Surface Energy Of Carbon Fibers Research Articles

Construction of Polar Functional Groups on the Surface of a High-Modulus Carbon Fiber and Its Effect on the Interfacial Properties of Composites.

The interfacial bonding between carbon fibers and the resin matrix affects the mechanical properties of carbon fibers, and the increase of modulus brings a challenge to the interfacial properties of carbon fibers. The traditional anodic oxidation with ammonium bicarbonate as an electrolyte has a limited effect on the surface treatment for high-modulus carbon fibers. In this paper, anodic oxidation with an acidic electrolyte is used to treat high-modulus carbon fibers. The influence mechanism of a graphitized structure on the anodizing reaction of the carbon fiber surface was studied. Raman spectroscopy, XPS, scanning electron microscopy, dynamic contact angle, and micro-debonding were used to characterize the effect of surface treatment and its influence on interfacial properties. The results show that with a certain concentration of sulfuric acid as an electrolyte, the oxidation of the carbon fiber surface with high modulus occurs more on the graphite boundary defects. Carbonylation occurs mainly in carbon fibers with high modulus. The surface of the carbon fiber with a relatively low modulus is mainly hydroxylated and carboxylated. The surface energy and interfacial properties of high-modulus carbon fibers were improved effectively by anodic oxidation with sulfuric acid as an electrolyte. Under the condition that the mechanical properties of carbon fibers are not decreased, the surface energy of high-modulus carbon fibers with 352 GPa increases from 36.17 to 45.41 mN/m, and the interfacial shear strength (IFSS) with the epoxy resin increases by 80.8% from 34.9 to 63.1 MPa. When the fiber modulus is 455 GPa, the surface energy of the carbon fiber increases from 32.32 to 43.73 mN/m, and IFSS increases by 253.4% from 11.8 to 41.7 MPa.

Effect of Sizing Agents on Surface Properties of Carbon Fibers and Interfacial Adhesion of Carbon Fiber/Bismaleimide Composites.

Physicochemical, surface, and mechanical properties of three batches of T800 grade carbon fibers (CFs) treated with three kinds of sizing agents and Toray T800H CFs were characterized to study the effect of sizing agents on surface properties. Scanning electron microscopy for morphology, atomic force microscopy calculations, and results for the content of sizing agents showed that sizing agent B improved the surface roughness and CFs with high content of sizing agent always presented small surface roughness in a certain content range 1.2–1.6%. Surface energy of CFs was calculated by Young’s contact angle using the test results with water and glycol, and contact angles with LY-1 and modified-AC531 were also acquired. The results proved that CFs of sizing agent group B had the highest average surface energy and the lowest average contact angles with both LY-1 and modified-AC531. From both single-filament and tensile strength test results, the average strength of CFs of sizing agent group B was found to be the lowest, which indicated that sizing agent B had an influence on tensile strength decrease of T800 grade CFs. Comparing the results of interfacial shear strength both in a natural dry state and after hygrothermal treatment, high surface energy was found to be the key element to obtain high interfacial adhesion between T800 grade CFs and bismaleimide, and high surface roughness and low contact angle also played important roles. Among sizing agents A, B, and C, A had an effect on the interfacial shear strength decrease of CFs in the natural dry state, while C had that after hygrothermal treatment.

Chemical grafting of salicylaldehyde onto carbon fiber for enhancing interfacial strength of silicone resin composites

AbstractChemical grafting of salicylaldehyde onto the surface of carbon fibers (CFs) via the bridging 3‐aminopropyltriethoxysilane was reported to improve interfacial properties of composites. Surface microstructures, compositions, wettability, and surface energy of CFs before and after modification were studied. Single‐fiber tensile strength (TS) was also determined to evaluate the damage degree brought by using the grafting strategy to the fiber intrinsic strength. The interfacial shear strength of composites was characterized to confirm interfacial compatibility and adhesion between CFs and matrix resin. Antihydrothermal aging experiments were also carried out to evaluate their environmental stability. As a result, the introduced salicylaldehyde molecules could increase polar functional groups, roughness, and interfacial wettability of CFs, and thus enhance interfacial strength as well as the hydrothermal aging resistance of the resulting composites significantly. Such sharp improvements could be due to the increases of interfacial compatibility, mechanical interlocking, and chemical bonding at the interfacial region via the formation of salicylaldehyde‐modified interface. Meanwhile, the modification procedure does not decrease fiber TS.

Growth of carbon black onto continuous carbon fiber to produce composites with improved mechanical and interfacial properties: A step closer to industrial production

Performance of carbon fiber (CF) reinforced composites mainly depends on the tensile strength and interfacial bonding strength between fiber and the matrix. However, most of the surface modification technologies for CF may result in decrease in its tensile strength in both laboratory scale and commercial production. Herein, carbon black (CB) was decorated onto the surface of CF by chemical vapor deposition (CVD) method. SEM, TEM and AFM characterizations showed that CB significantly changed the morphology of CF. The results of dynamic contact angle text (DCAT) demonstrated that the surface energy of CF was increased due to the loading of CB. Upon the decoration by CB, IFSS, ILSS and impact strength of CF/epoxy composites were enhanced, corresponding to 46.84%,29.11% and 48.24%, respectively, and the reinforcing and toughening mechanisms have also been discussed. Besides, the results of tensile tests for single fiber showed that the tensile strength (TS) of CB-decorated CF was higher compared with that of original CF. Meanwhile, this modification method for CF could serve as a basis for realizing the industrialization online production.

Enhancing strength and toughness of carbon fibers reinforced rigid polyurethane composites with low fiber content

The cooperative improvement of strength and toughness of rigid polyurethane (RPU) is a vital requirement as a structural material. In this work, 0.2 wt% short carbon fibers (CFs) reinforced RPU composites with high strength and toughness were prepared. The effects of fiber surface treatment and the mechanical properties of RPU composites were studied. Scanning electron microscopy (SEM) was performed to observe the surface morphology of the CFs as well as the fracture surfaces of the composites. Fourier-transform infrared spectroscopy (FT-IR) and contact angle instrument were used to analyze the surface functional groups and the surface energy of CFs, respectively. The results indicated that the surface roughness, the content of OH groups and the surface energy of carbon fibers increased after oxidation modification. Compared with pure RPU, the tensile, bending and impact strength of modified CFs/RPU composites were increased by 38.8%, 22.4% and 71.4%, respectively. Dynamic thermomechanical analysis (DMA) and SEM indicated the positive effects of oxidation modification on the interfacial bonding between modified CFs and RPU matrix.

Improvement of interfacial properties in bismaleimide composites using functionalized graphene oxide grafted carbon fiber

A hierarchical reinforcement, which was used to improve the interfacial properties of bismaleimide (BMI) composites, was prepared by grafting functionalized graphene oxide (GO) onto a carbon fiber surface. The GO and carbon fibers were first functionalized separately to create interactional functional groups on their surfaces. The grafting process was then realized by an amidation reaction of the amine and acyl chloride function groups formed on GO and carbon fibers, respectively. The surface groups of functionalized GO and carbon fibers were identified by an X‐ray photoelectron spectroscopy (XPS). The resulting reinforcement was further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic contact angle analysis. Experimental results showed that the functionalized GO were successfully grafted onto the carbon fibers surfaces and significantly increased the surface energy of carbon fibers. The study also indicated that the prepared hierarchical reinforcement could significantly improve the interfacial adhesion of resulting BMI composite. POLYM. ENG. SCI., 58:886–893, 2018. © 2017 Society of Plastics Engineers

Effect of a multiscale reinforcement by carbon fiber surface treatment with graphene oxide/carbon nanotubes on the mechanical properties of reinforced carbon/carbon composites

An effective carbon fiber/graphene oxide/carbon nanotubes (CF-GO-CNTs) multiscale reinforcement was prepared by co-grafting carbon nanotubes (CNTs) and graphene oxide (GO) onto the carbon fiber surface. The effects of surface modification on the properties of carbon fiber (CF) and the resulting composites was investigated systematically. The GO and CNTs were chemically grafted on the carbon fiber surface as a uniform coating, which could significantly increase the polar functional groups and surface energy of carbon fiber. In addition, the GO and CNTs co-grafted on the carbon fiber surface could improve interlaminar shear strength of the resulting composites by 48.12% and the interfacial shear strength of the resulting composites by 83.39%. The presence of GO and CNTs could significantly enhance both the area and wettability of fiber surface, leading to great increase in the mechanical properties of GO/CNTs/carbon fiber reinforced composites.

Interfacial Properties Improvement of Carbon Fiber Reinforced Epoxy Composites Modified with Carbon Nanotubes

In order to improve the interfacial properties in carbon fiber (CF) reinforced epoxy (EP) composites, we directly introduced amidized carbon nanotubes (CNTs) dispersed in the fiber sizing onto the fiber surface. Morphology and surface energy of CFs were examined by scanning electron microscopy (SEM) and dynamic contact angle analysis test (DCAT). Tensile strength (TS) was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS and impact toughness were enhanced simultaneously.

A high efficient method for introducing reactive amines onto carbon fiber surfaces using hexachlorocyclophosphazene as a new coupling agent

To improve the interfacial properties of carbon fiber (CF) reinforced composites, an innovative and simple functionalized strategy has been proposed by grafting 4,4′-oxydianiline (ODA) onto carbon fiber surface using hexachlorocyclophosphazene (HCCP) as a novel coupling agent at mild reaction conditions. The chemical composition of the CF surface was confirmed by X-ray photoelectron spectra (XPS). The surface topography and surface energy of CF were examined by atomic force microscope (AFM) and dynamic contact angle tests (DCA), respectively. The interfacial shear strength (IFSS) of CF reinforced composites was studied by microbond test. The tensile strength of CF was measured by single filament tensile test. After functionalization treatment, the grafted amine groups on the fiber surface enhanced the surface wettability of modified CF and formed strong chemical bonding between fiber and matrix, improving the interfacial adhesion strength of composites. The interfacial shear strength of modified CF reinforced composites increased by 71.2% compared with that of desized CF. The interfacial enhancement mechanism was also discussed in detail. Moreover, the modified CF almost kept the original mechanical properties after functionalization.

Improved interfacial properties of carbon fiber/unsaturated polyester composites through coating polyhedral oligomeric silsesquioxane on carbon fiber surface

Carbon fibers were coated with E51 plus Methacryl-POSS together in an attempt to improve the interfacial properties between carbon fibers and unsaturated polyester resins matrix. Atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were performed to characterize the changes of carbon fiber surface. AFM results show that the coating of E51 plus POSS significantly increased the carbon fiber surface roughness. XPS indicates that silicon containing functional groups obviously increased after modification. Dynamic mechanical analysis was carried out to investigate the surface energy of carbon fiber. Force modulation atomic force microscopy (FMAFM) and Interlaminar shear strength (ILSS) were used to characterize the interfacial properties of the composites. ILSS was increased by 21.9 % after treatment.

Interfacial microstructure and properties of carbon fiber-reinforced unsaturated polyester composites modified with carbon nanotubes

To improve the interfacial properties in carbon fiber (CF)-reinforced unsaturated polyester (UP) composites, we directly introduced functionalized carbon nanotubes dispersed in the fiber sizing onto the fiber surface. For comparing the influence of polymer type on sizing effect, two different polymers (UP MR13006 and water-soluble epoxy (EP)) were used to prepare sizing agent. Morphology and surface energy of CFs were examined by scanning electron microscopy and dynamic contact angle analysis test. Tensile strength was investigated in accordance with ASTM standards. Mechanical properties of the composites were investigated by interlaminar shear strength (ILSS) and impact toughness. Test results indicate that TS, ILSS, and impact toughness were enhanced simultaneously. For UP matrix, the sizing agent containing UP has better reinforcing and toughening effect than the sizing agent containing water-soluble EP.

Improved interfacial adhesion in carbon fiber/polyether sulfone composites through an organic solvent-free polyamic acid sizing

An organic solvent-free polyamic acid (PAA) nanoemulsion was obtained by direct ionization of the solid PAA in deionized water, with the average particle size of 261nm and Zeta potential of −55.1mV, and used as a carbon fiber sizing to improve the interfacial adhesion between the carbon fiber and polyether sulfone (PES). The surface characteristics of PAA coated carbon fibers were investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy and dynamic contact angle measurement. The results demonstrated that a continuous and uniform PAA sizing layer was formed on the surface of carbon fibers, and the surface energy of carbon fibers increased from 42.91 to 54.55mN/m after sizing treatment. The single fiber pull-out testing was also performed, which showed the increased interfacial shear strength (IFSS) of carbon fiber/PES composites from 33.6 to 49.7MPa by 47.9%. The major reasons for the improved interfacial adhesion were the increased van der Waals forces between the PES matrix and sizing layer as well as the chemical bonding between the sizing layer and carbon fiber surface. Furthermore, the PAA sizing also presented a positive effect on the interfacial adhesion of carbon fiber/PES composites under hydrothermal condition.

Properties of carbon fiber sized with poly(phthalazinone ether ketone) resin

AbstractWe studied thermoplastic poly(phthalazinone ether ketone) (PPEK) resin as a sizing agent on carbon fiber, with emphasis on its thermal stability, surface energy, wetting performance, and interfacial shear strength (IFSS). X‐ray photoelectron spectroscopy characterization was carried out to study the chemical structure of sized/unsized carbon fibers. Scanning electron microscopy and atomic force microscopy were used to characterize surface topography. TGA was used to analyze the thermal stability. Meanwhile, contact angle measurement was applied to analyze the compatibility between the carbon fibers and PPEK and the surface energy of carbon fibers. IFSS of carbon fiber/PPEK composite was examined by microbond testing. It is found that carbon fibers uniformly coated with PPEK resin had better thermal stability and compatibility with PPEK resin than the uncoated fiber. The contact angle is 57.01° for sized fibers, corresponding to a surface energy of 49.96 mJ m−2, much smaller than that for unsized ones with contact angle value of 97.05°. The value of IFSS for sized fibers is 51.49 MPa, which is higher than the unsized fibers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Developing an approach to calculate carbon fiber surface energy using molecular simulation and its application to real carbon fibers

Carbon fiber surface energy is calculated using molecular mechanics simulations on the basis of variation in nonbond energy of carbon fiber due to the presence of various functional groups i.e., OH, CO, and COOH. A step-wise methodology is adopted so that optimized graphite models are used to build separate models of carbon fibers for discrete percentages of OH, CO, and COOH to know the effect of each functional group. Eventually, models of three real carbon fibers are developed to know the combined effect of functional groups on the surface energy of carbon fibers.

Formation of a carbon fiber/polyhedral oligomeric silsesquioxane/carbon nanotube hybrid reinforcement and its effect on the interfacial properties of carbon fiber/epoxy composites

A carbon fiber/polyhedral oligomeric silsesquioxane/carbon nanotube (CF–POSS–CNT) hybrid reinforcement was prepared by grafting CNTs onto the carbon fiber surface using octaglycidyldimethylsilyl POSS as the linkage in an attempt to improve the interfacial properties between carbon fibers and an epoxy matrix. X-ray photoelectron spectroscopy, scanning electron microscopy, dynamic contact angle analysis and single fiber tensile testing were performed to characterize the hybrid reinforcements. Interlaminar shear strength (ILSS), impact toughness, dynamic mechanical analysis and force modulation atomic force microscopy were carried out to investigate the interfacial properties of the composites. Experimental results show that POSS and CNTs are grafted uniformly on the fiber surface and significantly increase the fiber surface roughness. The polar functional groups and surface energy of carbon fibers are obviously increased after the modification. Single fiber tensile testing results demonstrate that the functionalization does not lead to any discernable decrease in the fiber tensile strength. Mechanical property test results indicate the ILSS and impact toughness are enhanced. The storage modulus and service temperature increase by 11 GPa and 17 °C, respectively. POSS and CNTs effectively enhance the interfacial adhesion of the composites by improving resin wettability, increasing chemical bonding and mechanical interlocking.

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 plasma and electrochemical treatment on the dispersion and polar components of the surface energy of carbon fibers

1. The method of investigating the surface properties of CF presented here can be used to determine the dispersion and polar components of their surface energy. 2. It was shown that the polar component of the surface energy of fibers is correlated with the shearing strength of an epoxy-based plastic. 3. It was shown that oxidative treatment of the surface of the fibers increases the polar component of their surface energy. 4. XPS showed that the concentration of oxygen on the surface increases by approximately two times with plasma treatment. 5. Based on the results obtained, the method of determining the components of the surface energy is recommended for predicting the surface properties of a broad class of carbon fibers.