Surface Characteristics Of Carbon Fibers Research Articles

Nanoscale toughening of carbon fiber‐reinforced epoxy composites through different surface treatments

Interests in improving poor interfacial adhesion in carbon fiber‐reinforced polymer (CFRP) composites has always been a hotspot. In this work, four physicochemical surface treatments for enhancing fiber/matrix adhesion are conducted on carbon fibers (CFs) including acid oxidation, sizing coating, silane coupling, and graphene oxide (GO) deposition. The surface characteristics of CFs are investigated by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, interfacial shear strength, and interlaminar shear strength. The results showed that GO deposition can remarkably promote fiber/matrix bonding due to improved surface reactivity and irregularity. In comparison, epoxy sizing and acid oxidation afford enhancement of IFSS owing to effective molecular chemical contact and interlocking forces between the fiber and the matrix. Besides, limited covalent bonds between silane coupling and epoxy matrix cannot make up for the negative effects of excessive smoothness of modified CFs, endowing them inferior mechanical properties. Based on these results, three micro‐strengthening mechanisms are proposed to broadly categorize the interphase micro‐configuration of CFRP composite, namely, “Etching” “Coating”, and “Grafting” modifications, demonstrating that proper treatments should be chosen for combining optimum interfacial properties in CFRP composites. POLYM. ENG. SCI., 59:625–632, 2019. © 2018 Society of Plastics Engineers

Effect of surface treatment on surface characteristics of carbon fibers and interfacial bonding of PMMA resin composites

ABSTRACTCarbon fiber (CF) as reinforcement, self-crosslinking carbon fiber/PMMA prepared by prepolymer method (CF/PMMA) composite. The fiber is then melt blended with PMMA matrix to prepare PMMA composite. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to analyze and characterize the composites produced. The results show that the composite material prepared by separately modifying the fiber with plasma, aqueous ammonia and HNO3 solution. The mechanical properties of the composite materials prepared by the modified fiber are improved, and the fiber and the PMMA matrix shows better compatibility.

Interfacially reinforced unsaturated polyester carbon fiber composites with a vinyl ester-carbon nanotubes sizing agent

A amino-functionalized carbon nanotubes (CNTs)-containing sizing agent was prepared for improving the interface bonding and impact toughness of carbon fibers (CFs) reinforced unsaturated polyester (UP) composites. More reactive groups and better interfacial compatibility with UP make vinyl resin M7270 a more suitable polymer for preparing sizing agent for CF/UP composites when compared to epoxy, MR13006 and R806. The surface characteristics of CFs and the interfacial properties of the composites before and after surface modification were investigated. The observed uniformly dispersed CNTs-containing sizing agent on the CF surface obviously increased the surface roughness. The amount of polar functional groups and the wettability of CFs were significantly enhanced after the coating treatment. The interlaminar shear strength (ILSS) and impact toughness were enhanced by 32.3 and 55.2%, respectively. The sizing agent effectively enhanced the interfacial adhesion by improving the surface energy, and increasing chemical bonding and mechanical interlocking.

Polyurethane elastomer as a matrix material for short carbon fiber reinforced thermoplastic composites

Short carbon fibers (CF) with different surface sized (epoxy (EP) and polyurethane (PU)) were used as reinforcing agent in thermoplastic polyurethane (TPU) based composites. Composites containing 5, 10, 15, and 20 weight % sized and desized CFs were prepared by using melt-mixing method. The surface characteristics of CFs were examined by energy dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectroscopy (FTIR). Tensile testing, shore hardness test, dynamic mechanical analysis (DMA) and melt flow index (MFI) test were performed for determining final composite properties. The dispersion of CFs in TPU matrix was examined by scanning electron microscopy (SEM). Tensile strength, Youngs’ modulus and Shore hardness of TPU were enhanced by the addition of sized CFs. About two-fold improvement for tensile strength and ten-fold improvement for Youngs’ modulus were observed with the incorporation of 20 wt% EP-CF and PU-CF in TPU. The storage modulus of PU-CF containing composites was higher than those of TPU and other composites. No remarkable change was observed in MFI value of TPU after CF loadings. Processing conditions in this work was suitable for composite production. Sized CFs exhibited better dispersion with regard to desized CF due to the stronger adhesion of TPU matrix to fiber surface.

Effects of particle size and distribution of the sizing agent on carbon fiber/epoxy composites interfacial adhesion

This article aims to study the effects of particle size and distribution (PSD) of sizing agent on surface physical and chemical properties of the carbon fiber. Five kinds of sizing agents with various PSD named P‐1 to P‐5 sizing were applied in order to investigate the influences on interfacial properties between the carbon fiber and the matrix. The surface characteristics of carbon fibers were investigated to determine morphology, chemical composition, surface energy, interfacial thickness, and interlaminar shear strength (ILSS). The results revealed that, as the particle size decreasing, the O1s/C1s composition ratios, surface energy and the interfacial thickness show a growing trend whereas the surface roughness reduces mildly. Similarly, the ILSS of the carbon fiber/epoxy composites have also increased by more than 8% with the decreased particle size. This demonstrates that small particle size with multimodal PSD in sizing is advantageous for effective wetting and force transition in the interfacial adhesion. Actually, when the mean particle size is around 110 nm (P‐3 sizing), the emulsion droplets can repair the surface irregularity and hold back excessive stress most remarkably, leading to optimal contributions to the improvement of ILSS. Based on these results, a mechanism concerning particle arrangement in sizing and interfacial strengthening in carbon fiber/epoxy composites was proposed, which provided a reasonable explanation to analyze the effects of PSD in sizing and interfacial bonding. POLYM. COMPOS., 39:E2036–E2045, 2018. © 2017 Society of Plastics Engineers

Optimization of interfacial properties of carbon fiber/epoxy composites via a modified polyacrylate emulsion sizing

The adhesion behavior of epoxy resin to carbon fibers has always been a challenge, on account of the inertness of carbon fibers and the lack of reactive functional groups. In this work, a modified polyacrylate sizing agent was prepared to modify the interface between the carbon fiber and the epoxy matrix. The surface characteristics of carbon fibers were investigated to determine chemical composition, morphology, wettability, interfacial phase analysis and interfacial adhesion. Sized carbon fibers featured improved wettability and a slightly decreased surface roughness due to the coverage of a smooth sizing layer, compared with the unsized ones. Moreover, the content of surface activated carbon atoms increased from 12.65% to 24.70% and the interlaminar shear strength (ILSS) of carbon fiber/epoxy composites raised by 14.2%, indicating a significant improvement of chemical activity and mechanical property. SEM images of the fractured surface of composites further proved that a gradient interfacial structure with increased thicknesses was formed due to the transition role of the sizing. Based on these results, a sizing mechanism consisting of chemical interaction bonding and physical force absorption was proposed, which provides an efficient and feasible method to solve the poor adhesion between carbon fiber and epoxy matrix.

Microstructure and mechanical behaviors of T700 carbon fiber reinforced C/SiC composites via precursor infiltration and pyrolysis

A new tow-spreading technology was employed to spread T700SC 12K fibers to a width of 12mm, based on which plain weave carbon cloth with a low areal density of 100g/m2 and the thickness of 0.1mm was obtained. 2D C/SiC composites reinforced by such T700 carbon cloth, together with T300 3K plain weave carbon cloth (200g/m2 areal density) for comparison, were prepared by precursor infiltration and pyrolysis process. Chemical vapor deposition pyrocarbon (PyC) interphase was also used to modify the surface structures of both fiber reinforcements. The mechanical behaviors of the composites were predominantly affected by the in situ strength of carbon fibers as well as the relationship between the surface characteristics of carbon fibers and the material interface. T300 composites failed in a brittle mode, whereas T700 composites displayed a non-brittle fracture behavior. Mechanical properties of both composites were improved by PyC interphase. T700 composites with PyC interphase had a homogenous fiber-matrix structure and exhibited the optimum mechanical property, with the flexural strength, flexural modulus and shear strength of 425±23MPa, 37±3GPa and 24±2MPa, respectively.

Effect of surface treatment on surface characteristics of carbon fibers and interfacial bonding of epoxy resin composites

This paper aims to study the effect of aqueous ammonia etching, nitric acid oxidation and aqueous ammonia/nitric acid combined treatment on surface characteristics of carbon fibers (CFs) and interfacial bonding properties of CF/epoxy resin composites. The morphologies and chemical compositions of pristine CFs and treated CFs were characterized using a Scanning Electron Microscope (SEM), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectroscopy (XPS). It was found that the surface of treated CFs has greater roughness compared with the surface of pristine CFs; moreover, the surface roughness is at maximum with the aqueous ammonia/nitric acid combined treatment. No obvious change in chemical composition takes place with aqueous ammonia etching of CFs. On the other hand, the oxygen content on the surface of CFs increases with nitric acid oxidation and aqueous ammonia/nitric acid combined treatments. The effect of surface treatment on the wettability, single filament tension strength, and interfacial shear strength (IFSS) of CF/epoxy resin composites was measured. Results show that the wettability of CFs against distilled water improves with the surface treatment. The wettability optimum with the aqueous ammonia/nitric acid combined treatment. Compared with pristine CFs, there is only a slight loss in tension strength with the treated CFs. In addition, the IFSS value of composites increased greatly. The IFSS of aqueous ammonia/nitric acid treated carbon fibers reinforced with epoxy resin composites increases by 46.36 % compared with pristine ones, This resulted from the combined action of the increase in the carbon fiber surface roughness and surface oxygen containing functional groups.

Preparation and characterization of epoxy/carbon fiber composite capacitors

Capacitors based on structural carbon fiber electrodes and epoxy‐based gel polymer electrolyte have been fabricated. The electrochemical properties of electrolytes and capacitors were evaluated by linear sweep voltammetry, cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. Surface modification of carbon fibers was carried out by oxidation, and the structural and surface characteristics of carbon fibers were investigated by scanning electron microscope, Brunauer–Emmet–Teller, and Boehm titration. The results showed that the electrochemical stability window of the electrolyte reached 2.75 V and the ionic conductivity reached the order of 10−5 S/cm at room temperature. Surface modification of carbon fiber by oxidation can enlarge fiber area and strengthen fiber chemical activity, as well as its energy storage ability. The specific capacitance of epoxy/carbon fiber composite capacitor was obtained as high as 3.0 F/g with good cycling performance. POLYM. COMPOS., 36:1447–1453, 2015. © 2014 Society of Plastics Engineers

The Morphologies of Nano Carbon Growing <i>In Situ</i> by Catalytic Chemical Vapor Deposition

In order to improve surface characteristics of carbon fibers, using nickel granules as catalysts, nano carbon with different morphologies was deposited in-situ on the surface of carbon fibers by the method of Chemical Vapor Deposition (CVD). The observations by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) indicated that keeping the excellent performance of plating nickels catalyst and a suitable deposition rate of Pyrogenation Carbon (PyC) are the key factors for getting Carbon Nanotube and Carbon Nanofiber (CNT/CNF). In this experiment, the optimum operation conditions are: plating time at 5min, deposition temperature at 1173K, deposition time at 2 hours, flow of C3H6, H2 and N2 at 30, 200 and 400ml/min respectively, deposition pressure at 700-1000Pa. Evolution rules of nano carbon are explained in growth mechanism of Catalytic Chemical Vapor Deposition (CCVD).

A study of the effect of oxygen plasma treatment on the interfacial properties of carbon fiber/epoxy composites

AbstractIn this work, effects of the interface modification on the carbon fiber‐reinforced epoxy composites were studied. For this purpose, the surface of carbon fibers were modified by oxygen plasma treatment. The surface characteristics of carbon fibers were studied by X‐ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), dynamic contact angle analysis (DCAA), and dynamic mechanical thermal analysis (DMTA), respectively. The interlaminar shear strength (ILSS) was also measured. XPS and AFM analyses indicated that the oxygen plasma treatment successfully increased some oxygen‐containing functional groups concentration on the carbon fiber surfaces, the surface roughness of carbon fibers was enhanced by plasma etching and oxidative reactions. DCAA and DMTA analyses show that the surface energy of carbon fibers increased 44.9% after plasma treatment for 3 min and the interfacial bonding intensities A and α also reached minimum and maximum value respectively. The composites exhibited the highest value of ILSS after oxgen plasma treated for 3 min. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effect of Fiber Surface Treatment on Wear Characteristics of Carbon Fiber Reinforced Polyamide 6 Composites

Ozone modification method and air-oxidation were used for the surface treatment of polyacrylonitrile(PAN)-based carbon fiber. The surface characteristics of carbon fibers were characterized by X-ray photoelectron spectroscopy (XPS). The interfacial properties of carbon fiber reinforced polyamide 6 (CF/PA6) composites were investigated by means of the single fiber pull-out tests. As a result, it was found that IFSS values of the composites with ozone treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PA6 matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PA6 composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the wear resistance of CF/PA6.

Surface oxidation of carbon fibre on tribological properties of PEEK composites

In this work, ozone modification method and air oxidation were used for the surface treatment of polyacrylonitrile (PAN) based carbon fibre. The surface characteristics of carbon fibres were characterised by X-ray photoelectron spectroscopy. The interfacial properties of carbon fibre reinforced PEEK (CF/PEEK) composites were investigated by means of the single fibre pull-out tests. As a result, it was found that IFSS values of the composites with ozone treated carbon fibre are increased by 60% compared with that without treatment. X-ray photoelectron spectroscopy results show that ozone treatment increases the amount of carboxyl groups on carbon fibre surface, thus the interfacial adhesion between carbon fibre and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibres on the tribological properties of CF/PEEK composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fibre and PEEK matrix. Thus the wear resistance was significantly improved.

Interfacial features of polyamide 6 composites filled with oxidation modified carbon fibres

Polyacrylonitrile (PAN)-based carbon fibres were surface treated by ozone modification method and air-oxidation treatment. The interfacial properties of carbon fibre reinforced polyamide 6 (CF/PA6) composites were investigated by means of the single fibre pull-out tests. The surface characteristics of carbon fibres were characterized by X-ray photoelectron spectroscopy (XPS). As a result, it was found that interfacial shear strength values of the composites with ozone-treated carbon fibre are greatly increased. XPS results show that ozone treatment increases the amount of carboxyl groups on the carbon fibre surface, thus the interfacial adhesion between carbon fibre and PA6 matrix is effectively promoted. The effect of surface treatment of carbon fibres on the tribological properties of CF/PA6 composites was comparatively investigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fibre and PA6 matrix. Thus the wear resistance was significantly improved.

Interfacial studies on the ozone and air‐oxidation‐modified carbon fiber reinforced PEEK composites

AbstractIn this work, ozone modification method and air‐oxidationwere used for the surface treatment of polyacrylonitrile(PAN)‐based carbon fiber. The surface characteristics of carbon fibers were characterized by XPS. The interfacial properties of carbon fiber‐reinforced (polyetheretherketone) PEEK (CF/PEEK) composites were investigated by means of the single fiber pull‐out tests. As a result, it was found that IFSS (interfacial shear strength) values of the composites with ozone‐treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that ozone treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PEEK matrix is effectively promoted. The effect of surface treatment of carbon fibers on the tribological properties of CF/PEEKcomposites was comparativelyinvestigated. Experimental results revealed that surface treatment can effectively improve the interfacial adhesion between carbon fiber and PEEK matrix. Thus the wear resistance was significantly improved. Copyright © 2009 John Wiley & Sons, Ltd.

Surface characteristics of carbon fibers modified by direct oxyfluorination

The effect of oxyfluorinated conditions on the surface characteristics of carbon fibers was investigated. Infrared (IR) spectroscopy results indicated that the oxyfluorinated carbon fibers showed carboxyl/ester groups (C O) at 1632 cm −1 and hydroxyl groups (O H) at 3450 cm −1 and had a higher O H peak intensity than that of the fluorinated ones. X-ray photoelectron spectroscopy (XPS) results for the fibers also showed that oxyfluorination introduced a much higher oxygen concentration onto the fiber surfaces than fluorination with F 2 only. Additionally, contact-angle results showed that the surface was better wetted by following oxyfluorination and that the polarity of the surface was increased by increasing the oxyfluorination temperature.

Interfacial studies on the O 3 modified carbon fiber-reinforced polyamide 6 composites

In this work, O 3 modification method was used for the surface treatment of polyacrylonitrile (PAN)-based carbon fiber. The surface characteristics of carbon fibers were characterized by X-ray photoelectron spectroscopy (XPS). The interfacial properties of carbon fiber-reinforced polyamide 6 (CF/PA6) composites were investigated by means of the single fiber pull-out tests. As a result, it was found that IFSS values of the composites with O 3 treated carbon fiber are increased by 60% compared to that without treatment. XPS results show that O 3 treatment increases the amount of carboxyl groups on carbon fiber surface, thus the interfacial adhesion between carbon fiber and PA6 matrix is effectively promoted.

INFLUENCE OF OXYFLUORINATION ON TRANSPORT MECHANICAL PROPERTIES OF PAN-BASED CARBON FIBERS

In this work, the effect of oxyfluorination on surface characteristics of carbon fibers was investigated in terms of fracture toughness and crack resistance properties of the epoxy matrix composites. The surface properties of the carbon fibers were determined by the acid-base values, X-ray photoelectron spectroscopy (XPS), and FT-IR measurements. And their fracture toughness of the composites was studied in critical stress intensity factor K IC and critical energy release rate mode II G IIC . As the experimental XPS results showed, O 1S / C 1S ratio was increased by oxyfluorination, due to the oxygen-containing functional groups and the format in the C – F x bonds on carbon fiber surfaces. It was found that the fracture toughness and crack resistance of the composites were improved by the oxyfluorination, which could probably be attributed to the increase of the degree of adhesion at the interfaces between the carbon fibers and epoxy resin matrix in the present composite system.

Influence of Oxygen Plasma Treatment on Impact Behaviors of Carbon Fibers-Reinforced Composites

In this work, effects of the oxygen plasma on surface characteristics of carbon fibers were investigated in impact strengths of the carbon fibers-reinforced composites. The surface properties of the carbon fibers were determined by acid-base values, FT-IR, and X-ray photoelectron spectroscopy (XPS). Also, the mechanical properties of the composites were studied in impact strength measurements. As experimental results, the O1S/C1S ratio of the carbon fiber surfaces treated by oxygen plasma was increased compared to that of untreated ones, possibly due to development of oxygen-containing functional groups. The mechanical properties of the composites, including impact strength had been improved in the oxygen plasma on fibers. These results indicate that the oxygen plasma can lead to an increase in the adhesion between fibers and matrix in a composite system.

Surface analysis of plasma grafted carbon fiber

The surface characteristics of carbon fibers were studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and wetting measurements. The surface of carbon fiber was modified by means of plasma graft silsesquioxane. The oxygen/carbon and silicon/carbon ratio increased rapidly after treatments. Fitting the C 1s, O 1s, and Si 2p spectra demonstrated that new photopeaks were emerged, which were indicated C–Si, Si–O groups, respectively. The degree of surface roughness and the wettability of carbon fiber surface were both increased by plasma graft silsesquioxane. The results may shed some light on the design of the appropriate surface structure, which could react with resin, and the manufacture of the carbon fiber reinforced composites.