Interfacial improvement of carbon fiber-reinforced methylphenylsilicone resin composites with sizing agent containing functionalized carbon nanotubes

A liquid sizing agent containing multiwall carbon nanotubes (MWCNTs) was prepared for carbon fiber (CF) reinforced methylphenylsilicone resin (MPSR) composite applications. In order to improve the dispersion of MWCNTs in the sizing agent and interfacial adhesion between CF and MPSR, MWCNTs and CF were functioned by the chemical modification with tetraethylenepentamine (TEPA) used as a MPSR curing agents. The CF before and after the sizing treatment-reinforced MPSR composites were prepared by a compression molding method. The microstructures, interfacial properties, and impact toughness of CF were systematically investigated. Experimental results revealed that a thin layer of MPSR coating containing functionalized MWCNTs (MWCNT-TEPA) was uniformly grafted onto the surface of CF. The sized CF-reinforced MPSR composite showed simultaneously remarkable enhancement in the interlaminar shear strength and impact toughness. Meanwhile, the tensile strength of CF had no obvious decrease after sizing treatment. In addition, the interfacial reinforcing and toughening mechanisms were also discussed. We believe that the facile and effective method in preparing multifunctional fibers provides a novel interface design strategy of carbon fiber composites for different applications.     

The role of grafting force and surface wettability in interfacial enhancement of carbon nanotube/carbon fiber hierarchical composites

The grafting force of carbon nanotube (CNT) on carbon fiber (CF) and the wettability of CF surface were experimentally studied, where hierarchical CNT/CF reinforcement was prepared using chemical vapor deposition (CVD). Then, their effects on interfacial improvement were experimentally and theoretically investigated. The results show that the CNT/CF grafting force is so strong, more than 5 μN, and CNT/CF attachment can sustain the fracture of the CNTs. This is expected to be contributed to the improvement of interfacial properties. However, the deposited catalyst deteriorates the wettability, which could seriously degrade the interfacial properties. As a result, experimental results from the micro-droplet test show that there is only a 30% increase in the interfacial shear strength of hierarchical CNT/CF reinforced composite comparing with that of as-received CF reinforced composite. An analytical model was developed to predict the effects of CNT/CF grafting force on interfacial improvement, and the predicted results are in agreement with the experimental one.     

炭纤维表面处理对CF／PMR—15复合材料力学性能的影响

研究了炭纤维表面不同处理方法对复合材料力学性能的影响,采用等离子体和等离子体接枝技术对炭纤维表面进行处理后,CF／PMR－15复合材料的界面剪切强度与层间剪切强度均有所提高,随着界面状态的改善,界面剪切强度提高的幅度比层间剪切强度提高的大,本文为指导炭纤维的表面处理,评价处理效果,进一步预报复合材料的宏观性能打下了基础。     

Effect of surface treatment on the tribological performance of carbon fiber reinforced thermoplastic polyimide composites

The effect of rare earth solution (RES) surface treatment of carbon fibers (CFs) on the tensile strength and tribological properties of CF‐reinforced polyimide (CF/PI) composite was investigated. Experimental results revealed that the tensile strength of RES‐treated CFs reinforced PI composite was improved by about 19% compared with that of untreated composite, while 7% improvement was achieved by air oxidation. Compared with the untreated and air‐oxidated CF/PI composite, the RES‐treated composite had the lowest friction coefficient and specific wear rate under given applied load and reciprocating sliding frequency. RES treatment effectively improved the interfacial adhesion between CFs and PI. The strong interfacial adhesion of the composite made CFs not easy to detach from the PI matrix and prevented the rubbing‐off of PI, and accordingly improved the friction and wear properties of the composite. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Improvement of carbon fiber/PEEK hybrid fabric composites using plasma treatment

A carbon fiber (CF)/polyetheretherketone (PEEK) composite was manufactured using hybrid fabrics composed of CF and PEEK fiber. The fiber/matrix interface was modified by low temperature oxygen plasma treatment. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform attenuated total reflection infrared spectroscopy (FTIR-ATR) were used to relate the roughness and the functionality of the CF surface with the interfacial adhesion strength of the CF/PEEK composite. Scanning electron micrographs showed that plasma treatment increased the roughness of the CF surface up to 3 min of plasma treatment time; and prolonged treatment resulted in overall smoothing. XPS results confirmed that increasing treatment time marginally increased surface functionality: treatment for more than 5 min decreased the surface functionality by removing the active site of the CF surface. In addition, flexural strength and interlaminarshear strength (ILSS) of the CF/PEEK composite were measured. Their maximum values were observed at 3 min of plasma treatment time as a result of surface roughening by plasma etching. The SEM results were correlated with mechanical properties of the CF/PEEK composite.     

Interfacial adhesion of plasma‐treated carbon fiber/poly(phthalazinone ether sulfone ketone) composite

Interfacial adhesion between fiber and matrix has a strong influence on composite mechanical performance. To exploit the reinforcement potential of the fibers in advance composite, it is necessary to reach a deeper understanding on the relation between fiber surface treatment and interfacial adhesion. In this study, air plasma was applied to modify carbon fiber (CF) surface, and the capability of plasma grafting for improving the interfacial adhesion in CF/thermoplastic composite was discussed and also the mechanism for composite interfacial adhesion was analyzed. Results indicated that air plasma treatment was capable of increasing surface roughness as well as introducing surface polar groups onto CF; both chemical bonding and mechanical interaction were efficient in enhancements of interlaminate shear strength of CF/PPESK composite, while mechanical interaction has a dominant effect on composite interfacial adhesion than chemical bonding interaction. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Self-healing interfaces of poly(methyl methacrylate) reinforced with carbon fibers decorated with carbon quantum dots

Fiber-polymer matrix interfacial debonding is often observed when mechanical loads are applied to fiber reinforced polymer composites. These defects usually end-up leading to a catastrophic fracture of the composites. In this work, carbon quantum dots (CDs) were incorporated on the surface of carbon fibers (CF), and poly(methyl methacrylate) (PMMA) composites with these modified fibers were able to restore their original properties after been previously damaged. To this end, CDs were synthesized and used to decorate the surface of CF. These decorated CF were then incorporated into PMMA by using a high intensity mixer. The prepared composites were submitted to dynamic mechanical, three-point bending and self-healing tests. Fluorescent CDs with diameters of 10 nm and functional groups, such as amine and carboxylic groups were successfully synthesized by the microwave pyrolysis method. The deposition of CDs on the surface of CF was evaluated and quantified by UV–vis spectroscopy and 1.2 wt.% of CDs on CF was determined. Composites with different surface treatments (including the presence of CD) did not show significant differences in strength, stiffness and damping, suggesting that the surface treatments on CF did not lead to major changes in the degree of interfacial interaction. Self-healing tests showed that damaged composites with CD decorated CF were able to restore their original properties, while no self-healing effect was noted in composites with no CD on CF. The observed self-healing behavior between PMMA and CF decorated with CD is due to the interactions between chemical groups on the surface of the CD and PMMA. Thus, damages related to fiber-matrix interfacial detachments can be repaired through reversible interactions based on CD.     

Effects of chain lengths,molecular orientation,and functional groups of thiols adsorbed onto CF surface on interfacial properties of CF/epoxy composites

In this article, a new treatment method based on molecular self‐assembly on carbon fiber (CF) surface was proposed for obtaining a controlled interface between CF and epoxy matrix in composite system. To form the controlled interfacial region, the surfaces of CF were first metallized by electroless Ag plating, then were reacted with a series of thiols (alkanethiols, aromatic thiol, and heterocyclic thiol) to form self‐assembly (SA) films, which further reacted with epoxy resin to generate a strong adhesion interface. The structure and composition of untreated and treated CF surface were investigated by surface‐enhanced Raman scattering spectroscopy (SERS) and X‐ray photoelectron spectroscopy (XPS), respectively. SERS study showed that thiols chemisorbed on Ag‐plated CF in the form of thiolate species via the strong S? Ag coordinative bond. Moreover, adsorbate orientation of thiols SA films on Ag‐plated CF surfaces was revealed on the basis of SERS selection rules. The XPS study further confirmed the well organized alignment and the chemisorption of thiols. To understand the interfacial adhesion mechanism, the interfacial shear strength of CF/epoxy microcomposites was evaluated by the microbond technique. The results showed that among the parameters such as chain lengths, molecular orientation, and types of functional groups, the chemical nature of functional groups is most important for the improvement of interfacial properties in CF/epoxy composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effect of various methods of pre-treatment of carbon fibers on the mechanical properties of PIP-based ceramics/carbon composites

The purpose of the work was to determine the conditions of CF preparation to obtain carbide composites with favorable mechanical response. The relationships between the interfacial properties of fiber/polymethylsiloxane composite, and mechanical properties of the resulting fiber/carbide composites were investigated. The CF/resin interfacial strength was modified by oxidation of CF surface with nitric acid, silanization, and depositing CNT or a pyrolytic carbon layer (PyC). The study of composite interphases (ILSS and SEM) and surface tests of the modified CF (XPS, FT-IR, wettability measurements) showed different nature of the bonding occurring at the fiber/resin and fiber/ceramics boundary. The CF silanization significantly improved the ILSS between CFs and resin by 38.5%, while reduced flexural properties of carbide composites. The most promising treatment method of CF for PIP-based ceramic composites was modification with PyC, which provided 2 times higher ILSS, 1.5 times higher flexural strength and improved work to fracture (WF) as compared to unmodified CF.     

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.     

空心玻璃微珠对碳纤维增强聚丙烯性能的影响研究

以碳纤维(CF)增强聚丙烯(PP)作为基础材料,添加空心玻璃微珠(GB)对其进行共混改性,研究GB的加入量对其流动性能和力学性能的影响。转矩流变性能、拉伸性能、冲击性能和微观形貌的分析与研究结果表明,GB对PP/CF复合材料具有增强增韧的作用。     

沸水对PI/CF复合材料界面作用机理的研究

研究了聚酰亚胺(PI)／碳纤维(CF)复合材料界面在沸水中的稳定性。结果表明,经沸水浸泡后的复合材料层间剪切强度和界面剪切强度均有所提高,且随水煮时间的延长而增大;试样断面观察表明,水没有对复合材料界面产生破坏作用,力学性能的变化与基体／纤维界面粘结的湿热稳定性有直接关系;沸水对界面的作用机理是,在PI／CF复合材料的界面区,树脂的水解使氢键的数量增加,形成了防水层,阻碍了水沿界面的侵入,同时水松驰了界面局部应力。     

The improved interface performance between carbon fiber and poly(ether-ether-ketone) by sulfonated polyether sulfone (s-PSF) sizing agent with different sulfonation degree

The effects of sulfonated polyether sulfone (s-PSF) with different sulfonation degrees on the interfacial properties of carbon fiber (CF)/poly(ether-ether-ketone) (PEEK) composites were investigated systematically. The performance of the modified CF and the corresponding CF/PEEK composites and was tested and characterized. Test results show that the CF surface polarity increases, the surface contact angle decreases, and the surface free energy increases with the increase in the s-PSF sulfonation degree. Scanning electron microscopy analysis shows that the increase in the sulfonation degree of s-PSF is beneficial to improve the interface between CF and PEEK. This condition can be ascribed to the hydrogen bonding force between the s-PSF sulfonic acid group and the polar functional group on the surface of the modified CF and the compatibility between s-PSF and PEEK. In terms of physical properties, the thermal and mechanical properties of CF/PEEK composite are improved with the increase in s-PSF sulfonation degree. The interlaminar shear strength, flexural strength, and modulus of CF/PEEK composites increase by 60.16%, 30.27%, and 19.30%, respectively.     

粘胶基碳纤维连续式电化学氧化表面处理(Ⅱ)碳纤维增强复合材料的界面

本文用短支梁三点弯曲法及Fragment法测定了连续式电氧化处理粘胶基碳纤维与酚醛树脂及环氧树脂复合材料界面粘合性 ,并用SEM观察了其界面的形貌。结果表明 :在本试验范围内经电化学氧化处理可以使粘胶基碳纤维 /酚醛树脂复合材料界面的粘合强度提高25 % ,而粘胶基碳纤维 /环氧树脂复合材料界面的粘合强度可提高100 %。这可能是由于环氧树脂可与碳纤维表面的官能团形成化学键的原因。     

Mechanical,Thermal and Electrical Resisitivity Properties of Thermoplastic Composites Filled with Carbon Fibers and Carbon Particles

Composites consisting of carbon fibers (CF) and carbon particles (CP) in polypropylene (PP) matrix were melt-compounded. Composites were analyzed for their mechanical, electrical and thermal properties. Results indicate that the addition of these fillers improved the mechanical properties of the composites. Thermal conductivity was enhanced as the concentration of fillers was increased. Carbon fibers render the composites electrically conductive so we observed a percolation threshold near 10 wt.% of CF for PP/CF (PP and CF composite) and near 25 wt.% of CP for PP/CP (PP and carbon particle composite). All the results indicated that carbon fibers are more effective in improving the properties as compare to the carbon particles.     

Improved interfacial adhesion in carbon fiber/poly (ether ether ketone) composites with the sulfonated poly (ether ether ketone) sizing treatment

A water-soluble sulfonated poly (ether ether ketone) (SPEEK) sizing agent is prepared and applied to improve the interfacial adhesion of carbon fiber/poly (ether ether ketone) (CF/PEEK) composites. The surface morphology, surface roughness, surface chemistries, and surface free energy of SPEEK sized CF are obtained to understand the sizing effect. The results reveal the increased surface free energy and surface roughness of SPEEK sized CF. In addition, a chemical reaction between the CF surface and sizing layer is proved based on the results of XPS, IR, and ¹H NMR. The interfacial structure of CF/PEEK composites is further ascertained by AFM and the appearance of gradient interface could be verified for SPEEK sized CF/PEEK composites. The formation of the gradient interface is due to the chemical reaction between the CF and sizing agent as well as the improved compatibility between the sized CF and matrix, which benefits the improvement of interfacial adhesion.     

Continuous growth of carbon nanotubes on the surface of carbon fibers for enhanced electromagnetic wave absorption properties

As electromagnetic wave (EMW) pollution has become a serious problem in daily life, lightweight, efficient, and mass-produced EMW-absorbing materials are urgently needed. Herein, we developed a novel method for the continuous growth of carbon nanotubes (CNTs) on the surface of polyacrylonitrile (PAN)-based carbon fibers (CFs) by chemical vapor deposition (CVD), which can be applied to mass production. The obtained CF/CNT composites demonstrate outstanding EMW absorption capability, exhibiting a -58.75 dB reflection loss (RL) at a thickness of 1.54 mm. An effective absorption bandwidth (RL < -10 dB) of 4.24 GHz (13.76–18.00 GHz) was achieved at a thickness as low as 1.25 mm, which almost covers the entire Ku band. The excellent EMW-absorbing performance can be attributed to the 3D conductive network constructed by the CNT forest, which effectively promotes multiple reflections and scattering, and further favors dipole and interface polarizations. The mechanical properties of CF, CF-electrochemical anodic oxidation (EAO), and CF/CNT composites were examined, the results showed that the single-filament tensile strength of CF/CNT@0.07 and CF/CNT@0.09 was effectively improved. Our work suggests that the novel CF/CNT composite is a promising material for EMW absorption and strength enhancement owing to its light weight, high strength, low thickness, and good scale-up ability.     

长碳纤维／聚丙烯复合材料加工工艺和性能的研究

本文利用单螺杆挤出机，采用电缆包覆式工艺，进行聚丙烯树脂包覆长碳纤维，然后再二次造粒，制备出长碳纤维／聚丙烯合粒料，对此复合材料和原ＰＰ树脂的性能测试结果发现，因碳纤维表面未经处理，致使复合材料的拉伸强度，伸长率，缺口冲击强度较原ＰＰ树脂有一定程度地下降，而此复合材料的导电性却大大提高，结合其断口和横截面和电子扫描电镜照片，讨论了复合材料力学性能下降和电学性能提高的机理。     

Effects of polyhedral oligomeric silsesquioxane coatings on the interface and impact properties of carbon‐fiber/polyarylacetylene composites

Two kinds of polyhedral oligomeric silsesquioxane (POSS) coatings were used for the modification of the interface in carbon fiber (CF) reinforced polyarylacetylene (PAA) matrix composites. The effects of the organic–inorganic hybrid POSS coatings on the properties of the composites were studied with short‐beam‐bending, microdebonding, and impact tests. The interlaminar shear strength and interfacial shear strength showed that the POSS coatings resulted in an interfacial property improvement for the CF/PAA composites in comparison with the untreated ones. The impact‐test results implied that the impact properties of the POSS‐coating‐treated composites were improved. The stiffness of the interface created by the POSS coatings was larger than that of the fiber and matrix in the CF/PAA composites according to the force‐modulation‐mode atomic force microscopy test results. The rigid POSS interlayer in the composites enhanced the interfacial mechanical properties with a simultaneous improvement of the impact properties; this was an interesting phenomenon in the composite‐interface modification. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5202–5211, 2006     

短碳纤维增强聚丙烯复合材料性能的研究

本文研究了单螺杆挤出机加工短碳纤维增强聚丙烯复合材料（ＣＦＲＰＰ）的性能。结果表明，经表面处理的短碳纤维与ＰＰ复合，得到的材料其拉伸强度、冲击强度和热变形温度有明显提高，成型收缩率显著减小、电性能与半导体相近。本文还结合拉伸断面的电镜照片，比较分析了表面处理前后短碳纤维增强ＰＰ复合材料力学性能的变化。