Increasing Carbon Fiber Content Research Articles

Shape memory performance of asymmetrically reinforced epoxy/carbon fibre fabric composites in flexure

In this study asymmetrically reinforced epoxy (EP)/carbon fibre (CF) fabric composites were prepared and their shape memory properties were quantified in both unconstrained and fully constrained flexural tests performed in a dynamic mechanical analyser (DMA). Asymmetric layering was achieved by incorporating two and four CF fabric layers whereby setting a resin- and reinforcement-rich layer ratio of 1/4 and 1/2, respectively. The recovery stress was markedly increased with increasing CF content. The related stress was always higher when the CF-rich layer experienced tension load locally. Specimens with CF-rich layers on the tension side yielded better shape fixity ratio, than those with reinforcement layering on the compression side. Cyclic unconstrained shape memory tests were also run up to five cycles on specimens having the CF-rich layer under local tension. This resulted in marginal changes in the shape fixity and recovery ratios.

Effects of initial fiber length and fiber length distribution on the properties of carbon-fiber-reinforced-polypropylene composites

In this study, short carbon fiber-reinforced polypropylene composites with three different initial carbon fiber lengths were prepared by using extrusion compounding and injection molding techniques. The physical and morphological properties of the prepared short carbon fiber-reinforced composites were investigated by means of tensile test, differential scanning calorimetry and scanning electron microscopy. Final fiber length distributions of composites were also determined by using an image analyzing program. It was found that the maximum number of fibers was observed in the range from 51 to 100 µm. Number average final fiber lengths were calculated between 230 and 280 µm. Regardless of the used initial carbon fiber length, tensile strength and modulus values of the composites increased with the increasing carbon fiber content. It has been concluded that the initial fiber length at the studied range did not have any significant effect on the properties of composites.

Synergism of carbon fiber and polyimide in polytetrafluoroethylene-based composites: Friction and wear behavior under sea water lubrication

Polytetrafluoroethylene-based (PTFE-based) composites reinforced simultaneously with carbon fiber (CF) and polyimide (PI) of different volume fractions were prepared. The microstructure and phase composition of as-prepared PTFE-based composites were analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Besides, their friction and wear behavior under sea water lubrication was evaluated in relation to the synergistic effect between CF and PI using a ring-on-block test rig, and their worn surfaces were also analyzed using SEM. Results showed that the incorporation of PI induced loosening of the microstructure of PTFE but increased the wear resistance. Contrary to the above, the incorporation of CF led to increased compactness of PTFE, and the compactness as well as wear resistance of the PTFE-based composites increased with the increase of CF content. More importantly, the simultaneous incorporation of PI and CF at a proper volume fraction led to drastically reduced wear rate of PTFE under sea water lubrication. This implies that there exists synergistic friction-reducing and wear-resistant effect between PI and CF. As a result, the PTFE-based composite containing 5% PI (volume fraction) and 15% CF had the best wear resistance, showing promising application in ocean environment.

Preparation and characterization of poly(vinyl chloride)–continuous carbon fiber composites

AbstractIn this article, we report on the preparation and characterization of novel poly(vinyl chloride) (PVC)–carbon fiber (CF) composites. We achieved the reinforcement of PVC matrices with different plasticizer contents using unidirectional continuous CFs by applying a warm press and a cylinder press for the preparation of the PVC–CF composites. We achieved considerable reinforcement of PVC even at a relatively low CF content; for example, the maximum stress (σmax) of the PVC–CF composite at a 3% CF content was found to be 1.5–2 times higher than that of the PVC matrix. There were great differences among the Young's modulus values of the pure PVC and PVC–CF composites matrices. The absolute Young's modulus values were in the range 1100–1300 MPa at a 3% CF content; these values were almost independent of the plasticizer content. In addition, we found a linear relationship between σmax and the CF content and also recognized a linear variation of the Young's modulus with the CF content. The adhesion of CF to the PVC matrix was strong in each case, as concluded from the strain–stress curves and the light microscopy and scanning electron microscopy investigations. The mechanical properties of the PVC–CF composites with randomly oriented short (10 mm) fibers were also investigated. At low deformations, the stiffness of the composites improved with increasing CF content. Dynamic mechanical analysis (DMA) was used to determine the glass‐transition temperature (Tg) of the PVC–CF composites. The high increase in the Young's modulus entailed only a mild Tg increase. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Hybrid Fibre Reinforced Epoxy Composites for Pultrusion: Mechanical and Thermal Properties

Hybrid glass/carbon fibre reinforced epoxy (GF/CF/Epoxy) composites have been manufactured by pultrusion processes, in order to obtain the best mechanical properties, thermal properties and optimum price of hybrid GF/CF/Epoxy composites for pultrusion. The static mechanical properties including flexural strength, flexural modulus, notched Izod impact strength and swelling ratio, the dynamic mechanical properties including dynamic storage modulus, E’ and tan δ (T), and the thermal properties including of weight loss by TGA of pultruded hybrid GF/CF/Epoxy composites were investigated. The results showed that the flexural modulus increased with the increasing of carbon fibre content. The flexural strength, notched Izod impact strength and swelling ratio of pultruded composites decreased with increasing carbon fibrecontent. The E’ of pultruded composites increased with the carbon fibre content, postcuring temperature and postcuring time. The peak of tanδ for pultruded composites was shifted to a higher temperature when the carbon fibre content, postcuring temperature, and postcuring time were increased. From TGA, the weight loss of pultruded composites decreased with the carbon fibre content, postcuring temperature, and postcuring time in an inert (N2 gas) atmosphere, and the char yield increased with the carbon fibre content, postcuring temperature, and postcuring time. From the SEM morphology, excellent wet-out of the hybrid fibre by the epoxy resin could be observed.

Effects of maleated polypropylene on the morphology, thermal and mechanical properties of short carbon fiber reinforced polypropylene composites

The aim of this study was to determine the effect of the maleic anhydride grafted polypropylene (PP-g-MAH) on the properties of short carbon fiber (CF) reinforced polypropylene (PP) composites. The composites were prepared by melt blending and injection molding techniques at different percentages of CF. Tensile tests, hardness, differential scanning calorimeter (DSC) and scanning electron microscopy (SEM) were performed to characterize the physical and morphological properties of the prepared composites. It was observed from SEM photographs that modification with PP-g-MAH improved the interfacial adhesion between the carbon fibers and PP matrix. The ultimate tensile strength, hardness and modulus values of modified PP composites were higher compared to the values of CF reinforced PP composites. Melting temperature of all composites was not changed significantly with increasing CF content; however degree of crystallinity values were decreased with the increasing CF content level.

Mechanical Properties of Csf/AZ91D Composites Fabricated by Extrusion Forming Process Directly Following the Vacuum Infiltration

Magnesium matrix composites are attractive for weight critical application, such as automotive and aerospace components, because of its high specific strength and stiffness. Extrusion process directly following vacuum infiltration (EVI) can eliminate the porosity and obtain the well-aligned and uniform fiber distribution during the fabrication of Csf/AZ91D composite. This process combines the advantages of gas pressure infiltration, squeeze casting, and semi-solid extrusion. The mechanical properties of the magnesium are improved greatly by introducing the carbon fibers into the magnesium matrix through the EVI process. In the present study, the carbon short fiber reinforced magnesium matrix composites Csf/AZ91D were fabricated by EVI process. The microstructure and tensile property of Csf/AZ91D composites were investigated. The results showed that the microstructure of the composite presented a uniform distribution of carbon short fibers in the matrix and good interfacial integrity. The yield strength and stiffness of the composites increased with increasing carbon short fiber content, but at the cost of ductility. Nonetheless, Csf/AZ91D can keep relatively high ductility during the improvement of strength compared with reported composites in the literatures. Increasing carbon fiber content in the composite was not always beneficial to the ultimate tensile strength at the same magnitude. When the fiber content exceeds 10%, the matrix was not strengthened as greatly as under 10% fiber content. The yield strength improvement was attributed to (i) load-bearing effects due to the presence of carbon short fiber reinforcements; (ii) grain size refinement due to the large extrusion deformation; (iii) generation of dislocations to accommodate CTE mismatch between the matrix and the particles.

Effect of Processing Factors on Flexural Properties of Cf-HA/PMMA Composites

Short carbon fiber (Cf) reinforced nano-hydroxyapatite (HA)/poly(methyl methacrylate) (PMMA) matrix bio-composites were prepared by an in situ processing and solution co-mixing process. The influence of carbon fiber content, initiator dosage, and nano-HA mass fraction on the flexural properties of the composites were particularly investigated. The flexural strength and modulus were tested by universal testing machine. The flexural fracture surface morphologies were characterized using scanning electron microscope. Results reveal that the as-prepared Cf/HA-PMMA composites have excellent flexural properties. With the increase of carbon fiber content, benzoyl peroxide (BPO) dosage, HA mass fraction and reaction temperature, the flexural strength, and modulus of Cf-HA/PMMA composites first increase to a maximum and then decrease. The flexural strength and flexural modulus will reach the maximum value of 129.56 MPa and 4.47 GPa when carbon fiber mass content, BPO dosage, and HA mass content arrive at 4, 1.6, and 8 wt%, respectively and reaction temperature is 80°C.

Development and high stress abrasive wear behavior of milled carbon fiber‐reinforced epoxy gradient composites

AbstractMilled carbon fiber‐reinforced polysulfide‐modified epoxy gradient composites have been developed. Density and hardness increases with the increase of carbon fiber content in the direction of centrifugal force, which shows the formation of gradient structure in the composite. High stress abrasive wear test was conducted on the gradient composites by using a Suga Abrasion Wear Tester. Abrasive wear rate reduced on increase of milled carbon fiber content from 0.15 to 1.66 vol%. Reduction in abrasive wear rate in milled carbon fiber‐reinforced epoxy gradient composites has been attributed to the increase of hardness, presence of random milled fibers, and debris of composite materials, which gave resistance and reduced wear rate. There is a small decrease in specific wear rate on adding 0.15 vol% milled carbon fibers. Further decrease of specific wear rate is observed on adding 0.45 vol% milled carbon fibers. After 3 N load, there is a decrease in specific wear rate behavior on adding 0.45 vol% carbon fibers, which further decreases on adding 0.60 vol% of carbon fibers. There is a remarkable decrease in specific wear rate up to 5 N load for 1.66 vol% milled carbon fiber‐reinforced composite. Reduction in specific wear rate on adding milled carbon fibers is based on the formation of debris, which remained intact in their respective positions due to the interfacial adhesion between milled carbon fibers and epoxy resin. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Friction and wear mechanisms of PA66/PPS blend reinforced with carbon fiber

AbstractThe mechanical and tribological properties of carbon fiber (CF) reinforced polyamide 66 (PA66)/polyphenylene sulfide (PPS) blend composite were studied in this article. It was found that CF reinforcement greatly increases the mechanical properties of PA66/PPS blend. The friction coefficient of the sample decreases with the increase of CF content. When CF content is lower (below 30%), the wear resistance is deteriorated by the addition of CF. However, the loading of higher than 30% CF significantly improves the tribological properties of the blend. The lowest friction coefficient (0.31) and the wear volume (1.05 mm3) were obtained with the PA66/PPS blend containing 30% CF. The transfer film and the worn surface formed by sample during sliding were examined by scanning electron microscopy. The observations revealed that the friction coefficient of PA66/PPS/CF composite depends on the formation and development of a transfer film on the counterface. The abrasive wear caused by ruptured CFs (for lower CF content) and the load bearing ability of CFs (for higher CF content) are the major factors affecting the wear volume. In addition, the improvements of mechanical properties, thermal conductivity, and self‐lubrication of bulk CFs are also contributed to the wear behavior of PA66/PPS/CF composite. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Pultruded Hybrid Fibre (Glass/Carbon) Reinforced Unsaturated Polyester Composites: Mechanical and Thermal Properties

A feasibility study on the pultrusion of hybrid fibre (glass/carbon) reinforced unsaturated polyester composites has been conducted using a proprietary method. This was in order to obtain the best mechanical and thermal properties and the optimum price composites for pultrusion. The static mechanical properties (flexural strength, flexural modulus and notched Izod impact strength), dynamic mechanical properties (dynamic storage modulus, E' and dynamic loss tangent, tanδ) and thermal properties (weight loss by thermogravimetric analysis, TGA) of pultruded hybrid fibre reinforced unsaturated polyester composites were investigated because they are of great interest and importance in structural applications, and very sensitive to the processing conditions. Results show that the flexural modulus increased with increasing carbon fibre content. The flexural strength and notched Izod impact strength increased with decreasing carbon fibre content. The E' increased with increasing carbon fibre content, calcium carbonate content and postcure temperatures. The peak in the loss tangent was shifted to a higher temperature when the carbon fibre content was increased. From TGA, the weight loss of the pultruded composites increased with decreasing carbon fibre content in an inert (N2 gas) atmosphere. Furthermore, they increased with increasing carbon fibre content in an air atmosphere.

Influence of Carbon Fiber Additions on Friction Properties and Running‐In Behavior of Silicon Nitride‐Based Composites Under Water Lubrication

The friction behavior of Si3N4/carbon fiber composites under various sliding conditions and with various carbon fiber contents was researched. The carbon fiber content did not affect the friction coefficient under hydrodynamic‐type lubrication, but the running in distance decreased with increasing carbon fiber content. In a Stribeck analysis, the addition of carbon fibers to the Si3N4 material shifted the transition point from a hydrodynamic to mixed lubrication regime to more severe conditions, and had an effect on the friction coefficient under the boundary lubrication‐type regime.

Mechanical, electrical and thermal properties of carbon fiber reinforced poly(dimethylsiloxane)/polypyrrole composites

Abstract Conductive and flexible carbon fiber (CF) reinforced polydimethylsiloxane (PDMS)/polypyrrole (PPy) composites were synthesized electrochemically. Electrochemical synthesis was performed at +1.1 V using p -toluenesulfonic acid as supporting electrolyte and water as solvent. Composites were characterized by thermal gravimetric analysis, scanning electron microscopy (SEM), conductivity measurements and mechanical tests. Conductivities of composites were observed in the range of 2.2–4 S/cm. SEM studies show that CFs were coated by PDMS/PPy matrix uniformly. In mechanical tests, it has been observed that tensile strength of composites increased with increasing CF content. Higher percent elongation was achieved by the addition of PDMS. Highly flexible, foldable and mechanically strong conductive composites were obtained.

Mechanical behavior of carbon fiber reinforced polyamide composites

The purpose of this work is to compare tensile, compressive and interlaminar shear properties of different carbon reinforcement/polyamide composites obtained by interfacial polymerization and hot compression molding techniques. Two types of composite matrices were studied: polyamide 6 and polyamide 6/6, both reinforced by fabric and unidirectional carbon fibers. The effects of the fiber volume fraction and the matrix on mechanical properties were analyzed through tensile, interlaminar shear and compressive tests. In general, the results have shown a slight increase of the composite elastic modulus, tensile and compressive strength with the increase of carbon fiber content. The microscopic damage development within selected composites during the loading has been observed through optical and scanning electron microscope techniques and has shown that shear failure at the fiber/matrix interface has been mostly responsible for damage development, initiated at relatively low stress.

Quantitative evaluation of iPP nucleation in the presence of carbon fibres: Induction time approach

Crystallization and nucleation behavior in model composites based on iPP and differently sized carbon fibres have been analyzed in this work. The investigations were performed in the isothermal regime (120?127 ?C) using PLM and DSC. The results were analyzed by applying the Avrami and Muchova-Lednicky methods. It was shown that the carbon fibre surface acts as a nucleating agent during the crystallization of the iPP matrix. The highest effect was obtained with the fibres of PP-compatible size (C-T) related to unsized carbon fibres (C-U). The induction time, ti, and half-time of crystallization decreased with increasing carbon fibre content. The energy effect on the thickness of the critical nucleus decreased in the presence of C-fibres, a fact confirmed by a decrease in the nucleation parameter Q and the difference energy parameter ?? (Q decreased from ? 4.96 for iPP to ?21.32 for C/iPP model composites, and ?? decreased from 6.14x10-7 J/cm2 for iPP to 1.63x10-7 J/cm2 for model composites). The results of the model composites and their comparison with published data confirmed that the Muchova-Lednicky method could be successfully applied for the quantitative evaluation of the nucleation parameters not only in the temperature range previously suggested (130?138?C), but also at lower crystallization temperatures (Tc=121?127?C).

Electrochemical preparation and characterization of carbon fiber reinforced poly(dimethylsiloxane)/polythiophene composites: electrical, thermal and mechanical properties

A series of polydimethylsiloxane (PDMS)/polythiophene (Pth)/carbon fiber (CF) composites was synthesized by electrochemical polymerization using tetrabutylammoniumtetrafluoroborate (TBAFB) as supporting electrolyte and acetonitrile as solvent. Composites were characterized by TGA, SEM, and mechanical tests and conductivity measurements. Conductivities of composites were in the range of 2–5 S/cm. SEM studies show that CF were coated by PDMS/Pth matrix and well oriented in the matrix. In mechanical tests it has been observed that higher percent elongation was obtained by increasing PDMS content whereas tensile strength and modulus of composites increases with increasing CF content.

Determination of the type of charge carriers in carbon fiber/polymer composite

The Hall effect method has been used to determine the charge carriers' density in polycarbonate/carbon fibers composites. It was found that the measured Hall voltage varies almost linearly with Hall current. This behavior indicates that the majority of the charge carriers are of one type. The sign of the slope of this relation varies from positive to negative for composite specimens of about 18 wt% carbon fibers. This suggests that composites of low fiber content are functioning as p-type material and then change to n-type with increasing carbon fiber content. The observed anisotropic behavior of the charge carriers' density makes it difficult to calculate the kinetic parameters, such as the carriers mobility of such composite materials, from the Hall effect analysis.

Determination of the type of charge carriers in carbon fiber/polymer composite

The Hall effect method has been used to determine the charge carrier density in polycarbonate/carbon fibers composites. It was found that the measured Hall voltage varies almost linearly with Hall current. This behavior indicates that the majority of the charge carriers is of one type. The sign of the slope of this relation varies from positive to negative for composite specimens of about 18 wt% carbon fibers. This suggests that a composite of low fiber content is functioning as p-type material and then changes to n-type with increasing carbon fiber content. The observed anisotropic behavior of the charge carrier density makes it difficult to calculate the kinetic parameters of the carrier mobility of such composite materials from the Hall effect analysis.

Recyclability of Waste Cord of Synthetic Fibers as Matrix Material for Thermoplastic Hybrid Composites

The hybrid composites were molded using the waste cord of synthetic fabrics as a matrix material, wherein continuous glass and carbon fibers were used for the reinforcements and were fed directly into the injection molding machine together with the waste cord. The measured tensile strength and tensile modulus of the molded composites were much higher than those of the matrix material, and they increase with increasing carbon fiber content. It is concluded that the molding system devised herein shows promise for contributing to the material recycling of waste cord of synthetic fabrics.

Crystallization Behavior of Carbon Fiber Reinforced Polyamides (I) Dynamic and Isothermal Crystallization

Abstract Polyamide (PA) was compounded with carbon fiber (CF) with various contents (0, 5, 15, 20 vol.-%) using an elastic extruder. The effect of both the carbon fiber contents and the compounding method on thermal behavior and characteristics of crystallization are studied using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and polarizing optical light microscopy (POL). Thermal investigation was carried out under programmed cooling and isothermal conditions. The following results were obtained: (1) The crystallization temperature became higher with the increase of carbon fiber content, while the melting temperature and enthalpy were scarcely affected by the carbon fiber content. (2) The compounding methods affected the thermal behavior of composite systems. The samples that have been extruded twice have higher crystallization and melting temperatures as well as higher melting enthalpy. (3) Isothermal crystallization was observed using DSC. From the rate constant k and Avrami's index n, it was found that crystallization was accelerated by the presence of carbon fiber without changing the type of nucleation. (4) The polarizing micrographs showed that the nucleation of PA occurred on the surface or close to the CF.