Glass Fiber Reinforced Vinyl Ester Research Articles

Effects of vacuum infusion configuration on homogeneity of glass fiber reinforced polymer composites for automotive components

In this study, the effects of vacuum infusion configuration on the homogeneities of glass fiber reinforced vinyl ester composites have been evaluated. Three different sizes of samples (100x100, 500x500, and 1000x1000 mm) were fabricated. Three different configurations were used to fabricate the samples. The first two configurations had one inlet, while the third configuration had two inlets for resin infusion. Thickness variations and hardness (Shore D) measurements were performed to determine the homogeneities of the samples. The results revealed that, for small size samples, the configurations have no obvious effect on the homogeneity of the samples, both in terms of thickness variations and hardness values. However, for larger samples, the configuration where the resin is introduced into the preform in the center of the component showed better homogeneity than other configurations. Even a better distribution is assessed with the introduction of the resin in the center of the sample, although this configuration also resulted in thickness swellings in the central areas of the sample. The thickness swellings were observed around the inlet areas for all configurations. The study shows that the resin flow in the center of the component is preferable but thickness swelling must be considered when dimensional tolerances are critical.

Hydrothermal Ageing of Glass Fibre Reinforced Vinyl Ester Composites: A Review.

The use of glass fibre-reinforced polymer (GFRP) composites in load-carrying constructions has significantly increased over the last few decades. Such GFRP composite structures may undergo significant changes in performance as a consequence of long-term environmental exposure. Vinyl ester (VE) resins are a class of thermosetting polymers increasingly being used in such structural composites. This increasing use of VE-based GFRPs in such applications has led to an increasing need to better understand the consequences of long-term environmental exposure on their performance. The reliable validation of the environmental durability of new VE-based GFRPs can be a time- and resource-consuming process involving costly testing programs. Accelerated hydrothermal ageing is often used in these investigations. This paper reviews the relevant literature on the hydrothermal ageing of vinyl ester-based GFRP with special attention to the fundamental background of moisture-induced ageing of GFRP, the important role of voids, and the fibre-matrix interface, on composite mechanical performance.

An Effective Method of Modeling the Deformation Behavior of Polymer Sandwich Structures with Adhesive Joints

Polymer sandwich structures have high bending stiffness and strength and also low weight. Therefore, they are widely used in the transportation industry. In the conceptual design phase, it is essential to have a method to model the mechanical behavior of the sandwich and its adhesive joints accurately in full-vehicle scale to investigate different structure partitioning strategies. In this paper, a novel approach using finite element modeling is introduced. The sandwich panels are modeled with layered shells and the joint lines with general stiffness matrices. Stiffness parameters of the face-sheets and the core material are obtained via mechanical tests. Stiffness parameters of the joints are determined by using the method of Design of Experiments, where detailed sub-models of the joints serve as a reference. These models are validated with experimental tests of glass-fiber reinforced vinyl ester matrix composite sandwich structure with a foam core. By using two joint designs and three reference geometries, it is shown that the method is suitable to describe the deformation behavior in a full-vehicle scale with sufficient accuracy.

Enhanced creep resistance of GFRP composites through interpenetrating polymer network

Fiber reinforced polymer (FRP) composites have become promising materials of modern times and find numerous applications in critical engineering fields including aerospace, marine and automobile sector. Due to their increasing demand, it becomes apparently essential to employ advanced techniques, which can predict the long-term behavior of such materials in various in-service conditions. Epoxy and vinyl ester based composites are most commonly used in structural FRP composites. As each polymer has its own advantages and disadvantages, hybridization or blending of different polymers is a trending technology to improve the performance of resulting FRP composite. The present article aims at comparing the performance of glass fiber reinforced epoxy-vinyl ester interpenetrating polymer network (GEVIPN) composite with that of the base materials, i.e. glass fiber reinforced epoxy (GE) and glass fiber reinforced vinyl ester (GVE) composites. Flexural testing has been conducted at various in-situ temperatures (30 °C, 60 °C and 90 °C) where GEVIPN composite showed highest properties at 30 °C. The lifetime prediction of the composite materials has been carried out using accelerated deformation and time-temperature superposition (TTSP) principle. It was observed that GEVIPN composite showed highest creep resistance as compared to the other two composites at lower temperature, whereas opposite trend was observed at elevated temperature. At 30 °C, GEVIPN composite showed positive reinforcement efficiency for ∼385 days with respect to GE and ∼46.27 years with respect to GVE. Similar studies were done for the other reference temperatures. Following this, fractography analysis of the fractured surface was done under FESEM to identify the failure mechanisms and draw a comparison between the composites.

Failure analysis of fiberglass‐vinyl ester composite cylinders subjected to fire and asymmetric transient pressure

AbstractA hybrid numerical method is developed for failure prediction of glass fiber reinforced vinyl ester (GRV) composite cylinders subjected to fire and asymmetric transient pressure. The method is composed of layerwise theory, differential quadrature method, Fourier series expansion, and Newmark's time integration method. To achieve high‐accuracy solution, the char formation, resin decomposition, volatile convection, and temperature‐dependent material properties are considered. By comparing the developed results with the experimental and numerical results presented in the available literatures, the precision of this method is confirmed. The results reveal that although the polymeric composites are flammable, they are also strong thermal insulators compared to conventional metals, which reduces the flame spread rate from one section to another.

Mechanical behavior and dynamic damage constitutive model of glass fiber-reinforced Vinyl Ester with different fiber contents.

Glass fiber-reinforced plastics (GFRP) based on polymer materials are widely used in lightweight impac-resistant structure design. In the process of design and development, it is very important to clarify the mechanical behavior under dynamic load to improve the product performance. Therefore, in this paper, Quasi-stati and dynamic compression behaviors of unidirectional continuous glass fiber-reinforced vinyl ester (GF/VE) composites with five kinds of fiber contents in the fiber direction were measured by an electro-hydraulic servo experiment system and a split Hopkinson pressure bar, and damage evolution of the material is analyzed by observing the microstructure of the cross section of the material. Results show that: The content of glass fiber affects the wettability between fiber and matrix, and the failure mechanism of material at high strain rate; Under quasi-static conditions, higher glass fiber content yields greater failure strength; Under dynamic conditions, as glass fiber content increases, toughness decreases, and the peak stress first increases and then decreases. Finally, the nonlinear viscoelastic constitutive model with damage evolution is derived, which can be used to predict the impact resistance of new composite structures in the product development and design stage and reduce the development cycle.

Influence of Water Absorption on the Low Velocity Falling Weight Impact Damage Behaviour of Flax/Glass Reinforced Vinyl Ester Hybrid Composites.

Due to rigorous new environmental legislations, automotive, marine, aerospace, and construction sectors have redirected their focus into using more recyclable, sustainable, and environmentally friendly lightweight materials driven by strengthening resource efficiency drive. In this study, the influence of moisture absorption on flax and flax/glass hybrid laminates is presented with the aim to investigating their low velocity impact behaviour. Three different types of composite laminates namely, flax fibre reinforced vinyl ester, flax fibre hybridised glass fibre and glass fibre reinforced vinyl ester composites were fabricated using resin infusion technique. The moisture immersion tests were undertaken by immersing the different specimens in sea water bath at room temperature and 70 °C at different time durations. The low velocity falling weight impact testing was performed at 25 Joules of incident energy level and impact damage behaviour was evaluated at both ageing conditions using scanning electron microscopy (SEM) and X-ray microcomputed tomography (micro CT). The percentage of moisture uptake was decreased for flax vinyl ester specimens with glass fibre hybridisation. The maximum percentage of weight gain for flax fibre, flax/glass hybrid and glass fibre reinforced composites immersed at room temperature for 696 h is recorded at 3.97%, 1.93%, and 0.431%, respectively. The hybrid composite exhibited higher load and energy when compared flax/vinyl ester composite without hybridisation, indicating the hybrid system as a valid strategy towards achieving improved structural performance of natural fibre composites. The moisture absorption behaviour of these composites at room was observed to follow Fickian behaviour.

Enhancement of mechanical properties of glass fiber reinforced vinyl ester composites by embedding multi-walled carbon nanotubes through solution processing technique

This experimental study emphasizes the effect of the incorporation of multi-walled carbon nanotubes (MWCNTs) in conventional fiber reinforced-polymer composites on mechanical and thermal performance. Hand layup method was adopted for fabricating glass fiber reinforced vinyl ester (GVE), and 0.1 wt% MWCNTs filled GVE (MWCNT-GVE) composites. Bidirectional woven glass fiber (GF) and vinyl ester (VE) resin were used as reinforcement and matrix, respectively. The MWCNTs-VE suspension was prepared by solution processing technique. Mechanical properties were found to be affected by embedding MWCNTs in the neat GVE composite. MWCNT-GVE composite showed about a 7.37% increment in flexural strength and about 11.64% increment in tensile strength over neat GVE composite. Through differential scanning calorimetry (DSC), glass transition temperature (Tg), and the effect of MWCNTs on thermal properties of experimental composites were analyzed. A decrease in Tg value was observed after incorporating MWCNTs in GVE composite. Post failure, analysis was done by scanning electron microscope (SEM).

Durability of composite assemblies under extreme conditions: Thermomechanical damage prediction of a double-lap bonded composite assembly subject to impact and high temperature

The objective of this study is to simulate and predict the thermomechanical damage of composite material assemblies subjected to impact load while in a high temperature environment. Three-dimensional models were developed for a glass-fiber reinforced vinyl ester double-lap bonded composite assembly subject to combined mechanical and high thermal loads. Both thermal and mechanical models were implemented in the finite element analysis software Abaqus, using sequential heat transfer and dynamic implicit simulations. The thermal model is customized to properly simulate the thermal behavior of composites and generate accurate results while the mechanical model uses the existing functions of Abaqus. For a double-lap composite assembly, thermomechanical failure is predicted in the adhesive zone, at the adherent/adhesive interface, as the adhesive deteriorates at the early stages of exposure. The adherent also deteriorates but at a slower rate. Furthermore, stress concentration is observed at the edges of the stress distribution along the adhesive length, while the average stress along the length decreases gradually as a function of the fire exposure time. The conducted simulations made it possible to predict the stress distribution field variation as a function of time in the double-lap bonded assembly under a combined thermal-impact load. This would serve as a valuable tool for composite structure designers in sizing bonded composite assemblies for their structural projects, as the specifications for certain structures impose a time of evacuation of the structure during a shock and triggering of a fire.

Mechanical Properties of Submicron Glass Fiber Reinforced Vinyl Ester Composite

Vinyl ester (VE) resin inherently has intrinsic brittleness due to its high cross-link density. To improve mechanical performance, micro/nano fillers are widely used to modify this matrix. In present study, glass fiber in submicron scale at low contents was added into VE to prepare submicron composite (sMC). The impact resistance of un-notched sMC degraded with the increase of sGF content while that of notched-sMC remained the unchanged. Flexural properties of sMCs also were the same with that of neat resin. The results of Dynamic mechanical analysis (DMA) test showed the slight increase of storage modulus and the decrease of tan delta value in the case of sMC compared to those of un-filled matrix. However, the Mode I fracture toughness of sMC improved up to 26% and 61% corresponding to 0.3 and 0.6 wt% glass fiber used. The compact tension sample test suggests that there is the delay of crack propagation under tensile cyclic load in resin reinforced by submicron glass fiber. The number of failure cycle enlarged proportionally with the increment of sGF content in matrix.

Cutting performance of glass-vinyl ester composite by abrasive water jet

ABSTRACTPolymer matrix composite materials have been increasingly used in aerospace, defense, automotive and marine industries. In these fields, nontraditional machining method of abrasive water jet (AWJ) has been used significantly in order to form polymer matrix components. In this study, glass fiber reinforced vinyl ester composite plates have been investigated under various AWJ cutting parameters by using the Taguchi experimental design in detail. For Taguchi experimental design, experimental parameters of standoff distance, abrasive mass flow rate, traverse speed, pressure and material thickness were determined at three levels. Top kerf width and the surface roughness were investigated in order to understand the cutting performance. Finally, linear regression models were conducted and all performance parameters were examined using analysis of variance (ANOVA) and main effects plots. According to the overall test results, standoff distance was determined as the most effective one. The optimal parameter levels were obtained by the ‘main effects plots’, and finally, the predictive modeling was validated by performing the optimal combination of parameter levels.

Wear Performance Forecasting of Chopped Fiber–Reinforced Polymer Composites: A New Approach Using Dimensional Analysis

ABSTRACTSolid particle erosion of polymer matrix composites is a complex process in which wear occurs from the target surface by impingement of rigid sand particles in an air medium. The rate of material removal (RMR), also referred to as the erosion rate, mainly depends on target material parameters and the erosion conditions such as impact angle, impact velocity, and erodent size. A new semi-empirical model for prediction of the erosion rate of polymer matrix composites has been developed using a dimensional analysis technique based on Buckingham's π theorem. The predictive model analytically rests upon parameters related to chopped glass fiber composites, erodent (target material properties), and operating variables that mainly affect the erosion process of chopped glass fiber–vinyl ester resin composites. The forecasting ability of the predictive model has been assessed and verified by experimental investigations for chopped glass fiber–reinforced vinyl ester resin (VGF) composites. Validation of the theoretical erosion rates obtained from the predictive model showed that they were in good agreement with the experimentally determined erosion rates, where the average error range was estimated to be ∼10 to ∼20%.

Mechanical and thermal properties of glass fiber–vinyl ester resin composite for pipeline repair exposed to hot-wet conditioning

Fiber-reinforced composites are a well-recognized option for repair and rehabilitation of the pipelines for the oil and gas industry. Infilled composite sleeve system provides an effective rehabilitation solution, where the sleeve acts as prime reinforcement without any direct contact with steel. However, the long-term performance of the repair is dependent, in part, on the effect of hygrothermal ageing of the composites. In this publication, glass transition temperature and mechanical properties are compared for glass-fiber reinforced vinyl ester composite, both as-manufactured and after hot-wet conditioning at 80℃. The tensile and shear strength reduced substantially during conditioning, whilst the elastic modulus was relatively stable. The average glass transition temperature of the composite dropped from the as-manufactured value of 110℃ to 97℃ and 101℃, after 1000 and 3000 h of conditioning, respectively, indicating that it is stable and that the composite is suitable for use as a pipeline repair material operating at 80℃. The results indicate that a 1000 h conditioning period, specified as a minimum period in ISO/TS 24817 is suitable for representing long-term properties for stiffness-based designs for the composite material and conditioning temperature investigated.

Evaluation of the Effects of Fluids Upon the Flexural and Parallel-plate Loading Behavior of Glass Fiber Reinforced-vinyl Ester Resin Matrix Composite Pipes

Commercial glass fiber reinforced-vinyl ester resin composite pipes used in onshore and offshore utilities were exposed to the action of fluids that could normally come into contact with them during their service life, namely: salt water, biodiesel and a mixture of water and oil. The influence of these fluids upon the flexural properties and parallel-plate loading behavior of the composites was evaluated. The results of the mechanical tests point out that physical aging was the main phenomenon, and that it causes a reduction of stiffness of around 20-30% – at the parallel-plate test – and a decrease of toughness of up to 40% – at the flexural test. The results of the flexural tests were very dependent of the inhomogeneous microstructure of the commercial composite analyzed.

Desirability Fuzzy Multiple Criteria Optimization of Process Parameters in CNC Turning of GFRP/ Vinyl Ester Composites

Although, Glass fiber reinforced vinyl ester resin is used for the production of many electrical components, automotive structural parts, sporting goods and high performance marine equipments, very little is known about its machining aspects. In this study, a hybrid multiple criteria optimization algorithm involving desirability index and fuzzy inference system coupled with Taguchi methodology is used to evaluate the optimal cutting parameters setting, in order to satisfy contradictory requirements of quality and productivity. Woven fabric based GFRP/ Vinyl ester tubes are finish turned using PCD cutting tool. Four process parameters, each at three levels are selected for the study viz. cutting tool nose radius, cutting speed, feed rate and depth of cut. Individual desirability indices of the three performance measures, viz. surface roughness, tangential cutting force and material removal rate are converted into a single multi-performance characteristics index (MPCI) using fuzzy inference system, which is then optimized using Taguchi analysis.

The air-blast response of sandwich panels with composite face sheets and polymer foam cores: Experiments and predictions

The paper reports on an experimental and numerical investigation into the response of sandwich panels, with PVC foam cores and glass fibre reinforced vinyl ester face sheets, to localised blast loading. It also reports on the response of equivalent mass glass fibre reinforced vinyl ester panels. The loading was generated by detonating discs of plastic explosive at a small stand-off distance of 50 mm. Multiple failure modes were exhibited by the panels, including core compression, fragmentation and complete penetration, debonding between the face sheet and core, delamination between the fibre layers and rupture of the fibres. The sandwich panels exhibited complete penetration failure while no penetration occurred in the equivalent mass composite only panels. Reasonable agreement between the experimental results and numerical simulations is observed. The analysis reveals the reasons why the composite only panels perform better than the sandwich panels with PVC foam core. Due to the lower transverse stiffness of the individual components of the sandwich panel, considerably higher transverse velocity of the face sheet develops at the beginning of the process causing larger deflections and therefore larger in-plane stresses in the face sheet despite the high energy absorbing capacity of the foam core. The influence of the core density on the sandwich panel resistance to blast loading is also briefly discussed.

Ion‐leaching behaviors and corrosion morphology of glass fiber reinforced vinyl ester composites in sulfuric acid solution

AbstractThe corrosion mechanism of glass‐fiber reinforced vinyl ester composites was investigated by immersing composite samples in 40 wt% sulfuric acid solution at constant temperature of 35°C, 55°C, 65°C, and 75°C for periods up to 10,500 h. Results were characterized through weight gain tests, inductively coupled plasma analysis, and scanning electron microscope (SEM). Weight gains and ion‐leaching behaviors show that the composite interface has undergone significant changes due to a long corrosive environment, and the interface corrosion of composite increases with increasing the temperature. SEM images of surface and cross‐section of samples indicated that there exit in irreversible degradation reaction on resin matrix and interface in composite, which lead to the increase of weight gain and ion leachability, especially at high temperatures. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers

Influence of Carbon Nanotubes on Mechanical and Thermal Properties of Glass Fiber Reinforced Vinyl Ester Resin Composites

Carbon nanotubes (CNTs) were incorporated into glass fiber/ vinyl ester resins composites to improve their mechanical and thermal properties, especially the interlaminar shear and longitudinal compressive strengths which are belong to the matrix-dominanted properties and much weaker than the fiber-dominated properties. In this study, a higher temperature initiator was added to improve the polymerization degree and raise the transition temperature (Tg). Mechanical testing indicated that by adding 0.4 wt% CNTs, the nano-filled composites attributed to 21%, 16%, 10%, and 8% improvement in interlaminar shear strength, compressive strength, tensile strength and flexural strength with respect to their counterparts without CNTs, respectively. Moreover, Thermogravimetric analysis (TGA) also exhibits approximately 14°C higher decomposition temperature than those of conventional composites.

Natural Weathering and Sea Water Effects on the Durability of Glass Fiber Reinforced Vinylester: Fractographic Analysis

This paper presents a study of the effects of harsh outdoor weather and warm sea water on the tensile behavior of Glass-Fiber Reinforced Vinylester (GFRV) pipe materials destined for sea water handling and transportation. The effect of Dhahran’s outdoor weather for exposure periods ranging from 3 to 36 months revealed an improvement in tensile strength when compared with the as received GFRV sample. A significant increasing trend of tensile strength from 3 to 12 months was noted. This is attributed mainly to the post curing effects resulting in higher cross linking density. After 12 months of exposure the tensile strength showed a decreasing trend, but remaining still higher than the average tensile strength of as received (baseline) GFRV sample. Similar results of enhanced tensile strength were noted after immersion of GFRV pipes in warm Gulf sea water for 12 months. Fractographic analysis was performed on the tensile tested GFRV samples using optical microscope followed by scanning electron microscope (SEM). The characterization of the controlling failure mechanisms involved from fracture initiation to fracture propagation through the gage section of the specimen were predicted and were justified by correlating the optical and SEM pictures.

Prediction of the dynamic response of composite sandwich beams under shock loading

Finite element calculations are reported for the dynamic shock response of fully clamped monolithic and sandwich beams, with elastic face sheets and a compressible elastic–plastic core. Predictions of the peak mid-span deflections and deflected shapes of the beams are compared with the previously reported measured response of end-clamped sandwich beams, made from face sheets of glass fibre reinforced vinyl ester and a core of PVC foam or balsa wood [1]. Good agreement is observed, and the maximum sustainable impulse is also predicted adequately upon assuming a tensile failure criterion for the face sheets. The finite element calculations can also be used to bound the response by considering the extremes of a fully intact core and a fully damaged core. It is concluded that the shock resistance of a composite sandwich beam is maximised by selecting a composite with fibres of high failure strain.