Volume Fraction Of Glass Fibers Research Articles

Fracture behaviour of glass fibre-reinforced polyester composite

Fracture toughness and critical energy release rate of polyester-reinforced glass fibres were investigated using linear elastic fracture mechanics approach. The effect of fibre volume fraction of chopped strand mat glass fibres in the matrix on the composite properties was considered. Finite-element analysis using FRANC2D/L was adopted for further verification. The results showed a dramatic increase in the values of fracture toughness and critical energy release rate with increasing fibre content. 60% vf of glass fibres enhanced the fracture toughness and critical energy release rate properties of neat polyester by ∼ 22-fold and 1200-fold, respectively. The numerical results showed an agreement with experimental ones.

繊維強化プラスチックの破壊モード特性に関するマイクロメカニクス

Discontinuous fiber reinforced plastics have superior productivity and formability in comparison with continuous fiber reinforced plastics. However, their strengths are remarkably low. Thus there is an urgent need to establish a fundamental model in order to improve the strength of discontinuous fiber reinforced plastics. In the present work, we utilized numerical simulations that consider the microscopic damage in the composite and incorporate an individual constitutive law of thermosetting resin or thermoplastic resin. The fundamental mechanism that affected the strength and failure of the composite was investigated when the fiber length and/or matrix properties were varied from continuous glass fiber reinforced plastics to discontinuous glass fiber reinforced plastics. Our results clarified two factors that cause the strength degradation of discontinuous fiber reinforced plastics. One is the low yield stress of thermoplastic resin, which is frequently used for the matrix of discontinuous fiber reinforced plastics. As the other factor, the final failure mode is changed from fiber breaking mode to matrix cracking mode in the case of the low fiber volume fraction of discontinuous glass fiber reinforced plastics. Moreover, we investigated the relationship between fiber length and strength of carbon fiber reinforced polypropylene and the effect of thermoplastic matrix properties depending on the loading rate as well.

Mechanical Behavior of Unidirectional Glass Fibers Reinforced Resol/VAC‐EHA Composites at Different Volume Fraction of Fibers

Glass fibers reinforced Resol/VAC‐EHA Composites were fabricated at different volume fraction of fibers to determine the mechanical behavior. Resol solution was blended with vinyl acetate‐2‐ethylhexyl acrylate (VAc‐EHA) resin in an aqueous medium with varying volume fraction of glass fibers. The role of fiber/matrix interactions in glass fibers reinforced composites were investigated to predict the stiffness and damping properties and their different mechanical behavior was compared with pure Resol and Resol/VAC‐EHA blend. In order to study the static and dynamic response of Resol, Resol/VAC‐EHA blend, and glass fibers reinforced composites, a multiquadric radial basis function (MQRBF) method was developed. MQRBF was applied for spatial discretization and a Newmark implicit scheme was used for temporal discretization. The discretization of the differential equations generates a larger number of algebraic equations than the unknown coefficients. To overcome this ill conditioning, the multiple linear regression analysis, which is based on the least square error norm, was employed to obtain the coefficients. Simple supported and clamped boundary conditions were considered. Numerical results were compared with those obtained by other analytical methods.

Studies on Tensile and Flexural Properties of Short Banana/Glass Hybrid Fiber Reinforced Polystyrene Composites

The interest in natural fiber-reinforced polymer composites is growing rapidly due to its high performance in terms of mechanical properties, significant processing advantages, excellent chemical resistance, low cost, and low density. The development of composite materials based on the reinforcement of two or more fiber types in a single matrix, which leads to the production of hybrid composites. In the field of technical utilization of plant fibers, banana fiber-reinforced composites represent one of the most important areas. The influence of fiber content, fiber loading, and hybrid effect on the mechanical properties such as tensile strength, Young's modulus, elongation at break, and flexural properties of the composites, was evaluated. The volume fraction of glass fiber based on total fiber content increases all the mechanical properties, except elongation at break. The tensile and flexural properties of composites are observed to have improved as the fiber loading (vol%) increases. On the other hand, lack of good interfacial adhesion and poor resistance to moisture absorption make the use of natural fiber-reinforced composites less attractive. Modification of the banana fiber improves the optimum fiber-matrix properties. Hybrid effect was calculated using additive rule of hybrid mixtures. The comparison of theoretical and experimental values of tensile properties was determined using a number of models. All the models except parallel show good agreement with the experimental results.

Mechanical properties and water sorption behavior of phenol–formaldehyde hybrid composites reinforced with banana fiber and glass fiber

AbstractBanana fiber, which is rich in cellulose, relatively inexpensive, and abundantly available, has potential for polymer reinforcement. This study explores the merits of combining high‐modulus glass fibers with banana fiber in phenolic resoles to develop high‐performance, cost‐effective, lightweight hybrid composites. Of particular interest is the effect of varying layering patterns of banana fiber and glass fiber on the tensile, flexural, and impact properties of hybrid composites. The highest tensile strength value has been obtained for an intimate mixture of both fibers, and the maximum flexural and impact strength has been obtained for composite samples prepared from interleaving layers of banana fiber and glass fiber. Tensile, flexural, and impact properties of the composites increase with an increasing volume fraction of glass fiber. The water uptake of these composites decreases with the incorporation of glass fiber into banana fiber, and the composites with glass fiber at the periphery and banana fiber at the core have the maximum resistance to water absorption. Scanning electron micrographs show the fracture mechanism and fiber/matrix adhesion in these composites © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Electrical properties of banana fiber‐reinforced phenol formaldehyde composites

AbstractThe electrical properties of banana fiber‐reinforced phenol formaldehyde composites have been studied with special reference to fiber loading, fiber treatments, and hybridization with glass fibers. The dielectric constant decreased with frequency and fiber loading. Treatments with silanes, NaOH and acetylation, latex treatment, heat treatment, and cyanoethylation decreased the dielectric constant value. The dielectric constant is higher for banana/PF composites than that of glass/PF composites. In hybrid composites, the dielectric constant decreased with increase in glass fiber concentration. The volume resistivity of banana fiber‐reinforced phenol formaldehyde composites decreased with frequency and fiber loading. Chemical modifications in the fiber increased the volume resistivity of the composites. Volume resistivity of banana/glass hybrid composites increased with increase in glass fiber content. Layered composites with glass fiber at periphery were found to have higher volume resistivity than other layering patterns. The loss factor decreased by the chemical treatments and in hybrid composites it decreased with increase in volume fraction of glass fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Mechanical properties of injection molded long fiber polypropylene composites, Part 1: Tensile and flexural properties

AbstractInnovative polymers and composites are broadening the range of applications and commercial production of thermoplastics. Long fiber‐reinforced thermoplastics have received much attention due to their processability by conventional technologies. This study describes the development of long fiber reinforced polypropylene (LFPP) composites and the effect of fiber length and compatibilizer content on their mechanical properties. LFPP pellets of different sizes were prepared by extrusion process using a specially designed radial impregnation die and these pellets were injection molded to develop LFPP composites. Maleic‐anhydride grafted polypropylene (MA‐g‐PP) was chosen as a compatibilizer and its content was optimized by determining the interfacial properties through fiber pullout test. Critical fiber length was calculated using interfacial shear strength. Fiber length distributions were analyzed using profile projector and image analyzer software system. Fiber aspect ratio of more than 100 was achieved after injection molding. The results of the tensile and flexural properties of injection molded long glass fiber reinforced polypropylene with a glass fiber volume fraction of 0.18 are presented. It was found that the differences in pellet sizes improve the mechanical properties by 3–8%. Efforts are made to theoretically predict the tensile strength and modulus using the Kelly‐Tyson and Halpin‐Tsai model, respectively. POLYM. COMPOS., 28:259–266, 2007. © 2007 Society of Plastic Engineers

BEHAVIOR OF WOVEN FABRIC REINFORCED EPOXY COMPOSITES UNDER BENDING AND COMPRESSIVE LOADS

The mechanical behavior of epoxy reinforced by three different types of woven fibers was studied under compressive and bending loads. The reinforcements used were: woven glass fibers (volume fractions: 9.2%, 18.4%, 27.6%, and 36.8%), woven carbon fibers, and woven hybrid (carbon/glass) fibers at 36.8 vol.%, each. The composites were manufactured using the hand lay-up technique. Pure (unreinforced) epoxy specimens were tested as a reference material. The fracture behavior of the investigated specimens was studied both macroscopically, and using scanning electron microscopy (SEM). It was found that under compressive loads, elastic deformation is nonlinear for pure epoxy as well as epoxy reinforced by low volume fractions of glass woven fibers. At high volume fractions of glass fibers, carbon fibers, or hybrid ones, this non linearity diminished significantly. The modulus of elasticity of epoxy-reinforced by glass fibers (GF) continued to increase as a function of fiber volume fraction. At 9.2 vol.% the modulus of elasticity showed an increase of 65% compared to pure epoxy, while at 36.8 vol.% GF the improvement reached 117%. At the same volume fraction of 36.8% hybrid, and carbon reinforcements the improvements were 160%, and 178%, respectively. Similar trend of improvements were observed for the other mechanical properties under compressive loads. Under bending loads, both the flexure modulus, and flexure strength showed significant improvement as a function of glass fiber volume fraction. At the same reinforcement volume fraction, carbon fiber composites gave the highest mechanical properties, followed by hybrid composites, while glass fiber composites showed lowest improvement (about 348% improvement in flexure strength compared to pure epoxy). Fiber pull-out and debonding are the main fracture mechanisms for glass fiber reinforced epoxy, while interlaminar shearing is the main mechanism for carbon fiber composites. Hybrid (C/G) composites showed a mixed mode mechanism. The fracture process in bending proceeded in stages from the tension side inwards towards the compression side. Each stage is associated with a load drop and audible sound waves.

Mechanical Properties and Swelling Behavior of Short Glass Fiber Reinforced Polyester Composites

Chopped strand glass fiber reinforced particle-filled polymer composite with different volume fractions of glass fibers has been investigated for tensile strength. Both the properties have been studied with respect to varying fiber content i.e., from 1 to 10%. In addition, the effect of various acids, alkalies, and solvents has been investigated. It has been found that fiber reinforcement increases the chemical absorption. Swelling studies have also been done for NaCl (15%) and distilled water, and the diffusivity coefficient and sorption coefficient are calculated. The sorption coefficient increases with increasing fiber content while the diffusivity coefficient decreases with increasing fiber content.

A PMMA composite as an optical diffuser in a liquid crystal display backlighting unit (BLU)

The effect of thermo-physical properties, relative humidity and stiffness on the warpage of a poly(methyl methacrylate) (PMMA) diffusing plate modified with glass fibers in a direct-lit backlight unit (BLU) of a liquid crystal display (LCD) was investigated. The warpage of the PMMA diffusing composites modified with a glass fiber were significantly reduced relative to that of a conventional PMMA diffusing plate. Luminance and scattering characteristics of the PMMA diffusing composites having 5, 10, 20 vol% of glass fibers were measured. Although the luminance of the composite was lowered as increasing the volume fractions of glass fibers in the PMMA composites, good brightness uniformity of the composites on a light source was obtained.

섬유함유율에 따른 GF/PP 복합재료의 인장파괴거동

The main goal of this work is to study the effect of glass fiber volume fraction on the result of tensile test with respect to glass fiber/polypropylene(GF/PP) composites. The tensile test and failure mechanisms of GF/PP composites were investigated in the fiber volume fraction range from 10% to 30%. The tensile strength and the fracture strength increased with the increasing of the fiber volume fraction in the tested range. Fiber pull-out and debonding of this composites increased with the fiber volume fraction in thc tested range. The major failure mechanisms were classified into the debonding, the fiber pull out, the delamination and the matrix deformation.

Ultrasonic Riveting and Hot-Air-Sticking of Fiber-Reinforced Thermoplastics

Mechanical fastening, e.g. screwing or riveting, or thermal joining techniques like ultrasonic riveting or hot-air-sticking, are used to join thermoplastic composites and metallic structures. This paper compares the experimental results of ultrasonic riveting and hot-air sticking of fiber-reinforced polypropylene (PP-GM30, PP-LGF40) and polyamide6 (PA6-GF30) with steel. The influence of glass fiber volume fraction on process stability and the tensile strength of the joint are evaluated from micrographs and X-ray photographs. The influence of the thermoplastic matrix material and the glass fiber length on the wear of the sonotrode during ultrasonic riveting is investigated based on SEM-micrographs and surface roughness measurements.

Fracture behavior of glass fiber reinforced polymer composite

Chopped strand glass fiber reinforced particle-filled polymer composite beams with varying notch-to-depth ratios and different volume fractions of glass fibers were investigated in Mode I fracture using three-point bending tests. Effects of polyester resin content and glass fiber content on fracture behavior was also studied. Polyester resin contents were used 13.00%%, 14.75%, 16.50%, 18.00% and 19.50%, and glass fiber contents were 1% and 1.5% of the total weight of the polymer composite system. Flexural strength of the polymer composite increases with increase in polyester and fiber content. The critical stress intensity factor was determined by using several methods such as initial notch depth method, compliance method and J-integral method. The values of K IC obtained from these methods were compared.

Melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites. I. Untreated fibers

AbstractThe melt rheological behavior of intimately mixed short sisal–glass hybrid fiber‐reinforced low‐density polyethylene composites was studied with an Instron capillary rheometer. The variation of melt viscosity with shear rate and shear stress at different temperatures was studied. The effect of relative composition of component fibers on the overall rheological behavior also was examined. A temperature range of 130 to 150°C and shear rate of 16.4 to 5470 s−1 were chosen for the analysis. The melt viscosity of the hybrid composite increased with increase in the volume fraction of glass fibers and reached a maximum for the composite containing glass fiber alone. Also, experimental viscosity values of hybrid composites were in good agreement with the theoretical values calculated using the additive rule of hybrid mixtures, except at low volume fractions of glass fibers. Master curves were plotted by superpositioning shear stress and temperature results. The breakage of fibers during the extrusion process, estimated by optical microscopy, was higher for glass fiber than sisal fiber. The surface morphology of the extrudates was analyzed by optical and scanning electron microscopy. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 432–442, 2003

Surface quality and shrinkage of the composite bus housing panel manufactured by RTM

Resin transfer molding (RTM) process has been widely used in automobile industries, because products with large area can be manufactured easily with lower manufacturing cost than that of compression molding or hand lay up method. Although composite structures manufactured by RTM have light weight, good dynamic and impact characteristics, the low surface quality of composite structures made by RTM often hinders the adoption of composite automotive panels because parts made of glass fiber mat and unsaturated polyester often have shrinkage and warpage problems. To investigate the relationship between the shrinkage and the surface quality of composite part, in this work, the formation of surface contour line and the surface quality were measured experimentally with respect to stacking sequence and fiber volume fraction of glass fiber. Based on the results obtained, a real size composite bus housing panel was successfully manufactured.

Long-Term Creep of Hybrid Aramid/Glass-Fiber-Reinforced Plastics

The results of experimental investigation of the long-term creep of SVM aramid fibers, EDT-10 epoxy resin, aramid-epoxy FRP (fiber-reinforced plastics), glass-epoxy FRP, and aramid/glass-epoxy hybrid FRP with different volume fractions of aramid and glass fibers are presented. The long-term tests were continued for 50,000 h (5.7 years). A structural approach for predicting the long-term creep from the properties and content of the components is considered. The effect of hybridization (partial replacement of the aramid fibers by glass fibers) on the inelastic deformation of hybrid FRP is discussed. The redistribution of stresses in the components during long-term creep of the hybrid composites is analyzed.

Determination of Short Glass-Fiber Volume Fractions in Compression Molded Thermoset Composites—Experimental

Prediction of volume fraction of short glass-fibers in compression molded thermoset composites parts such as sheet molding compounds (SMC) is of importance since their distribution affects the mechanical property and surface quality. In the present study, a simple approach based on digital image processing technique was applied in determining the fiber volume fraction distribution in the compression molded flat plate of SMC. Although the present digital image processing approach does not have the resolution to distinguish individual fiber diameters, it is capable of determining fiber concentrated regions, and thus an effective means of determining the global distribution of fibers in a single process is provided. As molding conditions, two different molding temperatures and velocities as well as two different compression ratios were investigated to determine the influence of molding parameters on the glass-fiber volume fraction distributions. It was found that a rather uniform distribution of glass-fibers was obtained under the condition with smaller compression ratios and faster mold closing speeds, whilst the effect of mold temperature on volume fraction distribution being negligible. The validity of the proposed scheme was estimated by comparing the predicted volume fraction distribution with the experimental result obtained from the conventional burning-test measurement. The comparison clearly demonstrates the simplicity and capability of the digital image processing technique applied under the present condition.

Determination of Short Glass-Fiber Volume Fractions in Compression Molded Thermoset Composites—Numerical

In this paper, a fiber content prediction model was investigated in order to numerically determine the glass-fiber volume fraction distributions by approximating the compression molded thermoset composites as a rigid-thermoviscoplastic material. The current approach of fiber distribution prediction was compared to the results based on mass balance and isothermal analysis, respectively, for the case of simple flat-plate compression molding of sheet molding compounds (SMC). From this comparison it was found to better reproduce the trend of fiber distributions observed in experimental findings. The two flow coefficients involved with the current model in characterizing the flow of fibers during compression molding were determined by a numerical search scheme in the present investigation, based on minimizing the errors between the numerically predicted values and the measured data obtained from the image processing. Comparison of isothermal and non-isothermal finite element simulations revealed the importance of the effects of heat transfer during compression molding and showed that the current approach provides useful information about the local variation of fiber volume fractions. Following this approach, it will be possible to make better estimates of the distribution of fibers in compression molded thermoset composites parts with complex geometries.

The Static Tensile Strengths of a Random Chopped Glass/Polypropylene Composite Estimated by a Percolation Model.

The static strength of a quasi-isotropically reinforced random chopped glass/polypropylene composite is studied theoretically and experimentally. In the previous paper(1) a fracture model is proposed which simulates probabilistically the damage accumulation process. On the basis of the percolation theory, the model can estimate the static strength of the FRPP as the critical point on condition that the fiber volume fraction is 30%wt. In this paper, by applying the model, the strengths of a discontinuous fiber composite are predicted as a function of the volume fraction of glass fiber. By comparing with the experimental data, the validity of the model is confirmed in terms of the fiber volume fraction.

Helium permeation in composite materials for cryogenic application

Glass fibre composites are attractive alternatives to metals for cryogenic applications because of their high specific strength and stiffness and their low electrical and thermal conductivity. A disadvantage is the ease of permeability of He through the material at room temperature, and after damage accumulation at 4.2 K. For this study, a special experimental leak detector was built based on a controlled helium flow through a diaphragm and mass spectroscopic measurement. Temperature cycles between room temperature (RT) and 77 K have no effect on permeation rates at 300 K. Tensile tests producing damage at room temperature showed different effects on permeation flow of He, caused by cracking. At 4.2 K, the limit for using this material is given by matrix cracking. The glass fibre volume fraction is preponderant in controlling the coefficient of He permeation. It has been found that composite materials such as glass fibre reinforced epoxy can be used effectively for cryogenic applications using a vacuum as thermal insulation.