced polyester nanocomposites (CGRP) are fabricated by vacuum assisted resin infusion technique. The optimum mechanical properties are obtained for CGRP with 3 wt.% nanoclay. Three types of drills (carbide twist drill D 5407060, HSS twist drill BS-328, and HSS end mill (4 flutes “N”-type end mill RH-helical flute)) of 6 mm diameters are used to drill holes on GRP and CGRP. Three different speeds (600, 852, and 1260 rpm) and two different feeds (0.045, 0.1 mm/rev) are selected as process parameters. The effect of process parameter on thrust force and delamination during drilling CGRP is analyzed for optimizing the machining parameters. The delamination factor is low for the optimum process parameter (feed = 0.1 mm/rev and speed 852 rpm). Microstructural analysis confirms that at higher feeds, delamination is low for CGRP drilled with carbide tools. In order to analyze the effect of nanoclay in CGRP on tool wear, 200 holes were drilled on CGRP samples with 3 wt.% nanoclay, and the tool wear is analyzed under optimized parametric condition. Tool wear is high in HSS twist drill compared with carbide drill. The presence of nanoclay also accelerates the tool wear.

Thermal behavior and flammability of epoxy/glass fiber composites containing clay and decabromodiphenyl oxide

Epoxy/glass fiber hybrid composites with organo-montmorillonite (OMMT) and decabromodiphenyl oxide (DBDPO) flame retardants were prepared by vacuum-assisted resin infusion technique. The effects of OMMT and DBDPO on the flammability properties of epoxy/glass fiber hybrid composites were evaluated through UL-94 vertical flammability test and limiting oxygen index (LOI). Thermal decomposition was studied by means of thermogravimetric analyzer (TG). Field emission scanning electron microscopy (FESEM) was used to study the char morphology of the epoxy hybrid composites after being subjected to UL-94 vertical flammability test. Epoxy/glass fiber/OMMT hybrid composites with DBDPO loading of 40 wt% showed V-1 rating, whereas an increase to 50 wt% loading showed V-0 rating. The LOI values increased from 22.7 to 39.9 % as the loading of DBDPO increased. The obtained TG results showed that the thermal stability of epoxy hybrid composites decreased as the DBDPO loading increased. DBDPO decomposed at a lower temperature to form bromine radicals, which reacted with the combustible gases to form hydrogen bromide to inhibit the flame spread in the gas phase. The condensed phase activity was shown in FESEM, in which a layer of compact and continuous char was formed in epoxy/glass fiber/OMMT/DBDPO hybrid composites.

Mechanical behaviors of glass/polyester composites after UV radiation

Composites were fabricated by using glass fabric as the reinforcement and polyester as the matrix with the vacuum assisted resin infusion technique. Specimens were radiated by a Model SJD-1 ultraviolet lamp with various durations. The bending behavior, tensile strength, and the elongation at break of the UV radiated and unradiated composite panels were tested. The deteriorated mechanical properties of treated specimens were noticed. Usually, the bending strength would gradually decrease with prolonged UV radiation. The same trend was also seen for the tensile intensity of the samples. The corrosion process of the polymer caused by the oxygen in the atom state would be accelerated by the presentation of the UV ray, resulting in a serious damage on the material.

Tensile and bending behaviours of laminates with various fabric orientations

Woven fabrics are probably by far the most commonly used forms of textile composites in structural applications, they generally consist of two sets of interlaced yarn components, known as the warp and weft yarns according to the yarn directions in the fabric. One of the major factors which influences the mechanical properties of the woven fabric composites is the stacking orientations of the fabric layers in the composites. Vacuum assisted resin infusion technique was employed to produce two-layer laminates with various fabric crossing angles. The bending and tensile behaviours of the specimens were measured, the results showed that both bending character and tensile strength were highly influenced by the orientation of the fabric layers in the laminates. Parallel lay-ups of the fabric would increase both the bending and tensile strength in a definite direction, meanwhile, elongation at break in that direction was also increased greatly. Distinctive fracture profiles were noticed when using different fabric orientations in the laminates.