Mechanical Properties Of Carbon Research Articles

Tuning of Elastic Properties of Nanotubes by Imposing a Transverse Electric Field: Computational Approach

In this study, we investigated the influence of a transverse electric field on the mechanical properties of carbon, boron nitride, and silicon carbide nanotubes based on density functional theory and continuum mechanics. To evaluate the Young’s modulus of the nanotubes, a compressive distribution loading was implemented in the direction perpendicular to the longitudinal axis of the nanotubes in the presence and absence of an electric field. According to the obtained results from the geometry of the deformed nanotubes, an elliptical function was used to estimate the overall deformation. Based on the Green strain theory, the displacement of each particle is defined by the conversion matrix to transform the initial circular shape of the nanotubes to the final elliptical shape. The classical continuum theory was employed to estimate the relationship between strain energy and strain field of the nanotubes. An evolutionary genetic algorithm was used to achieve an accurate estimation of the fitting of the energy function versus strain based on the elasticity theory. In addition, the effect of the electric field on the electronic and mechanical properties of the nanotubes was investigated. The numerical results revealed that the nanotubes exposed to the electric field have more effective stiffness in comparison to the similar case in the off-field condition.

Effect of different amino functionalized carbon nanotubes on curing behavior and mechanical properties of carbon fiber/epoxy composites

Epoxy‐amine system is a type of important matrix material for preparation of carbon fiber composites. The amidation of carbon nanotubes (CNTs) has been widely developed for enhancing the mechanical properties of the epoxy resin matrix. However, the various amino‐functionalized CNTs will produce different effect in the same epoxy matrix due to the diversity in reactivity, compatibility, and dispersion stability. In this paper, the amino‐functionalized multiwalled carbon nanotubes (MWCNTs‐NH2) were prepared through surface grafting ethylenediamine and diethyltoluenediamine (DETDA; designated as MWCNTs‐EDA and MWCNTs‐DETDA), and dispersed into epoxy resin matrix in which the DETDA was also used as curing agent. Compared with MWCNTs‐EDA, the MWCNTs‐DETDA showed a better dispersion state and stability in the epoxy resin, and had a relatively small impact on the curing behavior of epoxy matrix. After adding 0.5 wt% MWCNTs‐DETDA, the unidirectional T700 carbon fiber composites exhibited the significantly enhanced interlaminar shear strength and flexural properties due to the uniform dispersion of MWCNTs‐DETDA and the modified interface bonding. The results indicated that the chemical compatibility between MWCNTs‐NH2 and resin matrix can exert an important influence on the microstructure, curing behavior, thermo‐mechanical properties, and mechanical properties of the epoxy resin and the resulting carbon fiber composites. POLYM. COMPOS., 39:E733–E744, 2018. © 2016 Society of Plastics Engineers

The relationship between microstructure and mechanical properties of carbon nanotubes/polylactic acid nanocomposites prepared by twin-screw extrusion

Twin-screw extrusion was applied to prepare the carbon nanotubes/polylactic acid (CNT/PLA) nanocomposites. Five different extruded plates were produced under variation of CNT concentrations. The internal microstructures were also observed by optical microscope to examine the distribution and dispersion of CNT in the PLA. Besides, the crystallinity of the CNT/PLA nanocomposites was investigated by differential scanning calorimetry (DSC) and density method. The effects of the CNT concentrations on the mechanical and electrical properties of the nanocomposites were investigated. Scanning electron microscope (SEM) was performed to observe the CNT dispersion in the nano-scale. These results suggested that the crystallinity was increased with the increase of CNT concentrations, demonstrating that CNT played a role as a nucleating agent in PLA. Moreover, the mechanical and electrical properties of PLA have been improved by a proper incorporation of CNTs due to a good distribution and dispersion of the CNTs.

A comparative study of the crystalline structure and mechanical properties of carbon fiber/polyamide 6 composites enhanced with/without silane treatment

The silane-treated carbon fiber induced the formation of transcrystalline structure and enhanced the interfacial adhesion between the fiber and polyamide 6 matrix.

A comparative study on the mechanical properties of carbon and glass fibre-reinforced epoxy, polyester and vinyl ester-based composites

In this paper, the effects of reinforcing and matrix material on the mechanical properties of composites were investigated. Carbon fibre (CF) and glass fibre (GF) are the most useful reinforcement materials in polymer-based composites, their major use being the manufacture of components in the aerospace, automotive and leisure industries. In this study, epoxy, polyester and vinyl ester-based matrix materials reinforced by CFs and GFs were manufactured by hand lay-up method. Mechanical properties were investigated by tensile and flexural testing methods. Composites with polyester-based and CF-reinforced composites exhibited the highest mechanical properties, whereas the epoxy-based and GF-reinforced composites showed lower mechanical properties.

Study of Quality of Carbon Fabric Reinforced Composite

The structure and mechanical properties of carbon fabric reinforced composites are studied. The quality of the produced composites is evaluated. The obtained data show how their quality can be improved.

Effects of bonding types of carbon fibers with branched polyethyleneimine on the interfacial microstructure and mechanical properties of carbon fiber/epoxy resin composites

Abstract A novel supercritical method for deposition of polyethyleneimine (PEI) onto carbon fibers (CFs) surface was reported. The surface functional groups, morphology, wettability and interphase properties of CFs grafted with PEI (CF-g-PEI) were studied, and compared to physically-adsorbed and chemically-adsorbed ones (CF-c-PEI and CF-ad-PEI). The CF-g-PEI exhibited the highest deposition amount and interfacial adhesion strength. Interface enhancement mechanism and failure mode have also been explored in details. However, impact resistance and single fiber tensile strength of CF-g-PEI were not optimal. Hence, based on different applications, a property balance of the resulting composite should be considered.

Optimization of interfacial microstructure and mechanical properties of carbon fiber/epoxy composites via carbon nanotube sizing

Repetitious sizing treatment was used to modify the carbon fiber (CF) surface with carbon nanotubes (CNTs) for improving interfacial properties of CF/epoxy composites. Interlaminar shear and flexural results showed that mechanical properties of composites were significantly depended on the dispersion state and contents of CNTs in interfacial regions. Increases of 13.45% in interlaminar shear strength and 20.31% in flexural strength were achieved in quintuple sized-CF/epoxy composites, whereas excessive CNTs led to decrease of interfacial performance due to defects induced by agglomerated CNTs. Energy dispersive X-ray spectroscopy and force modulation atomic force microscope were used to detect the structure of interfacial phase and results indicated that gradient interfacial structure with various thicknesses was formed due to CNT incorporation. This means that such a simple and efficient method to improve interfacial performance of composites via regulating the fiber–matrix interphase structure was developed and showed great commercial application potential.

Effect of processing conditions on the dispersion, electrical, and mechanical properties of carbon nanotube/polypropylene nanocomposites

Carbon nanotube (CNT)/polypropylene nanocomposites with different levels of CNT dispersion were created by melt mixing in order to reveal the influence of nanofiller state of dispersion on the nanocomposites electrical and mechanical properties. Optical microscopy and transmission electron microscopy were used to analyze the microstructure of the nanocomposite. Melt mixing energy, melt viscosity, and shear stress were analyzed to understand the influence of processing conditions on the microstructure and electrical properties. CNT dispersion in the polypropylene matrix was enhanced by increasing the melt mixing time and/or rotation speed. The electrical conductivity was found to be very sensitive to the changes in the CNT level of dispersion, while the tensile strength and secant modulus did not show any significant response to the enhancement in the nanofiller state of dispersion.

A comparative study on mechanical properties of carbon fiber/PEEK composites

The aim of this work was to improve mechanical properties such as flexural strength and interlaminar shear strength (ILSS) of polyetheretherketone (PEEK) thermoplastic polymer which has very high processing temperature due to its high melting temperature. Carbon fiber (CF) surface was modified by two different methods: oxidative and non-oxidative. Piranha solution and chromate solution were used for chemical treatment (oxidative treatment), and silicone based polymers were used for polymer coating (non-oxidative). The changes on the surface structure and surface chemistry were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy (FTIR), respectively. FTIR results indicate that coating fibers decreases carbon element content, whereas increases the oxygen and silicone content as well as their functional groups on the surface. Flexural strength and ILSS properties of CF/PEEK composites were measured according to ASTM D-790 and ASTM D2344, respectively.

125 CFRTPの機械的特性に及ぼす熱可塑性エポキシ樹脂の分子量の影響

125 CFRTPの機械的特性に及ぼす熱可塑性エポキシ樹脂の分子量の影響

Effect of Plasma Etched CNFs on Toughness and Mechanical Properties of Epoxy Composites

Carbon nanofibers (CNFs) are plasma etched by using cold plasma of air and helium for different time durations. Changes in surface functional groups of CNFs due to plasma treatment were estimated by using elemental analysis and temperature programmed decomposition in helium atmosphere. The influence of plasma etched CNFs on the toughness of epoxy and tensile and flexural strength of carbon–epoxy composites have been studied. Results indicate that, air plasma etched CNFs can improve the toughness of epoxy, while helium plasma etched CNFs could not impart improved toughness to epoxy composites. On the other hand, mechanical properties of carbon–epoxy made with air plasma etched CNFs improved significantly as compared to helium plasma etched CNFs as well as untreated CNFs.

Temperature effect on the mechanical properties of carbon, glass and carbon–glass FRP laminates

Externally bonded fiber reinforced polymer (FRP) laminates are widely used to strengthen and rehabilitate reinforced concrete (RC) structural members in flexure and shear. Despite the clear and proven advantages of using FRPs over traditional materials, the greatest disadvantage to its wide utilization is the limitation in knowledge of the behavior of such composite materials after being exposed to high temperatures. The aim of this paper is to experimentally investigate the variation of mechanical properties in terms of the elastic modulus and tensile strength of composite carbon (C), composite glass (G) sheets and their hybrid combinations (CG) when exposed to different temperatures, ranging from 25°C to 300°C. All specimens were subjected to the specified temperature level for 45min and left to cool down for 24h prior to testing. Stress–strain relationships were plotted and the different observed failure modes were discussed. Based on the test results, the decrease in the mechanical properties of the composite C and G sheets was more severe than those of the composite hybrid CG sheets. In particular, the elastic modulus of the C, G and CG at 250°C was reduced by about 28%, 26% and 9%, respectively and their tensile strength at the same temperature was reduced by about 42%, 31% and 35%, respectively, all as compared to room temperature values. Tested specimens failed in brittle rupture of fiber for low range of temperatures (100–150°C) and by partial loss of epoxy adhesives followed by sheet splitting for high range of temperatures (200–250°C). The calculated values of the mechanical properties of C, G and CG at elevated temperatures can be used as valuable input in computer modeling of RC members strengthened with externally bonded FRP laminates and subjected to elevated temperatures.

Effects of electron irradiation in space environment on thermal and mechanical properties of carbon fiber/bismaleimide composite

The effects of electron irradiation in simulated space environment on thermal and mechanical properties of high performance carbon fiber/bismaleimide composites were investigated. The dynamic mechanical properties of the composites exposed to different fluences of electron irradiation were evaluated by Dynamic mechanical analysis (DMA). Thermogravimetric analysis was applied to investigate the changes in thermal stability of the resin matrix after exposure to electron irradiation. The changes in mechanical properties of the composites were evaluated by flexural strength and interlaminar shear strength (ILSS). The results indicated that electron irradiation in high vacuum had an impact on thermal and mechanical properties of CF/BMI composites, which depends on irradiation fluence. At lower irradiation fluences less than 5×1015cm−2, the dynamic storage modulus, cross-linking degree, thermal stability and mechanical properties that were determined by a competing effect between chain scission and cross-linking process, decreased firstly and then increased. While at higher fluences beyond 5×1015cm−2, the chain scission process was dominant and thus led to the degradation in thermal and mechanical properties of the composites.

Thermal and mechanical properties of carbon nanotube/epoxy nanocomposites reinforced with pristine and functionalized multiwalled carbon nanotubes

In this study, the effects of functionalization and weight fraction of mutliwalled carbon nanotubes (CNTs) were investigated on mechanical and thermomechanical properties of CNT/Epoxy composite. Epoxy resin was used as matrix material with pristine‐, COOH‐, and NH2‐functionalized CNTs as reinforcements in weight fractions of 0.1, 0.5, and 1.0%. Varying (increasing) the weight fraction and changing type (pristine or functionalized) of CNTs caused increment in Young's modulus and tensile strength as observed during mechanical tests. CNT reinforcement improved thermal stability of the nanocomposites as observed by thermogravimetric analysis. Thermomechanical analysis showed a slight reduction in free volume of the polymer, that is a drop in coefficient of thermal expansion, prior to glass transition temperature (Tg) beside a slight increase in Tg value. Dynamic mechanical analysis indicated an increase in storage modulus and Tg owing to the strength addition of CNT to the matrix alongside the hardener. Scanning electron microscopy analysis of the fractured surface(s) revealed that CNTs were well dispersed with no agglomeration and resulted in reinforcing the matrix. POLYM. COMPOS., 36:1891–1898, 2015. © 2014 Society of Plastics Engineers

Electrical and mechanical properties of carbon nanofiber/graphene oxide hybrid papers

Abstract Carbon nanofiber (CNF)/graphene oxide (GO) hybrid papers are prepared by vacuum filtration of mixed dispersion with varied CNF to GO weight ratios. The effects of GO content, precursor GO size and reduction on the structure, electrical conductivity and mechanical properties of hybrid papers are studied. The electrical conductivity of hybrid papers shows a decreasing trend before reduction, while it drastically increases after reduction with increasing GO content, a testament to the dominant role played by GO sheets. The tensile strength and Young’s modulus of hybrid papers exhibit similar performance with respect to GO content, confirming the importance of GO sheets. The GO sheet size has a positive effect on mechanical properties of hybrid papers through better alignment and their role as the substrate.

Mechanical properties of carbon fiber/cellulose composite papers modified by hot-melting fibers

Carbon fiber (CF)/cellulose (CLS) composite papers were prepared by papermaking techniques and hot-melting fibers were used for modification. The mechanical properties of the obtained composite papers with different CF, CLS and hot-melting fiber ratios were studied and further discussed. It is observed that, for both CF/CLS composite papers and those modified by hot-melting fibers, the normal stress firstly increases and then declines with the addition of carbon fibers. The results also show that with the addition of hot-melting fibers, the modified papers exhibit enhanced mechanical performance compared to CF/CLS composite papers. Through SEM characterization, it is confirmed that the improvement of mechanical properties attributes to the reinforcement of adhesive binding at the fiber overlap nodes. Also, through four-probe method, the resistivity and the electrical performance of the modified and unmodified papers were characterized and the result shows that the hot-melting fiber modification brings no harm to the electrical properties.

Effect of Novolac Resin and Modified Novolac Resin on Mechanical Properties of Carbon Fiber/Epoxy Composites

ABSTRACTThe effects of novolac resin (NR) and modified novolac resin (MNR) on the stiffness and toughness of the carbon fiber (CF)/epoxy composites were studied when using these two kinds of modifiers with different physical and chemical performance. The results show that both NR and MNR are excellent toughening agents for the CF/epoxy composites, and the composites treated with MNR present better toughness than that of NR. However, the stiffness of the composites is almost unchanged when adding MNR. The mechanisms were analyzed by fracture studies using scanning electron microscopy and the decrease of cross‐link density caused by MNR was deduced to the toughening effects.

The effect of needleless electrospun nanofibrous interleaves on mechanical properties of carbon fabrics/epoxy laminates

The effect of polyacrylonitrile nanofibrous interlaminar layers on the impact properties of unidirectional and woven carbon fabric (CF)-reinforced epoxy (EP) matrix composites was investigated. The nanofibers were produced directly on the surface of carbon fabrics by a needleless electrospinning method, and composites were then prepared by vacuum-assisted impregnation. Interlaminar shear stress tests, three-point bending, Charpy-impact and instrumented falling weight tests were carried out. The fracture surfaces were analyzed by scanning electron microscopy. Due to the nano-sized reinforcements, the interlaminar shear strength of the woven and unidirectional fiber-reinforced composites was enhanced by 7 and 11%, respectively. In the case of the falling weight impact tests carried out on woven reinforced composites, the nanofibers increased the absorbed energy to maximum force by 64% compared to that measured for the neat composite. The Charpy impact tests indicated that the nanofiber interleaves also led to a significant increase in the initiation and total break energies. Based on the results, it can be concluded that the presence of nanofibers can effectively increase the impact properties of composites without compromising their in-plane properties because the thickness of the composites was not altered by the presence of interleaves. The improvement of the impact properties can be explained by the good load distri- bution behavior of the nanofibers.

Kinetic Study of Resin-Curing on Carbon Fiber/Epoxy Resin Composites by Microwave Irradiation

Microwave processing has great potential for improving composite manufacturing such as reduction of curing time, energy requirements and operational costs. In this paper, the effects of microwave irradiation for resin-curing of carbon fiber/epoxy resin composite that was composed of discontinuous carbon fibers of 130 μm or 3 mm were investigated. The mechanical properties of carbon fiber/epoxy resin composite cured by microwave irradiation for 20 min at 120°C were similar to ones of the sample prepared by conventional oven for 180 min at 120°C. Microwavecured carbon fiber/epoxy resin composite had higher glass transition temperature than the one prepared by conventional oven. The relation between curing time and flexural modulus indicated that the curing velocity of microwave-irradiated carbon fiber/epoxy resin composite was 9 times faster than the one prepared by conventional oven. Furthermore, activation energies for resincuring reaction on microwave and conventional-cured carbon fiber/epoxy resin composite were estimated. The resin-curing reaction in carbon fiber/epoxy resin composite was promoted by microwave irradiation.