Incorporation of silicon dioxide nanoparticles at the carbon fiber‐epoxy matrix interphase and its effect on composite mechanical properties

Functionalized silicon dioxide nanoparticles (nano‐fSiO₂) were uniformly deposited on the surface of carbon fibers (CFs) using a coating process which consisted of immersing the fibers directly in a suspension of nano‐fSiO₂ particles and epoxy monomers in 1‐methyl‐2‐pyrrolidinone (NMP). The 0° flexural properties, 90° flexural properties, and Interlaminar shear strength (ILSS) mechanical properties of unidirectional epoxy composites made with nano‐fSiO₂+epoxy sized carbon fibers, with control fibers, and with epoxy‐only sized fibers were measured and compared. An obvious increase of the fiber/matrix adherence strength was obtained with the nano‐fSiO₂+epoxy coating. The nano‐fSiO₂+epoxy sized CF/epoxy composites showed a relative increase of 15%, 50%, and 22% in comparison to control fibers, for the Interlaminar shear strength, the 90^° flexural strength and the 90° flexural modulus, respectively, but little e difference was measured between the different systems for the 0° flexural properties. The observation of the fracture surfaces by scanning electron microscopy of composite fracture confirmed the improvement of the interfacially dependent mechanical properties. POLYM. COMPOS., 38:1474–1482, 2017. © 2015 Society of Plastics Engineers     

Mechanical properties of epoxies reinforced with chloride-treated aramid fibers

Surface treatment of aramid fibers by immersion in a solution of methacryloyl chloride in carbon tetrachloride was carried out, and the resulting material was examined by means of electron microscopy and chemical analysis in an attempt to record any changes in the morphology and nature of the surface. Mechanical testing of tensile, flexural, and interlaminar shear strength, as well as dynamic mechanical analysis (DMA), were performed in an attempt to explore the effect of this treatment on the strength of the fiber. In a subsequent stage, the performance of those fibers as reinforcement in composites of epoxy matrix was assessed. The aim of this study was to provide more information about the interactions between the chloride-treated aramid fibers and the epoxy resin and, more specifically, to compare the behavior of the epoxy matrix composites with those composed of unsaturated polyester, polyethylene, and polyurethane matrix, which were studied in the past. It was found that specimens containing chloride-treated aramids display better flexural properties, whereas their tensile strength is drastically reduced. Improved performance was also identified by the DMA experiments. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:–, 1997     

Static and dynamic mechanical properties of a kenaf fiber–wood flour/polypropylene hybrid composite

A natural fiber hybrid composite containing equal proportions of kenaf fibers (KFs) and wood flour (WF) as the reinforcements and polypropylene (PP) as the polymer matrix was prepared, and its static and dynamic mechanical properties were compared with KF/PP and WF/PP composites. Static tensile and flexural tests and dynamic mechanical analysis (DMA) were carried out. The hybrid composite exhibited tensile and flexural moduli and strength values closer to those of the KF composite, which indicated a higher reinforcing efficiency of KFs compared with WF. DMA revealed that although the glass‐transition temperature remained unchanged by the replacement of half of the WF by KFs, the α‐transition temperature of the hybrid composite was identical to that of WF composite. The magnitudes of both the α and β (glass) transitions of the hybrid composite were comparable to that of the WF/PP composite. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 665–672, 2005     

The influence of addition of carbon nanotube and graphene platelets on characteristics of carbon/basalt fiber reinforced intra-ply hybrid composites

In this study, effects of addition of carbon nanotubes (CNTs) and graphene platelets (GPLs) on characteristics of carbon/basalt fiber reinforced intra-ply hybrid composites were investigated. The composites were fabricated using vacuum assisted resin infusion molding (VARIM) method in two types including bare and 0.1, 0.5 wt.% of GPL and CNT nanoparticles filled hybrid composites. Fabricated normal and multiscale composites were cut by water jet and mechanical properties of specimens were examined by tensile, flexural, SBS experiments. Therefore, the modulus of elasticity, flexural modulus, tensile and flexural strength and ILSS of bare and multiscale composites were compared. Thermomechanical properties of fabricated composites were evaluated by dynamic mechanic analyze (DMA), thermogravimetric analyze ( TGA) and thermal conductivity (TC) tests and storage modulus, loss modulus, damping ratio, glass transition temperature, weight loss and derivative weight loss were compared in fabricated normal and multiscale composites. Similarly, modal properties of fabricated composites such as natural frequency and damping factor were obtained by vibrational tests and compared in fabricated composites. According to the results, the addition of carbon-based nanoparticles improved the characteristics of carbon/basalt fiber intra-ply hybrid composites. The response of composites was directly proportional to the addition ratio of the carbon-based nanoparticles.     

Synthesis of hybrid ZnO/CNTs nanoparticles and their reinforcement in nylon‐6 polymer fibers

In this investigation, in situ synthesis of zinc oxide nanoparticles in the presence of multiwalled carbon nanotubes (CNTs) have been carried out using a sonochemical technique. Zinc(II)acetate was used as a source of ZnO in the presence of ethylene glycol (EG) to obtain zinc oxide (ZnO) nanoparticles. The synthesized hybrid ZnO/CNTs nanoparticles were used as reinforcements to enhance the mechanical, thermal and UV absorbing properties of Nylon‐6 composite fibers. The polymer nanocomposites (PNC) were fabricated by dry mixing Nylon‐6 polymer powder with the ZnO/CNTs hybrid nanoparticles as the first step, then followed by the drying and melt extrusion process of fiber materials in a single‐screw extruder. The extruded fibers were stretched and stabilized using a godet set‐up and wound on a Wayne filament winder machine. The hybrid ZnO/CNTs infused Nylon‐6 composite fibers were compared with commercial ZnO, CNTs infused Nylon‐6 composite fibers and neat Nylon‐6 fibers for their structural and thermal properties. The morphological characteristics of ZnO/CNTs nanoparticles were carried out using X‐ray diffraction and transmission electron microscopy (TEM) techniques. The Nylon‐6 PNC fibers which were of ～80 μ size were tested mechanically. The tensile tests revealed that failure stress of the 1% infused ZnO/CNTs Nylon‐6 PNC fibers is about 73% higher than the neat extruded Nylon‐6 fiber and the improvement in the tensile modulus is 377.4%. The DSC results show an increase in the glass transition temperature and crystallization for ZnO/CNTs infused Nylon‐6 PNC fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Thermal and mechanical properties of hybrid carbon/oxidized polyacrylonitrile fibers‐epoxy composites

Nowadays, hybrid composites are one of the important materials in industry due to their special properties. In this research, hybrid oxidized polyacrylonitrile (PAN) and carbon fibers reinforcement were used in epoxy matrix. The hybrid composites were fabricated using the hand lay‐up technique by placing the reinforcements in different layering sequences. Thermal and mechanical properties of these hybrid composites were investigated by thermal analysis, horizontal burning, tensile and bending tests. The tensile test results indicated that increasing oxidized polyacrylonitrile fibers (OPFs) to carbon fibers ratio decreased tensile strength and elastic modulus but increased failure strain. Hybrid oxidized PAN and carbon fibers reinforcement in composites led to decreasing flexural stress and modulus, and increasing flame retardancy. Thermal analysis results also showed that the maximum rate of mass loss in all composites was 370.6°C. It was also found that the maximum and minimum amounts of char residue at 900°C were related to the composites with four layers of carbon and OPFs, respectively. POLYM. COMPOS., 38:1412–1417, 2017. © 2015 Society of Plastics Engineers     

Short term flexural creep behavior of wood-fiber/polypropylene composites

Short term flexural creep tests were conducted to investigate the creep behavior of wood-fiber polypropylene composites. Three experimental parameters were selected: the addition of a wetting agent, temperature, and wood-fiber concentration. All creep curves are presented in terms of relative creep as a percentage of instantaneous (initial) strain. The creep power law model was used to accurately fit the creep data. The addition of a wetting agent greatly reduced the creep at high stress, but had little effect at a lower stress level. The extent of relative creep increased with increasing temperature. It was found that the slope of the power law model was directly proportional to the temperature. The addition of wood-fibers into pure polymer greatly improved the creep resistance of the matrix polymer. The relative creep of the composites decreased with an increase in wood-fiber concentration. However, the composite showed relatively large creep compared with that of solid wood. It was found that both the time exponent and slope of the power law model were inversely related to wood-fiber concentration. The flexural modulus of the composites also had an inverse relationship with the time exponent.     

Effect of fiber chemical treatment of nonwoven coconut fiber/epoxy composites adhesion obtained by RTM process

In this work untreated and alkali treated nonwoven coconut fiber mats/epoxy resin composites were manufactured using the resin transfer molding process. The alkaline solution removes some impurities present on fibers superficial layers and the effect regarding fiber/matrix adhesion were investigated by thermogravimetric analysis, dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), ultrasonic C‐scan, and quasi‐static flexural test. Results show a removing of some amorphous fibers constituents, mainly waxes, extractives, and hemicellulose, revealing the fiber roughness surface but no initial degradation temperature changing. Regarding the composites, a similar interfacial adhesion was observed in both one through the results of SEM, DMA and quasi‐static flexural tests. The conclusion is that chemical treatment conditions applied on the fiber surface was been suitable to improve fiber roughness but did not the adhesion between coconut fibers mat and epoxy resin. POLYM. COMPOS., 38:2518–2527, 2017. © 2015 Society of Plastics Engineers     

Creep behavior of biocomposites based on sisal fiber reinforced cellulose derivatives/starch blends

Biodegradable composites based on cellulose derivatives/starch blends reinforced with sisal short fibers were fabricated by injection molding. Results of short-term flexural creep tests are reported to investigate the time-dependence behavior of the composites. Fiber content and temperature effects are also considered, taking into account various methods and equations. At short times, a creep power law is employed. A master curve with the Arrhenius model is used to determine the creep resistance at longer times and different temperatures. Good fitting of the experimental results with the four-parameter model is reported, leading to a relationship between the observed creep behavior and the composite morphology. The addition of sisal fibers to the polymeric matrix promotes a significant improvement of the composite creep resistance. Polym. Compos. 25:280–288, 2004. © 2004 Society of Plastics Engineers.     

Effect of Fiber Acid Treatment on the Dynamic Mechanical Properties of Unsaturated Polyester/Carbon Fiber Unidirectional Composites

In this study, the surface modification of carbon fiber by sulfuric acid is investigated. Atomic Force Microscopy was employed to capture the corresponding changes in the surface roughness of the carbon fiber. Moreover, using treated and untreated fibers, unsaturated polyester unidirectional composite rods were prepared and their flexural properties were determined by three-point bending and dynamic mechanical thermal analysis.

The results indicated that the carbon fiber surface roughness increases in all samples. It is also found that treating the fiber decreases the magnitude of loss modulus. Besides, the flexural strength of composites made of the treated carbon fiber significantly increased.     

A comparative study on the influence of epoxy sizings on the mechanical performance of woven carbon fiber-epoxy composites

In the present work the effect of epoxy sizings on the fracture behavior of woven carbon fiber tetrafunctional epoxy composites has been investigated. Three-point flexural, short beam shear (SBS) and Mode-II interlaminar fracture toughness (ENF) tests have been carried out. Wettability and Atomic Force Microscopy (AFM) studies have been performed on commercial sized, desized and 0.7 wt% TGDDM and 0.7 wt% DGEBA sized carbon fibers. Dynamic mechanical thermal analysis and Scanning Electron Microscopy (SEM) studies were also carried out on the different carbon fiber/epoxy composites. The used sizing treatments provided composites with improved mechanical properties due to the enhancement achieved in the fiber-matrix adhesion. Polym. Compos. 25:319–330, 2004. © 2004 Society of Plastics Engineers.     

Electromagnetic interference properties of carbon nanofiber–reinforced acrylonitrile–styrene–acrylate/natural graphite composites

Acrylonitrile–styrene–acrylate/natural graphite/carbon nanofiber composites (ASA/NG/CNF) were prepared using a melting blending method. The effects of CNFs on the morphology, rheological properties, dynamical mechanical properties, electrical resistivity, and electromagnetic interference shielding effectiveness (EMI SE) were studied using a scanning electron microscope, a rotational rheometer, and dynamic mechanical analysis (DMA). The addition of CNFs changed the oriented and laminated structure of the ASA/NG composite. The flexural strength of the ASA composite reached a maximum at 6% CNF, and then it began to decrease. The addition of CNFs did not alter the glass‐transition temperature of ASA, but it largely increased the storage modulus of the composite in DMA tests. In the rheological measurements, the complex viscosity and storage modulus of the composite increased as CNF content increased, and the resistance to creep of the composites was significantly increased by the addition of CNFs. The electrical resistivity of the ASA composites decreased from 49.8 Ω cm to 2.3 Ω cm as the CNF content was increased from 0 to 12%. At the same time, the EMI properties of the composites rose from 15 dB to 30 dB in the frequency range 30–1500 MHz. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45455.     

Electrospun nano‐scaled glass fiber reinforcement of bis‐GMA/TEGDMA dental composites

The objective of this study was to investigate the electrospun nano‐scaled glass fiber reinforcement of 2,2′‐bis[4‐(methacryloxypropoxy)‐phenyl]‐propane/triethylene glycol dimethacrylate (Bis‐GMA/TEGDMA) dental composites. The hypothesis was that incorporation of the surface‐silanized electrospun nano‐scaled glass fibers into Bis‐GMA/TEGDMA dental composites would result in substantial improvement on mechanical properties. To test the hypothesis, photo‐cured Bis‐GMA/TEGDMA dental composites filled with various mass fractions of surface‐silanized electrospun nano‐scaled glass fibers were systematically fabricated; and their mechanical properties were then evaluated. The results indicated that small mass fraction substitutions (1, 2.5, 5, and 7.5%) of conventional dental filler with the surface‐silanized electrospun nano‐scaled glass fibers, significantly improved the flexural strength, elastic modulus, and work of fracture values of 70% (mass fraction) filled composites, by as much as 44%, 29%, and 66%, respectively. The mechanical properties of the composites could be further improved by optimizing the chemical compositions and the surface treatment methods of the fibers. We envision that the electrospun nano‐scaled glass fibers could be utilized to develop the next generation dental composites, which would be particularly useful for large posterior restorations. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Fabrication and properties of nano‐ZnO/glass‐fiber‐reinforced polypropylene composites

Polypropylene (PP) is widely used in many fields, such as automobiles, medical devices, office equipment, pipe, and architecture. However, its high brittle transformation temperature, low mechanical strength, dyeing properties, antistatic properties, and poor impact resistance, considerably limit its further applications. Nano‐ZnO treated by KH550 coupling agent and glass fibers (GFs) were introduced in order to improve the mechanical performance and flowability of PP in this research. The crystallization behavior and microstructure of nano‐ZnO/GFs/PP hybrid composites were analyzed by differential scanning calorimetry, transmission electron microscopy, and scanning electron microscopy. The effect of crystallization behavior on the mechanical properties of the nanocomposites was investigated and analyzed. The results indicated that nano‐ZnO surface‐coupled by KH550 could be uniformly dispersed in the PP matrix. The incorporation of nano‐ZnO and GFs resulted in increases of the crystallization temperature and crystallization rate of PP and a decrease of the crystallization degree. The introduction of nano‐ZnO and GFs also enhanced the tensile strength and impact toughness of the hybrid composites and improved their fluidity. Composites containing 2% of nano‐ZnO and 40% of GFs possessed the optimum mechanical properties. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Effect of plasma modification on the mechanical properties of carbon fiber/phenolphthalein polyaryletherketone composites

A study was carried out to investigate the effect of plasma modification on the mechanical properties of carbon fiber/phenolphthalein polyaryletherketone composites. The influence of oxygen plasma treatment on the surface properties of carbon fibers was investigated by X‐ray photoelectron spectroscopy and atomic force microscopy. The results indicated that oxygen plasma treatment was capable of increasing the concentrations of the oxygen‐containing groups of the carbon fiber surface as well as enhancing surface roughness. Both the chemical bonding and mechanical interlocking gave rise to an increase of the interlaminar shear strength of composite. Scanning electron microscope photographs showed that the destruction mode of composites was changed after the carbon fibers were treated by oxygen plasma. The results also indicated that the flexural properties of plasma‐treated carbon fiber composites were improved. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

Creep behavior of nylon-6 thermoplastic composites

A systematic investigation of the creep behavior of nylon-6 thermoplastic composites reinforced with continuous carbon fibers was conducted by a strain gauge method. The creep strains of carbon fiber/nylon-6 composites were measured at various stress conditions and temperatures. The relationship between the creep strain, strain rate, creep compliance and stress condition, time, and temperature were established. The experimental creep strain data were shifted to a reference temperature to form a master curve by using the time-temperature superposition principle. The master curve can be used to predict the creep behavior of the carbon fiber/nylon-6 composites over long times. The effect of fiber orientation on the creep behavior was also measured and reported.     

Effect of short carbon fiber content on the mechanical properties of TiB2-based composites prepared by spark plasma sintering

In this study, TiB₂-30 vol% SiC composites containing 0, 5, 10, and 15 vol% short carbon fibers (C_f) were produced by spark plasma sintering (SPS). The effect of carbon fiber content on microstructure, density, and mechanical properties (micro-hardness and flexural strength) of the fabricated composites was studied. Scanning electron microscopy (SEM) results indicated that the fibers were uniformly dispersed in the TiB₂–SiC matrix using wet ball milling before SPS process. Fully dense TiB₂–SiC–C_f composites were achieved by SPS process at 1900°C for 10 min under 30 MPa. With the addition of fibers, the relative density of the composites did not change considerably. Mechanical tests revealed that microhardness was reduced about 19% by the incorporation of carbon fibers, whereas the flexural strength improved significantly. However, the flexural strength diminished by adding carbon fibers above to critical value (5 vol%) due to residual thermal stresses, nonhomogeneous structure and graphitization of carbon fibers. It was found that the composite with 5 vol% C_f had the highest flexural strength (482 MPa), which was enhanced by 20% compared with the TiB₂–SiC composite.     

Improving delamination resistance of carbon fiber reinforced polymeric composite by interface engineering using carbonaceous nanofillers through electrophoretic deposition: An assessment at different in-service temperatures

In this article, modification of carbon fiber surface by carbon based nanofillers (multi-walled carbon nanotubes [CNT], carbon nanofibers, and multi-layered graphene) has been achieved by electrophoretic deposition technique to improve its interfacial bonding with epoxy matrix, with a target to improve the mechanical performance of carbon fiber reinforced polymer composites. Flexural and short beam shear properties of the composites were studied at extreme temperature conditions; in-situ cryo, room and elevated temperature (−196, 30, and 120°C respectively). Laminate reinforced with CNT grafted carbon fibers exhibited highest delamination resistance with maximum improvement in flexural strength as well as in inter-laminar shear strength (ILSS) among all the carbon fiber reinforced epoxy (CE) composites at all in-situ temperatures. CNT modified CE composite showed increment of 9% in flexural strength and 17.43% in ILSS when compared to that of unmodified CE composite at room temperature (30°C). Thermomechanical properties were investigated using dynamic mechanical analysis. Fractography was also carried out to study different modes of failure of the composites.     

Portland cement paste with aligned carbon fibers exhibiting exceptionally high flexural strength (> 100 MPa)

Here, we introduce a nozzle injection technique for carbon fiber-reinforced cement paste leading to unidirectional alignment of cement-embedded short carbon fibers that follow the movement direction of the guided nozzle. In comparison to non-reinforced cement pastes, this novel material exhibits a tremendous increase of its flexural strength upon admixing and aligning 1 to 3 percent (by volume) of chopped carbon fibers. Cement pastes containing carbon fibers aligned in the stress direction thus acquire high compressive and flexural strength values at the same time. Mechanical tests prove the material to withstand flexural loads larger than 100 MPa in conjunction with a deflection hardening behavior resembling that of high performance fiber-reinforced cementious composites at relatively low fiber volume content. Insights into the preparation, fiber alignment, rheology and the fracture behavior of this material are presented in this study.     

Fabrication of 2D C/C-SiC composites using PIP based hybrid process and investigation of mechanical properties degradation under cyclic heating

2D C/C-SiC composites were fabricated using PIP process by repeated impregnations of porous C/C composite preforms with polycarbosilane followed by pyrolysis. Effect of cyclic heating on flexural and shear strength of these composites was studied by exposing the test specimens to oxyacetylene flame for 20 s and cooling by a blast of air. The cyclic heating tests were repeated up to five times. Average flexural and shear strength of the as fabricated composites were about 330 MPa and 14.5 MPa respectively. After five heating and cooling cycles, average flexural and shear strength were reduced to 120 MPa and 5.5 MPa respectively. SEM, XRD, EDAX and XPS studies were also carried out to investigate the causes of strength reduction. Oxidation started preferentially at carbon matrix through the cut ends of the weft fibers. Oxidative damage due to repeatedly heating cooling was found to be much smaller in through-thickness direction due to passive oxidation of SiC matrix while severe damage was observed parallel to the fabric layers.