Enhanced interfacial strength and mechanical properties of carbon fiber composites by introducing functionalized silica nanoparticles into the interface

Introducing nanoparticles onto the surface of carbon fibers (CFs) is a useful method for enhancing the quality of fiber-matrix interface. In this work, a liquid sizing agent containing functionalized silica nanoparticles (SiO₂) was well prepared to improve interfacial strength and mechanical properties of composites. In order to enhance the dispersion of SiO₂ nanoparticles in sizing agent, SiO₂ nanoparticles were chemically grafted with 3-aminopropyltriethoxysilane (APS), and then silanized silica (SiO₂-APS) was introduced into the interphase by a conventional sizing process as well. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the successful preparation of SiO₂-APS. Scanning electron microscopy (SEM) showed that a uniform distribution of SiO₂-APS on the fiber surface and the increased surface roughness. The sized fibers (CF/SiO₂-APS) exhibited a high surface free energy and good wettability based on a dynamic contact angle testing. Interfacial microstructure and mechanical properties of untreated and sized CFs composites were investigated. Simultaneous enhancements of interlaminar shear strength (ILSS) and impact toughness of CF/SiO₂-APS composites were achieved, increasing 44.79% in ILSS and 31.53% in impact toughness compared to those of untreated composites. Moreover, flexural strength and modulus of composites increased by 32.22 and 50.0% according to flexural test. In addition, the hydrothermal aging resistance of CF/SiO₂-APS composites has been improved significantly owing to the introduced Si-O-Si bonds at the interface.     

Mechanical properties of carbon fiber reinforced bisphenol A dicyanate ester composites modified with multiwalled carbon nanotubes

A novel electrophoretic deposition (EPD) method was employed for grafting multiwalled carbon nanotubes (MWCNTs) on carbon fibers, which, after impregnation with bisphenol A dicyanate ester (BADCy), synergistically reinforced BADCy matrix composites (CNT‐C/BADCy). The effect of MWCNT presence on the mechanical properties of the composites was investigated. Composite tensile strength increased by 45.2% for an EPD duration of 2 min, while flexural strength exhibited a decreasing trend with EPD duration. Optical microscopy revealed that the existence of MWCNTs enhanced the fiber‐matrix interface while a large number of CNTs were observed to have pulled‐out from the matrix, a finding which explained the observed tensile strength increase in terms of energy dissipation by the specific toughening mechanism. The flexural strength decrease of the composites with CNTs as compared to specimens without nanotubes was found linked to the increased stress concentration in the BADCy matrix due to tube presence which weakens the adhesion between carbon fabrics. In a word, carbon nanotubes will enhance the micro interface and weaken the macro interface of the composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45100.     

碳/碳复合材料力学性能的研究进展

本文综述了碳/碳复合材料力学性能的研究进展,包括碳纤维、基体炭、界面性能、制备工艺及工艺参数等对碳/碳复合材料力学性能的影响。同时简单介绍了当今单向碳/碳复合材料力学性能的表征手段。希望对碳/碳复合材料力学性能的研究及应用提供帮助。     

The preparation of emulsion type sizing agent for carbon fiber and the properties of carbon fiber/vinyl ester resin composites

Vinyl ester resin emulsion type sizing agent (HMSA‐1) was synthesized by phase inversion emulsification method. Centrifugal sedimentation analysis, particle size analysis, Fourier transforms infrared spectroscopy (FTIR), and gel permeation chromatography were used to characterize HMSA‐1 and Japanese commercial sizing agents (JSA‐1 and JSA‐2). Meanwhile, abrasion resistance, fluffs and breakage, stiffness, scanning electron microscope (SEM) were used to analyze the workability in later process of carbon fiber and surface morphology. The results showed that HMSA‐1 could significantly improve handling characteristics of carbon fiber. SEM micrographs demonstrated that the sized carbon fiber had smooth surface. HMSA‐1 had better compatibility with vinyl ester resin. The interlaminar shear strength (ILSS) of HMSA‐1 sized carbon fiber/vinyl ester resin composite reached the maximum value of 45.96 MPa. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical properties of carbon fiber composites modified with graphene oxide in the interphase

The surface topographies of carbon fibers treated by sizing agents with different graphene oxide (GO) content were investigated by scanning electron microscopy. The surface elements compositions of carbon fibers were determined by X‐ray photoelectron spectrometer. The interfacial properties of composites were studied by interfacial shear strength. The thermo‐mechanical properties of two typical specimens (CF‐G0 and CF‐G1 composites) were investigated by dynamic mechanical thermal analysis. The results showed the introduction of GO sheets on carbon fibers surfaces effectively improved the mechanical properties of carbon fibers/epoxy composites. POLYM. COMPOS., 38:2425–2432, 2017. © 2016 Society of Plastics Engineers     

Improved interfacial adhesion in carbon fiber/epoxy composites through a waterborne epoxy resin sizing agent

A series of self‐emulsified waterborne epoxy resin (WEP) emulsions were used as surface sizing for carbon fibers (CFs) to improve the interfacial adhesion between the CF and epoxy matrix. In this work, the hydrogenated bisphenol‐A epoxy resin (HBPAE) was modified by polyethylene glycol (PEG) with molecular weights of 400, 800, 1000, 1500, 2000, 4000, and 6000 g/mol. The properties of the WEP emulsion were examined by Fourier transform infrared spectroscopy, dynamic light scattering, and transmission electron microscopy. The surface characteristics of sized CFs were evaluated using scanning electron microscopy, atomic force microscopy, and X‐ray photoelectron spectroscopy. Afterwards, CF/EP composites were prepared and their fracture surface and interlaminar shear strength (ILSS) were examined. The results indicated that PEG2000 modified HBPAE sizing had the optimum emulsion stability and film‐forming ability. Meanwhile, the results also demonstrated that a continuous and uniform sizing layer was formed on the surface of CFs and the surface sizing was excellent in improving the chemical activity of CFs. Compared with unsized CFs, the O1s/C1s composition ratio was observed to increase from 11.51% to 33.17% and the ILSS of CF/EP composites increased from 81.2 to 89.7 MPa, exhibiting better mechanical property than that of commercial Takemoto S64 sized CFs. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44757.     

气相纳米SiO_2改性三聚氰胺纤维性能研究

采用原位聚合的方法,以偶联剂KH-570进行表面改性的气相纳米SiO_2与三聚氰胺纺丝原液进行混合,经干法纺丝,制得气相纳米SiO_2粒子改性三聚氰胺纤维(MF),对改性MF的结构与性能进行了表征。结果表明:MF表面光滑,不含有气泡,经过KH-570改性的气相纳米SiO_2在纤维的表面分布较均匀,起到消光作用,纤维直径小于100μm;由于气相纳米SiO_2的加入,MF断裂强度有所减小,断裂伸长率提高达6.05%,纤维耐热性能没有较大变化,其热分解温度为390℃。     

短碳纤维增强铝基复合材料

通过化学镀再电镀的方法,在碳纤维表面镀上Cu镀层,制备C/Cu复合丝,并在硼酸的保护下,利用非真空条件下的液态机械搅拌法制备短碳纤维增强铝基复合材料,研究了碳纤维在复合材料中的分散程度,铜镀层存在状态及C/Al复合材料的拉伸性能.实验结果表明：在硼酸存在下,大大降低了铜的氧化程度,碳纤维分散均匀且没有损伤,少量硼酸的加入,对复合材料的力学性能没有影响,该复合材料的抗拉强度随碳纤维含量的增加而增加,其抗拉强度较基体材料提高50%以上,但塑性指标却明显下降.     

Mechanical properties and ablation resistance of HfC nanowire modified carbon/carbon composites

Hafnium carbide nanowires (HfCnws) were in-situ grown in carbon/carbon (C/C) composites, and subsquently the preforms were densified by isothermal chemical vapor infiltration to obtain HfCnws modified carbon/carbon (HfCnws-C/C) composites. Morphology and microstructure of HfCnws were examined, and the effect of HfCnws on the mechanical property and ablation resistance of C/C composites were also investigated. Results show that introducing HfCnws refined the grain size of pyrolytic carbon (PyC). The out-of-plane compression, interlaminar shear and flexual strength of HfCnws-C/C composites increased by 120.80%, 45.60% and 94.65%, respectively compared with pure C/C, and the HfCnws-C/C shows good ablation resistance under oxy-acetylene flame ablation.     

Mechanical and thermal properties of polypropylene/modified basalt fabric composites

Basalt fabric (BF) was first treated with silane coupling agent KH550, modified basalt fabric (MBF) was obtained. Then MBF were molded with polypropylene (PP) matrix, and polypropylene/modified basalt fabrics (PP/MBF) composites were obtained. The influence of concentration and treating time of KH550 on MBF were characterized by hydrophilicity and lipophilicity. The tensile strength and morphology of basalt fabric were tested by single filament strength tester and scanning electron microscopy. The mechanical properties of composites were measured with electronic universal testing machine and impact testing machine, and the thermal properties were tested by thermogravimetric analysis and dynamic mechanical analysis. The results showed that the lipophilicity of MBF is improved significantly by KH550 while the tensile is nearly damaged. The mechanical properties of composites are larger than that of pure PP, among which the impact property was improved the most, showing 194.12% enhancement. The thermal stability and dynamic viscoelasticity were better than pure PP; furthermore, the concentration of KH550 virtually had no effect on the thermal stability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42504.     

Mechanical and morphological properties of carbon fiber reinforced–modified epoxy composites

Epoxy, prepared through aminomethyl 3,5,5‐trimethylcyclohexylamine hardening of diglycidylether of bisphenol‐A (DGEBA) prepolymer, toughened with polycarbonate (PC) in different proportions, and reinforced with carbon fiber, was investigated by differential scanning calorimetry, tensile and interlaminar shear strength testing, and scanning electron microscopy (SEM). A single glass transition temperature was found in all compositions of the epoxy/PC blend system. The tensile properties of the blend were found to be better than that of the pure epoxy matrix. They increased with PC content up to 10%, beyond which they decreased. The influence of carbon fiber orientation on the mechanical properties of the composites was studied, where the fiber content was kept constant at 68 wt %. Composites with 45° fiber orientation were found to have very weak mechanical properties, and the mechanical properties of the blend matrix composites were found to be better than those of the pure epoxy matrix composites. The fracture and surface morphologies of the composite samples were characterized by SEM. Good bonding was observed between the fiber and matrix for the blend matrix composites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3529–3536, 2006     

Fabrication and properties of lightweight SiOC modified carbon-bonded carbon fiber composites

SiOC modified carbon-bonded carbon fiber composites (CBCFs) with densities of 0.38, 0.61, 0.94 g cm⁻³ were prepared by precursor infiltration and pyrolysis method using dimethoxydimethylsilane and methyltrimethoxysilane as precursors. The densification behavior was investigated by analyzing the microstructure of CBCF-SiOC (CS) composites with different densities. The mechanical properties and oxidation resistance of the CS composites were studied. Results indicate that the CS composites with the density of 0.94 g cm⁻³ exhibit better mechanical and anti-oxidation properties.     

Structure and properties of UHMWPE fiber/carbon fiber hybrid composites

Ultrahigh molecular weight polyethylene (UHMWPE) fiber/carbon fiber hybrid composites were prepared by inner‐laminar and interlaminar hybrid way. The mechanical properties, dynamic mechanical analysis (DMA), and morphologies of the composites were investigated and compared with each other. The results show that the hybrid way was the major factor to affect mechanical and thermal properties of hybrid composites. The resultant properties of inner‐laminar hybrid composite were better than that of interlaminar hybrid composite. The bending strength, compressive strength, and interlaminar shear strength of hybrid composites increased with an increase in carbon fiber content. The impact strength of inner‐laminar hybrid composite was the largest (423.3 kJ/m²) for the UHMWPE fiber content at 43 wt % to carbon fiber. The results show that the storage modulus (E′), dissipation factor (tan δ), and loss modulus (E″) of the inner‐laminar hybrid composite shift toward high temperature remarkably. The results also indicate that the high‐performance composite with high strength and heat resistance may be prepared by fibers' hybrid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1880–1884, 2006     

Mechanical properties of biorenewable fiber/plastic composites

Plastic fiber composites, consisting of polypropylene (PP) or polyethylene (PE), and pinewood, big blue stem (BBS), soybean hulls, or distillers dried grain and solubles (DDGS), were prepared by extrusion. Young's modulus, tensile and flexural strengths, melt flow, shrinkage, and impact energy, with respect to the type, amount, and size of fiber on composites, were evaluated. Young's moduli under tensile load of wood, BBS, and soybean‐hull fiber composites, compared with those of pure plastic controls, were either comparable or higher. Tensile strength significantly decreased for all the PP/fiber composites when compared with that of the control. Strength of BBS fiber composites was higher than or comparable to that of wood. When natural fibers were added there was a significant decrease in the melt flow index for both plastic/fiber composites. There was no significant difference in the shrinkage of all fiber/plastic composites compared to that of controls. BBS/PE plastic composites resulted in higher notched impact strength than that of wood or soybean‐hull fiber composites. There was significant reduction in the unnotched impact strength compared to that of controls. BBS has the potential to be used as reinforcing materials for low‐cost composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2484–2493, 2004     

Mechanical and rheological properties of polypropylene/bentonite composites with stearic acid as an interface modifier

In this study, we present a study of polypropylene/bentonite composites where stearic acid was used as both a surface and interface modifier during the compounding of composites. The concentration of bentonite was 1.5, 2.5, 5.0, and 10 parts per hundred. The composites were characterized by impact resistance and tensile tests, rheological analysis, the dispersion state of the filler observed by optical microscopy, and interaction between bentonite and stearic acid, as analyzed by Fourier transform infrared spectroscopy. No chemical interaction was found between bentonite and stearic acid. Composites with modified bentonite and stearic acid used as interface modifiers increased the elongation at break; these samples also showed better dispersion of the filler in comparison with the other compounds. In addition, stearic acid acted as a lubricant, favoring the interaction of the polymer with the filler and decreasing the viscosity of the compounds. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42264.     

Effect of carbon nanotube purification on the electrical and mechanical properties of poly(ethylene terephthalate) composites with carbon nanotubes in low concentration

Surface properties of carbon nanotubes (CNTs) were altered by purification with nitric acid, sulfuric acid, ammonium hydroxide, and hydrogen peroxide. As‐received and purified CNT‐based conductive poly (ethylene terephthalate) composites were prepared with a twin‐screw extruder. The effects of CNT purification on the surface properties of the CNTs and on the morphology and electrical and mechanical properties of CNT‐based composites were investigated. Surface energy measurements showed that the acidic component of the surface energies of the CNTs increased after purification. According to Fourier transform infrared (FTIR) spectroscopy, the purification resulted in the formation of oxygen‐containing functional groups on the surfaces of the CNTs. Electron spectroscopy for chemical analysis results indicate the removal of the metallic catalyst residues and an increase in the oxygen content of the CNT surfaces as a result of the purification procedure. X‐ray diffraction analyses revealed a change in the crystalline structure of the CNTs after purification. All of the composites prepared with the purified CNTs had higher electrical resistivities and tensile and impact strength values than the composites based on the as‐received CNTs because of the functional groups and defect sites formed on the surfaces of the CNTs during purification. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Study on the mechanical properties and microstructure of high-performance carbon fiber/epoxy composites

A high-toughness epoxy has been prepared using carboxyl-terminated butadiene acrylonitrile (CTBN) as a toughening agent to modify the AG-80 epoxy resin. High-performance carbon fiber/epoxy (CF/EP) composites are fabricated using the CTBN-toughened epoxy resin as the matrix and two types of CF, namely, T800SC and T800HB, as reinforcement. The mechanical properties of the matrix, surface properties of the CFs, tensile properties, and fracture morphologies of the composites are systematically investigated to elucidate the key factors influencing interfacial bonding in high-performance CF/EP composites. The results reveal that the most significant improvement in toughness is achieved when the CTBN content is 6.90 wt.% in the epoxy resin. Owing to the high content of polar functional groups and excellent surface wettability of T800SC, the T800SC/EP composite exhibits superior mechanical properties compared with the T800HB/EP composite.     

Mechanical and tribological properties of glass–epoxy composites with and without graphite particulate filler

The objectives of this research article is to evaluate the mechanical and tribological properties of glass‐fiber‐reinforced epoxy (G–E) composites with and without graphite particulate filler. The laminates were fabricated by a dry hand layup technique. The mechanical properties, including tensile strength, tensile modulus, elongation at break, and surface hardness, were investigated in accordance with ASTM standards. From the experimental investigation, we found that the tensile strength and dimensional stability of the G–E composite increased with increasing graphite content. The effect of filler content (0–7.5 wt %) and sliding distance on the friction and wear behavior of the graphite‐filled G–E composite systems were studied. Also, conventional weighing, determination of the coefficient of friction, and examination of the worn surface morphological features by scanning electron microscopy (SEM) were done. A marginal increase in the coefficient of friction with sliding distance for the unfilled composites was noticed, but a slight reduction was noticed for the graphite‐filled composites. The 7.5% graphite‐filled G–E composite showed a lower friction coefficient for the sliding distances used. The wear loss of the composites decreased with increasing weight fraction of graphite filler and increased with increasing sliding distance. Failure mechanisms of the worn surfaces of the filled composites were established with SEM. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2472–2480, 2007