Mechanical Properties Of Carbon Research Articles

Flame retardant and mechanical properties of carbon fiber/novel phenolic resin sandwich composite laminates

This study investigated a novel phenolic resin that possesses the advantages of both epoxy and phenolic resins and significantly improves their disadvantages. This novel phenolic resin was impregnated into the carbon fiber woven to prepare a sandwich composite. Composites with sandwich structures were analyzed for their flame retardant and mechanical properties. The flame retardancy of the novel phenolic resin composite was similar to that of a pure phenolic resin composite without the processing disadvantages of pure phenolic resin, and these two composites were better than epoxy sandwich composites. The mechanical properties, such as facesheet, and core shear test results of the sandwich composite revealed that both epoxy and novel phenolic composites with a flame retardant added had poor interfacial bonding, resulting in lower strength than that of the neat sandwich composite.

Effects of vacuum thermal cycling, ultraviolet radiation and atomic oxygen on the mechanical properties of carbon fiber/epoxy shape memory polymer composite

The use of shape memory polymer composites as novel materials for next generation space deployable structures requires the study of the effect of space environment upon their properties. The resistance of carbon fiber/epoxy shape memory polymer composite to vacuum thermal cycling, ultraviolet radiation and atomic oxygen has been evaluated separately by using ground-based simulation facilities. The thermal cycling condition has a temperature range of −100 °C to +100 °C with cycle times of 0, 15, 30, and 45. The irradiation times of ultraviolet with a wavelength range of 250 nm–400 nm are 0, 80, 160, and 240 h. The atomic oxygen radiation has a translational energy of about 5 eV and a flux of about 2 × 1015 atoms/cm2 at the sample position, and the irradiation times are 0, 33, 66, and 100 h. The shape memory polymer composite specimens are compared in terms of morphology, tensile modulus, breaking strength and elongation at break before and after irradiation. Results show that thermal cycling increases tensile modulus but decreases the breaking strength and the elongation at break of material after 45 cycles. The effect of ultraviolet radiation on mechanical properties of materials depends on the radiation dose received. Atomic oxygen can negatively but slightly affect the mechanical properties of the material.

Computational Micromechanics Investigation of Percolation and Effective Electro-Mechanical Properties of Carbon Nanotube/Polymer Nanocomposites using Stochastically Generated Realizations: Effects of Orientation and Waviness.

The electrical and mechanical properties of carbon nanotube/polymer nanocomposites depend strongly upon several factors such as CNT volume fraction, CNT alignment, CNT dispersion and CNT waviness among others. This work focuses on obtaining estimates and distribution for the effective electrical conductivity, elastic constants and piezoresistive properties as a function of these factors using a stochastic approach with numerous CNT/polymer realizations coupled with parallel computation. Additionally, electrical percolation volume fraction and percolation transitional behavior is also studied. The effective estimates and percolation values were found to be in good agreement with experimental works in the literature. It was found that with increasing CNT volume fraction, the mechanical properties improved. However, due to the interaction of CNTs with one another through electrical tunneling, the conductivity and piezoresistivity properties evolved in a more complex manner. While the degree of alignment played a strong role in the effective properties making them anisotropic, the effect of waviness was found to be insubstantial.

Mechanical Properties of Carbon Fiber/Epoxy Composites Modified with Micro- and Nano-Sized Magnesium Oxide Particles

A systematic study on evaluating the effect of micro- and nano-sized magnesium oxide (MgO) particles on the mechanical properties of carbon fiber/epoxy composites was conducted by adding various contents of MgO particles into an epoxy resin matrix. The impact and flexural strengths were determined by the Charpy impact tests and three-point bending experiments, respectively. We found that the carbon fiber/epoxy composites filled with nano-MgO particles had higher mechanical strength than that of the carbon fiber/epoxy composites filled with micro-MgO particles. Both impact and flexural strength were enhanced by adding the proper content of nano-MgO particles. Although the impact strength was increased by adding micro-MgO particles, the flexural strength was decreased by adding micro-MgO particles. In addition, the influence of the nano- and micro-particles on the failure modes of the fiber/epoxy composites was also studied and is described.

The aggregation phenomenon of impurity atoms in Si and the properties of C-doped Si studied by first-principle calculations

The formation energy, band structures and mechanical properties of carbon (C)-doped single-crystal silicon (Si) with doping concentration from 1.56% to 6.25% were investigated in this paper by means of first-principle calculations. The different performances of the doped structures with C atoms scattered distributing and aggregated distributing in the Si lattice were emphatically discussed. The low impurity formation energy of X4Si60 (X = carbon (C), phosphorus (P), boron (B), nitrogen (N), hydrogen (H), aluminum (Al) or germanium (Ge)) indicates that the impurity atoms have a tendency to aggregate in Si and form a local tetrahedral SiX4 structure. The analyses of partial density of state illustrate that the strong combination of the central Si atom with the four adjacent C atoms results in good stability of the local tetrahedral SiC4 structure. The increasing concentration of the scattered doping C atoms leads to the decrease of band gaps from 1.174 eV to 0.624 eV and the change of doped structures from indirect band gap semiconductors into direct band gap semiconductors. However, the C4Si60 with C atoms aggregated distributing is still indirect band gap semiconductor with a larger band gap of 1.027 eV. The doping of C atoms enhances the charge transfer among atoms, which increases the strength of covalent bonds and results in the improvement of bulk moduli of doped structures. But the doping concentration and the arrangement positions of C atoms have few influences on the mechanical properties of doped structures.

Boosting both flame retardancy and mechanical properties of carbon fiber/epoxy composites via polycyclic phosphorus-nitrogen imidazole derivative

As a huge challenge to improve the mechanical properties while improving flame retardant performance in carbon fiber/epoxy resin composites. Hence, a novel flame retardant, polyaromatic ring phosphor-nitrogen imidazole derivative (PNB), was designed and used to prepare carbon fiber/epoxy composites (CF/EP-PNB). The optimal flame-retardant CF/EP-PNB composites exhibit excellent flame retardancy (the LOI of CF/EP-PNB composites with 10 % PNB could reach 33.8 % and pass V-0 grade in the UL-94 test and the residual chars could be as high as 70.7 %) and remarkable mechanical properties (the bending and impact strength of the CF/EP-PNB composites had increased by 41.5 % and 38.2 %, respectively).

Enhanced thermal and mechanical properties of carbon fiber/epoxy composites interleaved with graphene/SiCnw nanostructured films

In this work, novel graphene nanoplatelets (GnP)/silicon carbide nanowires (SiCnw) hybrid nanostructured films were successfully produced and employed as reinforcements for developing advanced laminated composites (CFRP). The one-dimensional continuous SiCnw uniformly interpenetrated within the hybrid films, which effectively connected and bridged adjacent GnP flakes, and facilitated heat flow across the interfacial boundaries in the through-thickness direction of the CFRP. The incorporation of GnP/SiCnw hybrids containing 5 wt% SiCnw significantly promoted the out-of-plane thermal conductivity of the CFRP, reaching 2.19 W/m·K, which represents increments of 186.3% and 54.2% compared to the neat CFRP and pure GnP film interleaved CFRP, respectively. Furthermore, the storage modulus and interlaminar shear strength of the CFRP were also evidently enhanced after introducing the GnP/SiCnw interleaves. This study proves the superiority of binary GnP/SiCnw films as reinforcements, and provides the guidance for the structural design of CFRP with excellent thermal and mechanical performances.

PVDF green nanofibers as potential carriers for improving self-healing and mechanical properties of carbon fiber/epoxy prepregs

Abstract The novel aligned polyvinylidene fluoride (PVDF) green core–shell nanofibers were reinforced to carbon fiber/epoxy prepregs and were manufactured through the vacuum bagging technique. Aligned nanofibers were achieved by suspending a grounded needle between the nozzle and the collector of electrospinning. The self-healing properties were tested through a periodic three-point bending test at an interval of 24 h at room temperature. The healing behavior was further confirmed through field-emission scanning electron microscopy coupled with dispersion X-ray spectroscopy (EDX) and an electrical conductivity test. The self-healing prepregs (1038.42 MPa) regained 66% of their original strength (1577.85 MPa) after the initial damage. EDX analysis confirmed the elements of the resin (VE (C, O)) and hardener (MEKP (C, O), CN (C, O, Co)) from the ruptured healing carriers. The damaged carbon prepregs healed by showing electrical conductivity of around 83%. The mechanical properties of self-healing composites were tested by tensile, flexural, and Izod impact tests and showed an increment in both flexural (7–12%) and impact strength (5–7%) with the addition of nanofibers. Overall, the research findings provided a design of eco-friendly carriers for carbon fiber-reinforced composites to obtain decent self-healing properties without deteriorating the mechanical strength.

Enhance the thermal conductivity and mechanical properties of CF/PPBESK thermoplastic composites by growth ZnO nanowires with tunable length and diameter on prepreg

This study proposes a simple and effective way to modify prepreg by vertically aligned ZnO nanowires (ZnO NWs) with tunable length and diameter to enhance the thermal conductivity and mechanical properties of Carbon fiber/Copoly (phthalazinone ether sulfone ketone) (CF/PPBESK) composites. The effect of the morphology of ZnO NWs on the thermal conductivity and mechanical performance of composites were investigated. Observed by scanning electron microscopy, the surface of the prepregs and the cross-section of the composites showed uniform vertical ZnO NWs dispersion and strong fiber-resin adhesion. The result indicated that the thermal conductivity of ZnO NWs/CF/PPBESK composites were increased by 47.4% after ZnO NWs introducing. Moreover, the flexural strength, compressive strength and ILSS of ZnO NWs-modified composites were increased by 16.5%, 54.7% and 24.1%. The high temperature mechanical properties of ZnO NWs/CF/PPBESK composites were also improved, which suggested that introduction of ZnO NWs between prepreg layers was an effective way to construct structure/function integrated composites.

Effect of Nanofiller on the Mechanical Properties of Carbon Fiber/Epoxy Composites under Different Aging Conditions.

In this study, carbon fiber-reinforced epoxy composites (CFRPs) containing multi-walled carbon nanotube (MWCNT) and halloysite nanoclay were fabricated. The effects of these nanofillers (MWCNT and nanoclay) on the tensile and flexural properties of the CFRPs under different aging conditions were studied. These aging conditions included water soaking, acid soaking, alkali soaking, and thermal shock cycling. The experimental results showed that, after accelerated aging, the mechanical performance of the CFRPs decreased. The performance degradation in the soaking environment depends on the immersion temperature and immersion medium. High-temperature accelerated the aging behavior of the CFRPs, resulting in low strength and modulus. The CFRPs were more vulnerable to acid soaking and alkali soaking than water soaking. The MWCNT and halloysite nanoclay are beneficial to improve the immersion aging resistance of the CFRPs, and the additions of nanofillers delayed the performance degradation under immersion aging conditions. However, nanofillers hardly improve the aging resistance of the CFRPs under thermal shock cycling condition. The fracture morphologies were observed by scanning electron microscopy (SEM) to reflect the failure modes of the CFRPs under various aging conditions. Differential scanning calorimeter (DSC) and fourier transform infrared (FTIR) spectroscopy tests were used to estimate the changes in the chemical structures and properties of epoxy resin and its composites under different conditions.

Исследование механических свойств углеродных молекулярных структур в виде многослойного графена с вертикально ориентированными углеродными нанотрубками

Исследование механических свойств углеродных молекулярных структур в виде многослойного графена с вертикально ориентированными углеродными нанотрубками

Investigating the Effects that Alternative Turbine Engine Fuels have on the Mechanical Properties of Carbon Fiber/Epoxy Composite

Investigating the Effects that Alternative Turbine Engine Fuels have on the Mechanical Properties of Carbon Fiber/Epoxy Composite

Defect engineering of carbon nanotubes and its effect on mechanical properties of carbon nanotubes/polymer nanocomposites: A molecular dynamics study

Molecular dynamics simulations have been performed to explore the effect of intrinsic defects of carbon nanotubes (CNTs) on the mechanical properties of CNTs/polyethylene (PE) composites. Three kinds of defects including single adatom defect, single vacancy defect and an adatom-vacancy pair defect have been considered here. The longitudinal Young's moduli of individual CNTs and CNTs/PE composites with different defects were calculated. On this basis, the interfacial interaction energy between CNTs and PE matrix and the adsorption behavior of PE molecular chains on the surface of CNTs were characterized. The results show that the elastic properties of individual CNTs and the interfacial characteristics between CNTs and matrix both contribute to the elastic properties of CNTs/PE composites. Meanwhile, due to different interaction energies, there exists three different adsorption modes of PE molecular chains on the surface of CNTs. Compared with the MD simulation results, the rule of mixture does not solidly hold in predicting the Young's modulus of composites for large defect degree.

Influence of Heat Inputs on Weld Profiles and Mechanical Properties of Carbon and Stainless Steel

This study examines the effect of heat input on the weld bead profile, microstructure and mechanical properties of single V- joint welded carbon and stainless-steel plates. The as-received sample steel plates were sectioned into eight pieces; dimension 75 X 30 X 10 mm thicknesses. Shielded metal arc welding (SMAW) of heat inputs 1250 and 2030 J/mm was used to produce full penetration bead on the plates. Although visual inspection indicated that some of the welds were macro defect free, austenitic stainless steel exhibited more weld distortions than the carbon steel and this was partially attributed to its lower carbon content and the width to depth aspect ratio of the weld profile aside the magnitude of the induced stress. For the carbon steel, as the heat input increased, the hardness value of both the heat affected zone and fusion zone increased. In contrast, for stainless steel, the hardness values were reasonably comparable within same weld region (HAZ or FZ) irrespective of heat input. Furthermore, the ultimate tensile strength of the stainless steel decreased as heat input increased while the ductility increased with an increase in heat input, in contrast to carbon steel, where both ductility and ultimate tensile strength generally decreased.

Fabrication and Characterization of Physical and Mechanical Properties of Carbon Nanotubes-Graphene-Based Sandwich Composite Pressure Sensor.

In this work, piezoresistive properties of graphene-multiwalled carbon nanotubes (MWCNTs) composites are investigated, characterized, and compared. Sandwich-type composite piezoresistive pressure-sensitive sensors (Ag/Graphene-MWCNT/Ag) with the same diameters, but different fabrication pressures and thicknesses were fabricated using the mortar and pestle/hydraulic press technique. To produce low-electrical-resistance contacts, both sides of the composite sensors were painted with silver (Ag) paste. All the sensors showed reductions in the direct current (DC) resistance ‘R’ with an increment in external uniaxial applied pressure. However, it was observed that higher fabrication pressure led to a lower resistance value of the composite, while the thicker samples give lower electrical conductivity and higher resistance than the thinner samples. The experimental data for all composite pressure sensors were in excellent agreement with the simulated results.

Optimization of Process Conditions for Continuous Growth of CNTs on the Surface of Carbon Fibers

Grafting carbon nanotubes (CNTs) is one of the most commonly used methods for modifying carbon fiber surface, during which complex device is usually needed and the growth of CNTs is difficult to control. Herein, we provide an implementable and continuous chemical vapor deposition (CVD) process, by which the novel multiscale reinforcement of carbon nanotube (CNT)-grafted carbon fiber is prepared. After exploring the effects of the moving speed and growth atmosphere on the morphology and mechanical properties of carbon nanotubes/carbon fiber (CNTs/CF) reinforcement, the optimal CVD process conditions are determined. The results show that low moving speeds of carbon fibers passing through the reactor can prolong the growth time of CNTs, increasing the thickness and density of the CNTs layer. When the moving speed is 3 cm/min or 4 cm/min, the surface graphitization degree and tensile strength of CNTs/CF almost simultaneously reach the highest value. It is also found that H2 in the growth atmosphere can inhibit the cracking of C2H2 and has a certain effect on prolonging the life of the catalyst. Meanwhile, the graphitization degree is promoted gradually with the increase in H2 flow rate from 0 to 0.9 L/min, which is beneficial to CNTs/CF tensile properties.

Enhanced interfacial and mechanical properties of carbon fiber/PEEK composites by hydroxylated PEEK and carbon nanotubes

The interfacial adhesion between carbon fiber (CF) and polyetheretherketone (PEEK) is poor due to their inert nature, limiting the mechanical properties of CF/PEEK composites. This study improved the interactions between CF and PEEK by sizing hydroxylated PEEK grafted multi-walled carbon nanotubes (HPEEK-g-MWCNT) synthesized via an esterification reaction. Molecular dynamics simulations and experiments were conducted to evaluate the microstructure and characterize the mechanical properties of CF/PEEK composites. A slightly decreased crystallinity of PEEK within modified composites resulted from the reduced nucleation effect of CF and inhibited PEEK mobility by HPEEK-g-MWCNT sizing. Hydrogen bonding and mechanical interlocking enhanced interface adhesion, and covalent bonds of HPEEK-g-MWCNT increased load transfer. These factors led to the flexural strength and interlaminar shear strength of HPEEK-g-MWCNT modified composites increased by 94.2% (669.7 MPa) and 55.2% (79.1 MPa) compared with control ones. The modification method of using chemically treated and grafted polymers like HPEEK-g-MWCNT would have great potential applications in thermoplastic composites.

Mechanical properties of carbon nanotubes/epoxy nanocomposites: Pre-curing, curing temperature, and cooling rate

The effects of composite fabrication, such as pre-curing, curing temperature, and cooling rate, were studied. In this work, the pre-curing was defined as heat treatment of Multi-Walled Carbon Nanotubes (MWNCTs) with Diglycidyl Ether of Bisphenol A (DGEBA) epoxy resin. Acid purified MWCNTs were characterized by Raman spectroscopy and Fourier Transform Infrared Spectroscopy (FTIR). The pre-curing facilitated bonding between MWCNTs and epoxy via the oxirane ring of DGEBA, which accelerated the curing process of epoxy and increased mechanical properties. The elevated curing temperature on the pre-cured sample further improved the composite’s mechanical properties by increasing interfacial bonding due to cross-linking. The rapid cooling using liquid nitrogen during pre-curing treatment prevented re-agglomeration of MWCNTs, showing smaller agglomerates and improving the mechanical properties. Agglomeration was characterized by scanning electron microscopy, while the bonding between MWCNTs and epoxy was examined by the length of fibre pull-out on the fracture surface. Tensile testing was deployed for mechanical properties characterization. The degree of cure was determined by FTIR and Differential Thermal Analysis (DTA).

Three-point bending properties of carbon fiber/honeycomb sandwich panels with short-fiber tissue and carbon-fiber belt interfacial toughening at different loading rate

The bending performances at different loading rate are studied for carbon fiber/honeycomb sandwich panels toughened by short aramid fiber tissues and carbon fiber belts. The carbon fiber belts are stitched cross the pores of honeycomb core for interfacial improvements. Three-point bending tests at different loading rates are carried out to investigate the effect of short aramid fiber tissue and carbon fiber belt on mechanical properties of carbon fiber/honeycomb sandwich specimens. Experimental results firstly indicate that the short-aramid-fiber interfacial toughening and carbon fiber belts toughening could both enhance the energy absorption and peak load of sandwich specimens at loading rates ranging from 2 mm/min to 500 mm/min. The failure modes and microstructures of toughened specimens are observed to analyse and explain the underlying mechanism of enhancing effect. It is illustrated that crack isolation phenomenon is found to be the main mechanism for avoiding interfacial damage of the sandwich specimen.

Comparative studies on the effect of fabric structure on mechanical properties of carbon fiber/epoxy composites

The application of carbon fiber/epoxy composites places more requirements on the selection of fabrics to meet the needs of structural components. Due to the large design space for reinforced fabric patterns, the relationship between the reinforcements and properties is essential to further understand. Four typical fabrics were manufactured in this research, named non-interlaced bidirectional fabrics, plain weave laminated fabrics, angle-interlock fabrics and bidirectional angle-interlock fabrics. The structural features of fabrics were analyzed by using representative geometric unit, and the symmetry properties were discussed based on group theory. Vacuum assistant resin transfer molding was adopted to obtain the corresponding resin matrix composite specimens. Quasi-static tensile and bending tests were conducted on these specimens. The stress-strain curves of specimens were illustrated, and the failure characterizations were also analyzed in mesoscopic scale. The results showed that the high crimp of yarns reduced the stability of composites. Both the tensile and flexural properties were affected by the curvature of yarns. The research results provided a theoretical basis for the selection of fabric structure and the application of carbon fiber/epoxy composites.