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.     

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 nanotube/carbon fiber reinforced thermoplastic polymer composite

Carbon nanotube (CNT)/carbon fiber (CF) hybrid fiber was fabricated by sizing unsized CF tow with a sizing agent containing CNT. The hybrid fiber was used to reinforce a thermoplastic polymer to prepare multiscale composite. The mechanical properties of the multiscale composite were characterized. Compared with the base composite (traditional commercial CF), the multiscale composite reinforced by the CNT/CF hybrid fiber shows increases in interlaminar shear strength (ILSS) and impact toughness. Laminate containing CNTs showed a 115.4% increase in ILSS and 27.0% increase in impact toughness. The reinforcing mechanism was also discussed by observing the impact fracture morphology. POLYM. COMPOS., 38:2001–2008, 2017. © 2015 Society of Plastics Engineers     

Mechanical properties of carbon fiber composites modified with nano-SiO2 in the interphase

The performance of carbon fibers-reinforced composites is dependent to a great extent on the properties of fiber–matrix interface. To improve the interfacial properties in carbon fibers/epoxy composites, nano-SiO₂ particles were introduced to the surface of carbon fibers by sizing treatment. Atomic force microscope (AFM) results showed that nano-SiO₂ particles had been introduced on the surface of carbon fibers and increase the surface roughness of carbon fibers. X-ray photoelectron spectroscopy (XPS) showed that nano-SiO₂ particles increased the content of oxygen-containing groups on carbon fibers surface. Single fiber pull-out test (IFSS) and short-beam bending test (ILSS) results showed that the IFSS and ILSS of carbon fibers/epoxy composites could obtain 30.8 and 10.6% improvement compared with the composites without nano-SiO₂, respectively, when the nano-SiO₂ content was 1 wt % in sizing agents. Impact test of carbon fibers/epoxy composites treated by nano-SiO₂ containing sizing showed higher absorption energy than that of carbon fibers/epoxy composites treated by sizing agent without nano-SiO₂. Scanning electron microscopy (SEM) of impact fracture surface showed that the interfacial adhesion between fibers and matrix was improved after nano-SiO₂-modified sizing treatment. Dynamic mechanical thermal analysis (DMTA) showed that the introduction of nano-SiO₂ to carbon fibers surface effectively improved the storage modulus of carbon fibers/epoxy.     

Effect of sizing on interfacial adhesion of commercial high strength carbon fiber‐reinforced resin composites

The influence of sizing agent on interfacial shear strength (IFSS) of carbon fiber/epoxy (CF/EP) and carbon fiber/bismaleimide (CF/BMI) was investigated. Since sizing agent can alter physicochemical properties of CF surface, possible affecting factors, including sizing reactivity, chemical reactions between sizing and resin, wettability of fiber with resin, fiber surface roughness, and chemical composition of fiber surface, were discussed. It is found that contact angle of fiber with resin and sufficient chemical reactions between sizing and resin reveal strong correlation with the interfacial adhesion of CF/EP and CF/BMI, while the effect of surface roughness and the amount of oxygen on the fiber surface are relatively weak. Due to EP type of the composition, the sizing agent tends to improve the wettability of CF with EP, while goes against for the fiber with BMI. POLYM. COMPOS., 254–261, 2016. © 2014 Society of Plastics Engineers     

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.     

Mechanical properties of carbon nanofiber/fiber-reinforced hierarchical polymer composites manufactured with multiscale-reinforcement fabrics

Hierarchical polymer composites – defined as carbon nanofiber/fiber-reinforced polymer composites – were manufactured using multiscale-reinforcement fabrics (MRFs) and they were characterized for their mechanical properties. The MRFs were fabricated by electrophoretic deposition of carboxylic acid- or amine-functionalized carbon nanofibers (CNFs) on the surface of sized or unsized carbon fiber layers. Compared to the base composite (not containing CNFs), the hierarchical composites containing the functionalized CNFs showed an increase in interlaminar shear strength (ILSS) and compressive strength. Panels containing amine-functionalized CNFs had the highest increase in properties: 12% in ILSS and 13% in compressive strength. The reinforcement mechanism was also investigated with emphasis placed on the fiber/matrix interface and the load transfer between matrix, CNFs, and carbon fiber.     

聚丙烯腈基碳纤维用环氧树脂上浆剂的比较

用两种环氧树脂上浆剂对国产聚丙烯腈基碳纤维进行上浆,测试和比较了两种环氧树脂上浆剂对聚丙烯腈(PAN)基碳纤维耐磨性、与水接触角、表面能等性能以及拉伸强度、伸长率、层间剪切强度(ILSS)等力学性能的影响。上浆剂中主体成分环氧树脂相对分子质量不是影响碳纤维层间剪切强度的决定性因素。     

Influence of oxygen plasma treatment parameters on the properties of carbon fiber

This study is focused on the impact of oxygen plasma treatment on properties of carbon fibers and interfacial adhesion behavior between the carbon fibers and epoxy resin. The influences of the main parameters of plasma treatment process, including duration, power, and flow rate of oxygen gas were studied in detail using interlaminar shear strength (ILSS) of carbon fiber composites. The ILSS of composites made of carbon fibers treated by oxygen plasma for 1 min, at power of 125 W, and oxygen flow rate of 100 sccm presented a maximum increase of 28% compared to composites made of untreated carbon fibers. Furthermore, carbon fibers were characterized by scanning electron microscopy (SEM), tensile strength test, attenuated total reflectance Fourier transform infrared (ATR-FTIR), and Raman spectroscopy analyses. It was found that the concentration of reactive functional groups on the fiber surface was increased after the plasma modification, as well the surface roughness, which finally improved the interfacial adhesion between carbon fibers and epoxy resin. However, high power and long exposure times could partly damage the surface of carbon fibers and decrease the tensile strength of filaments and ILSS of treated fiber composites.     

Improving delamination resistance of carbon fiber reinforced polymeric composite by interface engineering using carbonaceous nanofillers through electrophoretic deposition: An assessment at different in-service temperatures

In this article, modification of carbon fiber surface by carbon based nanofillers (multi-walled carbon nanotubes [CNT], carbon nanofibers, and multi-layered graphene) has been achieved by electrophoretic deposition technique to improve its interfacial bonding with epoxy matrix, with a target to improve the mechanical performance of carbon fiber reinforced polymer composites. Flexural and short beam shear properties of the composites were studied at extreme temperature conditions; in-situ cryo, room and elevated temperature (−196, 30, and 120°C respectively). Laminate reinforced with CNT grafted carbon fibers exhibited highest delamination resistance with maximum improvement in flexural strength as well as in inter-laminar shear strength (ILSS) among all the carbon fiber reinforced epoxy (CE) composites at all in-situ temperatures. CNT modified CE composite showed increment of 9% in flexural strength and 17.43% in ILSS when compared to that of unmodified CE composite at room temperature (30°C). Thermomechanical properties were investigated using dynamic mechanical analysis. Fractography was also carried out to study different modes of failure of the composites.     

Interface improvement of carbon fiber/methylphenylsilicone resin composites by fiber surface coating of polyhedral oligomeric silsesquioxanes

To enhance interfacial properties of carbon fibers (CFs)-reinforced methylphenylsilicone resin (MPSR) composites, we introduced an appropriate interface reinforced by trisilanolphenyl-polyhedral oligomeric silsesquioxanes (trisilanolphenyl-POSS) between CFs and MPSR with a liquid phase deposition strategy. Chemical bonds among silanol groups of trisilanolphenyl-POSS, hydroxyl-functionalized CF (CF–OH), and silanol end groups of MPSR in the coating were expected to be formed through condensation reaction during the prepared process. CFs with and without sizing treatment-reinforced MPSR composites were prepared by a compression molding method. X-ray photoelectron spectroscopy revealed that trisilanolphenyl-POSS particles enhanced the contents of fiber surface oxygen-containing groups and silicon-containing functional groups. Scanning electron microscopy and atomic force microscopy images showed that trisilanolphenyl-POSS nanoparticles have been introduced onto the fiber surface obviously and the surface roughness increased sharply. Dynamic contact angle analysis indicated that trisilanolphenyl-POSS-modified sizing agent could improve the fiber wettability and surface energy significantly. Short-beam bending test and impact toughness test results showed that the interlaminar shear strength and impact resistance of the sized CFs composites were enhanced greatly with increasing amplitudes of more than 35 and 27% in comparison with those of untreated CF composites, respectively. Cryo-fractured surface topographies of composites confirmed that interfacial adhesion between CFs and MPSR has been improved after sizing treatment. Meanwhile, the sizing treatment does not decrease single fiber tensile strength.     

Microstructure and properties of carbon fiber sized with pickering emulsion based on graphene oxide sheets and its composite with epoxy resin

The Graphene oxide (GO) sheets were used for preparing the epoxy resin Pickering emulsion. The particle size and the zeta potential of the Pickering emulsion were measured to evaluate its stability. The stable emulsion could be served as the film former of sizing agent for carbon fiber (CF). The effect of the Pickering emulsion stabilized by GO sheets on the properties of CF and the interfacial adhesion property of CF reinforced composite were investigated. Scanning electron microscopy (SEM) images showed that there existed a layer of sizing agent film with GO sheets evenly on the CF surface. Abrasion resistance and stiffness values of CF were tested and the results indicated that the sized CF conformed to the requirement of CF handleability. The interlaminar shear strength (ILSS) test indicated that the interfacial adhesion of the composite could be greatly improved. The fracture surfaces of CF composites were examined by SEM after ILSS tests. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42285.     

碳纤维/聚苯并(噁)嗪复合材料的界面与力学性能的关系研究

本文采用含不同上胶剂的碳纤维与苯并(噁)嗪树脂复合,制备碳纤维/聚苯并(噁)嗪单向复合材料,研究了碳纤维表面上胶剂对于复合材料的层间剪切强度(ILSS)、弯曲性能、断口形貌及动态机械性能的影响.结果表明,含有环氧树脂上胶剂的碳纤维/苯并(噁)嗪树脂基复合材料(EPCF/PBZ)的ILSS和弯曲性能优于含非环氧类树脂上胶剂的碳纤维/苯并(噁)嗪树脂基复合材料(VECF/PBZ)和不含上胶剂的碳纤维/苯并(噁)嗪树脂基复合材料(USCF/PBZ).环氧树脂上胶剂改善了纤维与苯并(噁)嗪树脂的粘结性能,使复合材料的内耗峰峰高降低,能量损耗减小.电镜照片同样验证了这一结果.     

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。     

EP/BMI树脂基碳纤维复合材料的制备与性能表征

以环氧树脂(EP)、双马来酰亚胺(BMI)、4,4’-二氨基二苯砜(DDS)和短切碳纤维(SCF)等为主要原料制备了EP/BMI/DDS/SCF复合材料,并研究了SCF添加量对复合材料力学性能和热性能的影响。结果表明,当SCF添加量为0.25 %(质量分数,下同)时,EP/BMI/DDS/SCF复合材料的力学性能提高最大,其拉伸强度、弯曲强度、弯曲模量和缺口冲击强度比未添加SCF时的EP/BMI/DDS复合材料分别提高了48.52 %、32.15 %、25.77 %以及150.91 %;此外,SCF的加入有助于提高复合材料的热性能。     

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.     

Effects of silanization of C/C composites and grafting of h-BN fillers on the microstructure and interfacial properties of CVI-based C/C-BN composites

A low-density carbon/carbon (C/C) composite/silane coupling agent/hexagonal boron nitride (h-BN) hybrid reinforcement was prepared by grafting polyethyleneimine (PEI)-encapsulated modified h-BN fillers onto a carbon fiber surface using 3-aminopropyltriethoxysilane (APS) as the connection to improve the distribution uniformity of h-BN fillers in quasi-three-dimensional reinforcements and the interfacial properties between the fibers/pyrocarbon (PyC) in the C/C-BN composites obtained after densification by chemical vapor infiltration (CVI). The microstructure and chemical components of the hybrid reinforcement were investigated. The transmission electron microscopy (TEM) sample was prepared using a focused-ion beam (FIB) for the h-BN/PyC interfacial zone. The interlaminar shear strength (ILSS) and impact toughness were analyzed to inspect the composites’ interfacial properties. The results show that APS and h-BN are uniformly grafted on the fiber surface in the chopped fiber web inside the C/C composite without a density gradient, and agglomeration occurred and significantly increasing the fiber surface roughness. The highly ordered h-BN basal plane may affect the order degree of PyC near the h-BN/PyC interface. The addition of h-BN reduces the PyC texture near it, causing the annular cracks to disappear gradually. The lower PyC texture and the rougher fiber surface strengthen the interfacial bond of the fiber/matrix. Consequently, the ILSS strength of the C/C-BN composites first increases and then decreases as the h-BN filler content increases and is always higher than that of the C/C composite, while the addition of h-BN fillers weakens its impact toughness. When the h-BN content in the C/C-BN composite is 10 vol%, the ILSS of the C/C-BN composites was 15.6% higher than that of the C/C composites. However, when the h-BN content is excessive (15 vol%), the densely grafted h-BN will bridge each other, reducing the subsequent CVI densification efficiency to form a loose interface, causing a decrease in the shear strength.     

Effect of polyurethane sizing agent on interface properties of carbon fiber reinforced polycarbonate composites

This work is aimed at investigating how molecule structure of polyurethanes (PUs) as sizing agents influence the interface properties of carbon fiber (CF) reinforced polycarbonate (PC) composites. Effects of four PUs as sizing agents for CF on the interlaminar shear strength (ILSS) of CF reinforced PC composites are investigated. It is found that the three PUs except PC–PU as sizing agents on oxidized CF (OCF) made the ILSS of their reinforced PC composites increase up to 62.9 MPa by more than 24.8%. The chemical interaction between PU sizing agents and CF are attributed to high reactivity of isocyanate, but carbonate groups on PC–PU may have a chain unzipping reaction due to active groups on the surface of OCF. The chemical interaction between PU sizing agents and PC are attributed to transesterification. As a result, PUs containing isocyanate or polyester groups are ideal sizing agents for CF reinforced PC composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47982.     

Effect of the concentration of the sizing agent on the carbon fibers surface and interface properties of its composites

The effect of the concentration of the sizing agent on performances of carbon fiber and carbon fiber composites has been investigated. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were applied to characterize carbon fiber surface topographies. At the same time, the single fiber strengths and Weibull distribution were also studied. The interlaminar shear strength and hygrothermal ageing test have been used to study the effect of fiber coatings on the interface of the composites. The analysis of the results shows that the sizing level is essential for improving the surface of carbon fibers and its composite performance. Different concentrations of the sizing agent have different contributions to the wetting performance of carbon fibers. Among the three concentrations of sizing agent studied (1 wt %, 1.5 wt %, and 2 wt %), the optimal sizing level is 1.5 wt %. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci 125:425–432, 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.