連続炭素繊維強化ポリカーボネートのオゾン酸化処理による強度向上

CFRP manufacturing method by using electro-activated deposition and the effect of reinforcement with carbon fiber circumferentially around the hole

The influence of BN on the mechanical properties of carbon fibers was investigated. It is found that the Young’s modulus of the derived carbon fibers becomes higher with BN amounts increasing through heat treatments at 1600–2350 °C, while the tensile strength increases at 1600 and 2000 °C and decreases at 2200 and 2350 °C with BN amounts increasing. Carbon fibers’ modulus and strength are increased by 6.6 and 7.4 % at maximum, respectively. It can be interpreted that fiber modulus is mainly determined by the preferred orientation of graphene planes and the shear modulus between them, while the strength of carbon fibers strength is determined by not only the two factors but also defects. Through X-ray diffraction, Raman spectra, and scanning electron microscope analysis, it is noted that BN catalysis enhances the preferred orientation of graphene planes and makes little change on the shear modulus but generates more defects above 2000 °C for fierce reaction.

In recent years, carbon fibre reinforced thermoplastics (CFRTP) are expected to be used as lightweight structural materials for mass-produced vehicles. CFRTP with thermoplastics as matrix allows us to weld them using melting of matrix by heating. We have been developing a direct resistance heating method, which uses carbon fibres as the resistance heating element. Carbon nanotube (CNT) is expected to be used as additive to FRP and we reported that the fibre/matrix interfacial shear strength was improved by grafting CNT on the surface of carbon fibres and tensile lap-shear strength was improved by using CNT grafted carbon fibre as the heating element for welding. For the practical use of CFRTP for structural parts, flexural strength is also necessary to be evaluated. In this study, flexural test was carried out to clarify the effect of CNT deposition time to the surface of carbon fibres on flexural strength of resistance welded CFRTP using CNT grafted carbon fibre as the heating element. The highest flexural strength was obtained when CNT10, for which CNT is grafted on the carbon fibres for deposition time of 10 min, was used for the heating element of resistance welding. In the case of CNT deposition time of 60 min, the lowest flexural strength was obtained because of the poor impregnation of the resin into the carbon fibre due to the excess CNT on the carbon fibres.

Polyacrylonitrile (PAN) precursor is a core precursor for the preparation of high-performance carbon fibers. Its unique chemical structure and physical properties directly contributes to the microstructure and mechanical properties of carbon fibers, and therefore affect the overall performance of pultruded composites. This study systematically investigated the influence of PAN precursor properties on the degree of graphitization, surface morphology and mechanical properties of carbon fibers by regulating the molecular weight distribution, stretching ratio and impurity content of PAN precursor, and analyzed the mechanism of action of carbon fiber properties on the interfacial bonding strength and tensile/bending properties of composites in combination with the pultrusion process. The results showed that when the filament stretchability was increased to 4.5 times, the axial orientation of carbon fibers increased by 18% and the tensile strength reached 520 MPa; Filaments with impurity content below 0.3% increase carbon fiber yield by 5.2% and interlaminar shear strength of composites by 23%. This study provides a theoretical basis for raw material screening and process optimization of high-performance carbon fibers and their composites.

ABSTRACTThis study employed polyethersulfone (PES) as a sizing agent for carbon fiber (CF) to enhance the interfacial bonding performance between CF and polyetheretherketone (PEEK). The effects of PES sizing on the thermal stability, surface characteristics, and composite properties were systematically investigated using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), contact angle measurements, and mechanical property tests. The results demonstrated that PES sizing significantly improved the thermal stability of CFs, with a mass loss of less than 0.2% at 450°C. After heat treatment at 380°C, the tensile strength of PES‐sized CF reached 2034.7 MPa, representing a 95.7% increase compared to commercial CF. The surface free energy of PES‐sized CF increased from 18.32 to 47.86 mJ/m2, accompanied by enhanced surface polarity, wettability, and interfacial adhesion with the PEEK matrix. Consequently, compared with ECF/PEEK composites, the tensile strength, flexural strength, and impact strength of PESCF/PEEK composites have increased by 20.11%, 24.47%, and 39.17%, respectively.

This paper reports on the cutting characteristics of a polycarbonate (PC) sheet stacked on a flexible underlay by a wedge indentation. In order to investigate the effect of underlay stiffness on sheared profile of PC sheet, the stiffness ratio kr in the thickness direction was varied. Indentation of a 42° center bevel blade into a 0.5mm thickness PC sheet that was stacked on the flexible underlay was carried out experimentally and numerically. Deformation profile of wedged PC sheet was observed by a CCD camera in order to reveal the effect of underlay on the cutting performance of the PC sheet. On the experimental works, it was found that the underlay mechanical properties affected the cutting load response and deformation features of the PC sheet. To discuss the effect of underlay stiffness on the deformation profile of the PC sheet, a finite element method (FEM) analysis with elasto-plastic model was conducted. Through the experiment and FEM simulation, it was revealed that the deformation profile of wedged PC sheet was remarkably related to the bent-up angle of the PC sheet, which was mainly caused by sinking and lateral elongation of the underlay. Moreover, in order to obtain a smart profile of the PC sheet, the stiffness ratio kr must be chosen in a suitable range.

In this study, polyphenylene sulfide (PPS) composite, which has ultra-high content of carbon fiber fabrics (CFF), was prepared from CFF and PPS nonwoven by a facile thermal-compressive method. The results show that the PPS composite composed of 80 wt% CFFs has optimal mechanical properties, where the tensile strength, fracture elongation, elastic modulus, flexural strength, flexural modulus, interlaminar shear strength, and impact strength reach to 1200.3 MPa, 20.3%, 25.7 GPa, 1305.6 MPa, 230.6 GPa, 110.3 MPa, and 348.6 KJ/m2, respectively. In addition, the volume resistivity, conductivity, and surface resistivity of the PPS composite with 80 wt% CFFs can reach to 1.3 × 10−2 Ω·cm, 74.9 S/cm, and 1.2 × 10−1 Ω·□ respectively. The increased interfacial layer and riveting effect between CFFs are responsible for outstanding structural stability and stress transformation, resulting in ultra-high strength and modulus of CFF/PPS composite, as well as the conductive performance.

Carbon fiber reinforced plastic (CFRP) is an excellent choice in the areas where weight reduction is important and multi-functionalization of CFRP, especially by adding sensor capabilities, is a promising approach to realize lightweight battery-free devices in structural health monitoring (SHM). In this study, we fabricated hybrid CFRP with Fe-Co fibers and evaluated the inverse magnetostrictive response characteristics. It was shown that the measured magnetic flux density of the CFRP fluctuates in response to cyclic bending load. It was also revealed that our Fe-Co fiber inserted CFRP has damage self-sensing ability. In addition, it seems that the optimization of design and more experimental and numerical investigation improves the capability of the hybrid CFRP with Fe-Co fiber as sensor composite materials.

A study on the flexural performance of 6-ply unidirectional hybrid composite laminates reinforced by carbon and basalt fibers is presented in this paper. The hybrid composites were fabricated following the resin transfer molding (RTM) process in an inter-ply configuration with varying plies of basalt fibers added to the surface of carbon laminate. Three-point bending test was carried out according to ASTM D790-10 at a span to depth ratio of 32. The laminates were examined by optical and scanning electron microscopy(SEM), which enabled a better comprehension of the failure modes. The results showed that various failure modes occurred through almost all of the layers and mainly concluded fiber buckling on the compressive side, shear failure on the middle layer, and fiber pull-out on the tensile side. Flexural properties of hybrid composites were strongly dependent on the basalt fibers added to the laminate. When adding two layers of basalt fibers to the laminates, flexural strength of hybrid composites increase most, and it can be seen that the flexural modulus decreased with increasing percentage of basalt fibers. And the experiments showed a positive hybridization effect by substituting carbon fibers with basalt fibers. Here, hybridization of carbon and basalt fibers can improve the balance of the mechanical properties of carbon fiber reinforced polymer(CFRP), thereby extending its application scope and reducing the cost.

Wear and mechanical properties of carbon fiber reinforced copper alloy composites

This paper evaluates the mechanical and thermal properties of 3D-printed short carbon fiber reinforced composites (sCFRPs). A numerical analysis was developed to predict the mechanical and thermal properties of the sCFRPs, which were verified via experimental tests. In the experiments, a novel technique was adopted by coating the sCFRPs with carbon fiber fabric and copper mesh to further improve its mechanical and thermal performance. Various copper meshes (60-mesh, 100-mesh and 150-mesh) were integrated with carbon fiber fabric to form a multilayer structure, which was then coated on the surface of Nylon 12-CF composite material (base material) to form a composite plate. The effects of the copper mesh on the mechanical and thermal properties of the composite plate were studied theoretically and experimentally. The results show that the addition of different copper meshes had a significant influence on the mechanical and thermal properties of the composite plate, which contained carbon fiber fabric, copper mesh and the base material. Among them, the mechanical and thermal properties of the composite plate with the 60-mesh copper mesh were significantly improved, while the improvement effect slowly declined with the increase in the thickness of the base material. The composite plate with 100-mesh and 150-mesh copper meshes had improved mechanical properties, whereas the influence on its thermal conductivity was limited. For thermal conductivity calculation, both the thickness and length directions of the heat transfer were considered. The comparative analysis indicated that the calculated values and experimental results are in excellent agreement, meaning that this numerical model is a useful tool for guiding the design of surface lamination for 3D-printed sCFRPs.

Carbon aqueous symmetric supercapacitors are attractive supercapacitor devices owing to the low-cost and high conductivity of porous carbons. However, the limited capacitive charge storage process in carbon symmetric capacitors in comparison to pseudocapacitors or asymmetric supercapacitors severely limit the energy density. The only effective strategy to enhance the energy density of carbon aqueous symmetric supercapacitor is to extend the cell voltage beyond the thermodynamic stability of aqueous electrolytes (1.23 V). Also, in recent studies, researchers have focused on preparing high performance carbon electrodes from commercial carbon fiber clothes by activating the surface usually through chemical and electrochemical routes. However, it is still a major challenge to realize a comprehensive electrochemical performance of high capacitances, excellent rate capability, stability and wide operational potential windows in the activated carbon fiber cloth electrodes. Herein, we successfully activated the surface of commercial carbon fiber clothes using a facile-one-step air calcination at 400 oC for 6 hours strategy to realize a remarkable improvement in surface area, porosity and electrochemical performance. The successful activation of the carbon fiber clothes is fully confirmed through BET tests, SEM, TEM, Raman and contact angle measurement tests. Specifically, the activated carbon exhibits a 450-fold increase in specific surface area (615 m2 g-1 for the activated carbon fiber clothes) as well as rich microporosity, excellent conductivity and superhydrophilicity, which would be beneficial in realizing easy electrolyte penetration and excellent capacitive performance. As expected, the activated carbon fiber cloth achieves ultrahigh areal capacitances of 1553 and 1600 mF cm-2 at 1 mA cm-2 in positive and negative potential windows, good rate capability and excellent cycling stability up to 20000 cycles in 1 M Na2SO4 electrolyte compared to a lowly capacitance of 1.53 mF cm-2 for the commercial carbon fiber clothes. Owing to the large overpotential for hydrogen and oxygen evolution, the activated carbon fiber cloth based symmetric supercapacitor is stable in a wide cell voltage of 2.0 V, displaying high volumetric and gravimetric energy densities of 7.62 mWh cm-3 and 18.2 Wh kg-1, respectively. The stability in this wide potential window is again confirmed using float voltage test method. These results not only report one of the best electrochemical performance of activated carbon fiber clothes, it also provides an effective and simple calcination activation method for realizing high capacitances and takes advantage of the wide operating voltage window to achieve high energy density in carbon textile supercapacitors. Importantly, our studies also showed that the electrochemical performances of metal oxides grown on carbon fiber clothes and annealed in air at 400 oC might be over-estimated as that temperature is sufficient to activate the surface of the carbon fibers.

Background: One of the major issues of carbon fiber reinforced polymeric composites is the weak interface between the phases, that supports crack propagation and leads to premature mechanical failure. The paper presents a study involving carbon fiber compatibilization with the polymeric matrix via oxidative treatment and the effect that the modified carbon fiber fabric has on the mechanical performance of its polyamide 6 composites. Methods: Thermoplastic polyamide 6 matrix/fabric based composites are obtained using carbon fiber fabric that is oxidized using K2Cr2O7/H2SO4 mixture in different reaction conditions. The oxidized carbon fiber surface is analysed using FTIR spectroscopy and the composite materials are mechanically tested in terms of tensile and flexural properties, the fracture cross section is analyzed by SEM and optical microscopy to evaluate the interface and the fracture mode. Results: FTIR spectroscopy showed that higher temperature oxidation generates more functional groups on the carbon fiber surface that are able to interact with the polymer, enhancing the interface strength. Tensile and flexural tests showed significant improvement of strength and stiffness when using surface oxidized carbon fabric, results owned to the excellent bonding between the matrix and the fibers that compose the fabric, illustrated by SEM and optical microscopy analysis. Conclusion: The obtained results prove that carbon fiber oxidation in certain condition is efficient for achieving stronger fiber/themoplastic matrix interface, by creating hydrogen bonding sites that prevent delamination and are able to improve the mechanical performance of the composites. Keywords: Carbon fiber fabric, laminated composites, oxidizing agent, polyamide 6, solvent impregnation, tensile strength, Young’s modulus.

The Al foams made by space-holder method were physically inserted into carbon fiber reinforced plastic (CFRP) composite thin-wall tubes to obtain the composite structure of Al foam-filled CFRP composite thin-wall tubes. Quasi-static compression tests of CFRP composite tubes, Al foams and Al foam-filled CFRP composite thin-wall tubes were carried out to study their compression properties. Meanwhile, digital image correlation (DIC) was applied to analyze their deformation modes. Furthermore, the compressive properties, energy absorption properties and failure modes of Al foam-filled CFRP composite thin-wall tubes at different temperatures (25-150℃) were studied. The results show that Al foams as fillers change the compression deformation behavior of CFRP composite thin-walled tubes from the scattering flowering failure of a single CFRP composite tube to the fiber layer fracture failure of a foam-filled tube. Comparing to CFRP composite thin-walled tubes, the stress fluctuations of Al foam-filled CFRP composite thin-wall tubes decrease obviously. With environmental temperature increasing, both the compressive properties and energy absorption properties of CFRP composite thin-walled tubes, Al foams and Al foam-filled CFRP composite thin-wall tubes decrease. But the interaction between Al foams and CFRP composite thin-walled tubes is enhanced, the enhancement effect of Al foams on CFRP composite thin-walled tubes is more obvious at high temperature.

The possibility to design composites with superior properties by incorporation of nanoscale reinforcing material still remains to be fulfilled. In the current study, bisphenol A diglycidyl ether‐based epoxy resin has been successfully modified with polyhedral oligomeric silsesquioxane (POSS) nanoparticles to give epoxy/POSS nanocomposites. Carbon fiber reinforced composites with different fiber orientations are processed via vacuum bagging technique using this composite as the matrix. Scanning electron microscopy indicated that POSS nanofillers homogeneously distributed in the matrix. As proved by the tensile, flexural, and interlaminar shear strength tests, the inclusion of POSS nanofillers in the polymer matrix has promoted significant improvements in the mechanical properties of the carbon fiber reinforced POSS/epoxy hybrid composites compared to the analogues with neat epoxy matrix. Thus, hybrid composites with exceptional properties are obtained via a straightforward modification in the matrix and a novel paradigm without using any expensive compound has been added to the library of nanocomposite formulations.