Glass Fiber Reinforced Epoxy Composites Research Articles

Identification of failure mechanisms of metallised glass fibre reinforced composites under tensile loading using acoustic emission analysis

In this work, failure mechanisms of metallised glass fibre reinforced epoxy composites under tensile loading were investigated using acoustic emission analysis. Sandblasting with Al2O3 was used to pre-treat the composite surface prior to metallisation, and therefore to improve adhesion. The sandblasting time was varied from 2 s to 6 s. A two-step metallisation process consisting of electroless and subsequent electroplating was used for depositing the copper coating on the pre-treated composite surface. The mechanical pre-treatment had no significant negative effect on the mechanical properties of the composite laminate. The acoustic emission (AE) from the metallised composite was recorded during tensile testing in order to investigate the failure mechanisms. AE-Signals were analysed using pattern recognition and frequency analysis techniques. A correlation between the cumulative absolute AE-energy and the mechanical behaviour of uncoated and coated specimens during tensile testing was successfully observed. It was shown that a stronger adhesion between substrate and coating leads to a lower release of mechanical elastic energy, which could be recorded by means of AE analysis. Furthermore, differences in peak frequency, frequency distribution and the use of pattern recognition techniques allowed classifying the signal into three failure mechanisms for the uncoated samples and four failure mechanisms for the coated samples, namely matrix cracking, fibre-matrix interface failure, fibre breakage and substrate-coating interface failure. Waveform and frequency analysis of the classified signals supported the identification of the failure mechanisms. Furthermore, optical investigation and SEM images of the tested samples and fracture surfaces confirmed the identified mechanisms evaluated by acoustic emission analysis.

Processing and Mechanical Property Evaluation of Flax-Glass Fiber Reinforced Polymer Composites

In the fast developing world, the concern for the environmental pollution and the prevention of non-renewable and non-biodegradable resources has attracted researchers seeking to develop new eco-friendly materials and products based on sustainability principles. The fibers from the natural sources provide indisputable advantages over synthetic reinforcement materials such as low cost, low density, non-toxicity, comparable strength, and minimum waste disposal problems. In the present experimental study, flax and glass fibers reinforced epoxy composites are prepared and the mechanical properties of these composites are evaluated. The samples were subjected to the mechanical testing such as tensile, flexural and impact loading. Scanning electron microscope (SEM) analysis is carried out to evaluate fiber matrix interfaces and analyze the structure of the fractured surfaces.

Influence of micro and nanofillers on mechanical properties of pultruded unidirectional glass fiber reinforced epoxy composite systems

This paper reports, fabrication and characterization of unidirectional glass fiber reinforced epoxy composite filled with nano-size alumina, silica and micron-size alumina trihydrate fillers using pultrusion technique. Tensile, flexural and impact strengths were determined to evaluate the effectiveness of fillers on the mechanical properties. Results show that the micro and nanofillers act as secondary reinforcement. The tensile, flexural and impact strengths of 10 wt% (combined alumina, silica and alumina trihydrate)-filled glass fiber reinforced epoxy composite improved by 9, 20 and 28%, respectively, as compared to the unfilled and alumina/silica-filled glass fiber reinforced epoxy composites. The enhanced performance of micro and nanofillers-filled glass fiber reinforced epoxy composites is due to better adhesion and good dispersion of particulates in the epoxy matrix providing increased surface area for strong interfacial interaction and better load transfer. The improved mechanical properties indicate that the unidirectional glass fiber reinforced epoxy with combined micro- and nanofillers-filled composite is a good candidate for structural application.

ANALYSIS OF FATIGUE BEHAVIOR OF GLASS/CARBON FIBER EPOXY COMPOSITE

There are so many applications of composite materia ls in the past 20 years due to strong demand in mat erial performance set by technological developments, the use of composite ma terials has increased manifold. Most of these appli cations of the composite material are situations where the reduction in stre ngth and durability due to fatigue process is very likely. This work has been a great need in the exact fatigue properties of glass and carbon fiber reinforced epoxy composites. In t his study, both unidirectional carbon and glass fiber reinforced epoxy composites were detected for fatigue test by rotating bending machine.It was found that the probability distribution of the resistance fatigue of carbon fiber and glass fiber composite mate rials reinforced by fibers, at certain stress level, can be prepared by Weibull di stribution of two parameter with statistical co-re lation coefficient values greater than 0.80. Many methods were used to find oparameters of the Weibull distribution. Kolm ogorov-Smirnov goodness of fit was also used to amplify the results mention ed above. The Weibull distribution with two paramet ers is used to integrate the probability of default in the S-N relationship.

Design and strength analysis of glass fiber-reinforced epoxy composite shelter

In this study, glass fiber-reinforced epoxy composite (GFRP) plates were applied on the carriage panel skins of the shelter, which substituted the original aluminum plates. The main research objective is to prove that the application of GFRP plate on the shelter has absolute advantages and search the better lay-up design method to improve the structure strength of the shelter. The structure strength of the aluminum and GFRP shelters was studied, which was further investigated using finite element method under the given loading scenario. Finally, the computer simulations demonstrated that ±45° and 0° are more suitable for the laminate design, and ±45° should be put outside of the laminate. With the thickness of glass fiber decrease, more ±45° means higher strength of the laminate. To a certain degree, more 0°，90° and ±45°can make better stiffness. Besides, the quality of GFRP shelter has reduced 14.59% with using the lightweight material. Therefore, this research provides a reliable guidance for the production and design of GFRP shelter.DOI: http://dx.doi.org/10.5755/j01.mech.21.2.8624

Comparison of Mechanical Behaviour of Carbon and Glass Fiber Reinforced Epoxy Composites

An experimental study has been carried out to investigate tensile and bending properties of carbon ber (CFRE) and glass ber-reinforced (GFRE) epoxy composites. Three di erent ber orientations were applied, 0◦, 90◦ and [0◦, 90◦]. The laminates were obtained by manual lay-up process. The samples were evaluated by tensile tests according to the ASTM D3039 and bending tests according to the ASTM D790. Experimental results showed that maximum tensile strengths were observed at 0◦ ber direction for the both CFRE and GFRE composites. With respect to their tension properties, the CFRE samples had better performance than the GFRE samples, except for the 90◦ orientation. Three point bending tests proved that in all orientations CFRE composites had better performance, compared to GFRE composites.

Fault detection of composite beam by using the modal parameters and RBFNN technique

The detection of transverse cracks in terms of their location and intensity by using the radial basis function neural network (RBFNN) technique is analyzed in the current research and validated with experimental investigation. The glass fiber-reinforced epoxy composite is used in this research because of its valuable features, such as high stiffness and strength-to-weight ratios, good fatigue and wear resistance, and damage tolerance capability compared with isotropic material. The theoretical and numerical investigations are performed to obtain a relationship between the change in natural frequencies and mode shapes for the cracked and noncracked composite beam. Numerical analysis is performed by using the finite element software ANSYS on cracked and noncracked composite beams to measure the modal parameters, such as natural frequencies and mode shapes. These parameters are used to design an artificial intelligent controller based on the RBFNN-type neural network for predicting crack severity and its intensity. The relative natural frequencies and mode shapes (First, second, and third modes) of vibration are used as input data to the RBFNN controller, and the relative crack locations and crack depths are the output of RBFNN. Results from theoretical and numerical analysis are compared with the experimental results, and a good agreement is observed between them.

Effect of fiber surface texture on the mechanical properties of glass fiber reinforced epoxy composite

The effect of fiber sizing and surface texture on the strength and energy absorbing capacity of fiber reinforced composites has been evaluated at two length scales using the macromechanical quasi-static punch shear test and the micromechanical microdroplet test methods. E-Glass/SC-79 epoxy composite laminates with four different fiber sizing formulations with various degrees of chemical bonding and surface texture have been investigated. The failure modes during perforation and different energy dissipating damage mechanisms were identified and quantified. The punch shear strength and the total energy absorption per unit volume of composite with hybrid sizing have increased by 48% and 100% over the incompatible sizing. These results showed linear correlations with the interphase properties reported earlier by the authors (Gao et al., 2011) and provided a methodology for developing new sizing by tailoring chemical bonding and the fiber surface texture at the fiber–matrix interphase for improving both strength and energy absorption of composites.

Influence of cooling on the performance of the drilling process of glass fibre reinforced epoxy composites

Non-laminated composites find application in construction of bridges, ballistic applications, etc. However, literature on the drilling of non-laminated composite materials and literature on the drilling of thick composite materials under different cooling methods (dry, external and internal) is scarce. Hence the present study is aimed to investigate the influence of different cooling methods on quality characteristics (drill temperature and damage factor) while drilling glass fibre reinforced epoxy (GFRE) non-laminated 20mm thick pultruded composite rods having 80% fibre weight fraction and 0° fibre orientations with respect to the drill. The drilling experiments using TiN/TiAlN coated tungsten carbide twist drills of diameter 10mm were conducted using response surface methodology (RSM). The experimental values obtained for quality characteristics are empirically related to process parameters by developing a response surface model using Design-Expert software. The effects of process parameters on quality characteristics were analysed by using response surface graphs. The process parameters (feed, spindle speed and coolant pressure) are also optimized within the selected range. The optimal parameter levels are confirmed by validation test. From this investigation, it is evident that the internal cooling method is significant for obtaining high hole quality.

Effect of Alumina-Graphite Filler Blending on Tensile Behavior of Glass Fiber Reinforced Epoxy Composites

Effect of Alumina-Graphite Filler Blending on Tensile Behavior of Glass Fiber Reinforced Epoxy Composites

Theoretical analysis of interfacial debonding and fiber pull-out in fiber-reinforced polymer-matrix composites

A theoretical model is proposed to predict the interfacial debonding length and fiber pull-out length in fiber-reinforced polymer-matrix composites. The stress and displacement fields of fiber and matrix are derived considering the dual phase region model, and the relation between the pull-out length and debonding length of fiber is obtained. The interface debonding criterion is given based on the energy release rate relation in an interface debonding process. The formulas are applied in glass fiber-reinforced epoxy composites to demonstrate the newly theoretical model. The theoretical predictions of present model agree well with the experimental results. Several parameters studies are performed to analyze the debonding length and the pull-out length of fiber in glass fiber-reinforced epoxy composites.

An Investigation of Abrasive Water Jet Machining on Graphite/Glass/Epoxy Composite

In the present research work, the effect of abrasive water jet (AWJ) machining parameters such as jet operating pressure, feed rate, standoff distance (SOD), and concentration of abrasive on kerf width produced on graphite filled glass fiber reinforced epoxy composite is investigated. Experiments were conducted based on Taguchi’s L27 orthogonal arrays and the process parameters were optimized to obtain small kerf. The main as well as interaction effects of the process parameters were analyzed using the analysis of variance (ANOVA) and regression models were developed to predict kerf width. The results show that the operating pressure, the SOD, and the feed rate are found to be significantly affecting the top kerf width and their contribution to kerf width is 24.72%, 12.38%, and 52.16%, respectively. Further, morphological study is made using scanning electron microscope (SEM) on the samples that were machined at optimized process parameters. It was observed that AWJ machined surfaces were free from delamination at optimized process parameters.

Exposure Assessment of Particulate Matter from Abrasive Treatment of Carbon and Glass Fibre-Reinforced Epoxy-Composites - Two Case Studies

ABSTRACTThe use of composites is ever increasing due to their important structural and chemical features. The composite component production often involves high energy grinding and sanding processes to which emissions workers are potentially exposed. In this study we investigated the machining of carbon and glass fibre-reinforced epoxy composite materials at two facilities. We measured particle number concentrations and size distributions of the released material in near field and far field during sanding of glass- and carbon fibre-reinforced composites. We assessed the means of reducing exposure during the work by means of different working style, local exhaust ventilation, and enclosing the process area. Machining processes released particles primarily in < 100 nm size range. Without enclosure, process particle concentrations were 3.9 × 104 cm–3 in the near field and 1.3 × 104 cm–3 in the far field. Therefore workers in the same area may not be aware of being exposed to the process particles and the need of wearing protective outfits. Comparison of workers working style and effect on near field particle concentrations showed that a careless working style increased particle concentrations of 1.1% and 14.1% when comparing with a careful working style. Investigating the effect of the local exhaust ventilation showed that a maximum flow rate caused removal of close to 100% of particles from the working zone. A 28% reduction in the flow rate reduced particle removal efficiency more than 50%. With the enclosure around the process area, the process particle concentrations were 1.7 × 106 cm–3 in the near field, while the concentration in the far field was negligible. The enclosure used was shown to provide an average protection factor of more than 100.

Processing and Characterization of Glass-epoxy Composites Filled with Linz-donawitz (LD) Slag

Linz-Donawitz (LD) slag a major solid waste generated in huge quantities during steel making. It comes from slag formers such as burned lime/dolomite and from oxidizing of silica, iron etc. while refining the iron into steel in the LD furnace. Although a number of ways for its utilization have been suggested, its potential as a filler material in polymeric matrices has not yet been explored. The present work reports the possible use of this waste in glass fiber reinforced epoxy composites as a filler material. Hybrid composites consisting of bi-directional E-glass-fiber reinforced epoxy filled with different LD slag content (0, 7.5, 15, 22.5 wt%) are prepared by simple hand lay-up technique. The composites are characterized in regard to their density, porosity, micro-hardness and strength properties. X-ray diffractography is carried out in order to ascertain the various phases present in LDS. This work shows that LD slag, in spite of being a waste, possesses fairly good filler characteristics as it modifies the strength properties and improves the composite micro-hardness of the polymeric resin.

Ceramic particulate thermal barrier surface coatings for glass fibre-reinforced epoxy composites

This study investigates the thermal barrier efficiency of five commercially available ceramic nano and micro particles deposited on the surfaces of glass fibre-reinforced epoxy composites (GRE). Two approaches of application of deposition of ceramic particles have been undertaken, firstly where the ceramic particles were dispersed in a phenolic resin binder and applied on a GRE surface by a K-bar coater and the second where extra ceramic particles were sprayed on the first coating while the resin was partially cured to enable the surface to be completely covered by ceramic particles, leaving no resin exposed. The thermal barrier efficiency of these coatings was evaluated from the cone calorimetric parameters at incident heat fluxes of 35 and 50 kW/m2 as well as from temperature gradient through the samples’ thicknesses, measured by inserting thermocouples on the exposed and back surfaces during the cone tests. The morphology and durability of the coatings to water absorption, peeling, impact and flexural loading were also studied. The results showed that the surface layers of all coated samples were uniform and there was a strong adhesion between the coating and the substrate. Moreover, they did not adversely affect the mechanical properties of GRE composite while improving the mechanical property retention of GRE composites after exposure to heat.

유리섬유강화 에폭시 레진 복합체의 기계적, 유전체 특성에 미치는 첨가제 함유 에폭시 영향

Three different types of additives, thiokol, epoxidized natural rubber (ENR) and epoxidized linseed oil (ELO), were dispersed in an epoxy matrix before being used in glass fiber (GF) composites, and their effects on the mechanical and dielectric properties of epoxy resin and glass fiber reinforced epoxy composites (GF/EP) were examined. The addition of each of 7 phr ENR, 9 phr ELO and 5 phr thiokol into the epoxy resin increased the fracture toughness significantly by 56.9, 43.1, and 80.0%, respectively, compared to the unmodified resin. The mode I interlaminar fracture toughness of the GF/EP at propagation was also improved by 26.9, 18.3 and 32.7% when each of 7 phr ENR, 9 phr ELO, and 5 phr thiokol, respectively, was dispersed in the epoxy matrix. Scanning electron microscopy showed that the additives reduced crack growth in the GF/EP, whereas their dielectric measurements showed that all these additives had no additional effect on the real permittivity and loss factor of the GF/EP.

UV-polymerisable, phosphorus-containing, flame-retardant surface coatings for glass fibre-reinforced epoxy composites

Abstract A vinyl phosphonic acid based flame retardant coating has been applied on the surface of a glass-fibre reinforced epoxy (GRE) composite substrate using a UV polymerisation technique. On exposure to heat the poly (vinyl phosphonic acid) (PVPA) coating thus obtained, intumesces and acts as a thermal insulator, providing active fire protection to the composite structure. Samples with ∼300 and 500 μm thick coatings were prepared. The fire performance of the coated GRE composite was studied by cone calorimetry at 35 and 50 kW/m 2 heat fluxes. While the sample with ∼500 μm thick coating did not ignite at both heat fluxes, the one with the ∼300 μm thick coating ignited at 50 kW/m 2 , however the time-to-ignition was delayed from 60 s in the uncoated sample to 195 s and the peak heat release rate reduced from 572 kW/m 2 to 86 kW/m 2 . The coatings did not peel off when subjected to a tape pull test and resisted cracking/debonding during an impact drop test of up to 5 J energy. However, the coatings are hydrophilic, showing significant mass loss in a water soak test. The improvement of the hydrophobicity of these coatings is a focus of our future research.

Evaluation of Adhesion Improvement of a GFRP Treated with Atmospheric Plasma Torch

The applications (and repair) of glass fiber reinforced epoxy composites are increasing in different industries (wind turbines, boats, chassis of buses, etc.) due to specific strength and low cost. Their major disadvantage is the difficulty to shape complex components. This problem can be solved manufacturing different parts, being adhesively bonded afterwards. This work studies the effect of atmospheric pressure plasma torch compared to grit-blasting to improve adhesion. After surface treating different parts, the changes of wettability and surface energy were measured. Treated samples were bonded with polyurethane and epoxy adhesives, and the quality of the bond was evaluated using pull-off adhesion tests and fracture strength test under cleavage loads. Obtained results allow to select the most adequate treatment in terms of mechanical requirements.

Effect of fiber orientation on the shear behavior of glass fiber/epoxy composites

This paper deals with the study of the influence of the lay-up configuration on interlaminar and in-plane shear properties of glass fiber reinforced epoxy composites. The following laminates were produced by resin transfer molding with vacuum assistance for this study: [0]5, [90]5, [0/90/0/90/0] and randomly oriented (mat). The composites, with similar overall fiber volume fraction, were evaluated based on four tests: double-notched shear, short beam shear, V-notched rail and Iosipescu shear tests. Besides, the dynamic shear modulus was measured with non-destructive testing based on free vibration method. The [0]5 laminate presented interlaminar shear strength almost twice that of [90]5, whereas the mat samples presented higher in-plane shear strength in both tests used due to its random fiber orientation. The dynamic shear modulus was higher for the composites [0]5, as expected due to the longitudinally oriented fibers. Among the shear test methods applied, double-notched and V-notched methods exhibited more auspicious features, possibly due to a more uniform shear stress state during testing.

Toughness, flexural, damping and interfacial properties of hybridized GFRE composites with MWCNTs

As the improved damping in fiber-reinforced composites can affect the other mechanical properties, therefore, the aim of this work is to investigate the effect of multiwall carbon nanotube (MWCNT) on the interfacial bond strength, flexural strength and stiffness, toughness and damping properties of hybridized glass-fiber reinforced epoxy (GFRE) composites. Nanophased epoxy resin was used to hybridize unidirectional and quasi-isotropic GFRE composites with [0/±45/90]s and [90/±45/0]s stacking sequences. Results from the interfacial characterizations of the hybridized composites showed improvement up to 30% compared to the control laminates. Hybridization of GFRE laminates with MWCNTs leads to decreasing the flexural and storage moduli, increasing flexural strength, toughness, natural frequencies and damping ratio. A high correlation coefficient of 0.9985 was obtained between static flexural and dynamic storage moduli. The highest flexural strength, flexural and storage moduli and natural frequency of quasi-isotropic laminate were observed for [0/±45/90]s stacking sequence and vice versa for damping ratio.