Yuwei Wang

Interfacial properties and impact toughness of dendritic hexamethylenetetramine functionalized carbon fiber with varying chain lengths

In order to understand the effects of chain length on the interfacial adhesion of PAN-based carbon fiber (CF)/epoxy composites, dendritic hexamethylenetetramine (HMTA) was functionalized on carbon fibers through quaternary ammonium salt reaction using alkyl dihalide of varying chain length [Cl(CH2)nCl, n = 2, 6 and 12]. Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photoelectron spectroscopy (XPS) confirmed the successful grafting of dendritic HMTA and alkyl dihalide. AFM images showed that dendritic HMTA modified CF surfaces enhanced roughness, and this effect was more pronounced with increasing alkyl dihalide chain length. The results of dynamic contact angle (DCA) and interfacial shear strength (IFSS) demonstrated that the surface energy and interfacial adhesion increased and then decreased with the chain length of alkyl dihalide. The tensile strength and impact roughness of the composites enhanced as the alkyl dihalide chain length grew. Moreover, the reinforcing and toughening mechanisms were also discussed.

Interfacially reinforced carbon fiber/epoxy composites by grafting melamine onto carbon fibers in supercritical methanol

Melamine used as a coupling agent was functionalized onto a carbon fiber (CF) surface in supercritical methanol to improve the interfacial properties of CF reinforced epoxy composites. Fourier transform infrared spectroscopy (FTIR), Raman spectra and X-ray photo electron spectroscopy (XPS) confirmed the successful grafting of melamine molecules onto the fiber surface. Scanning electron microscopy (SEM) images showed that melamine was grafted onto the CF surface uniformly and the surface roughness was enhanced obviously. Dynamic contact angle analysis (DCA) revealed the significant improvement in the surface energy and wettability. Compared with the untreated CF composites, the interfacial shear strength (IFSS) and inter-laminar shear strength (ILSS) of composites after melamine modification increased by 41.3% and 36.4%, respectively. The impact properties were also improved significantly. In addition, the reinforcing and toughening mechanisms were also discussed. Meanwhile, supercritical treatment did not decrease the single filament tensile strength obviously.

Interfacial properties and thermo-oxidative stability of carbon fiber reinforced methylphenylsilicone resin composites modified with polyhedral oligomeric silsesquioxanes in the interphase

The grafting of trisilanolphenyl-polyhedral oligomeric silsesquioxanes (trisilanolphenyl-POSS) onto carbon fibers (CFs) was achieved using toluene-2,4-diisocyanate (TDI) as the bridging agent. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the successful modification of trisilanolphenyl-POSS. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) images showed that trisilanolphenyl-POSS nanoparticles were grafted uniformly onto the surface of CFs and the surface roughness increased significantly. The results of dynamic contact angle (DCA) measurements demonstrated an improvement in the surface energy and wettability that related to the increased polarity of the obtained hybrid fibers (CF-g-POSS). The effects of trisilanolphenyl-POSS grafting on the interfacial, impact, and heat-resistant properties of methylphenylsilicone resin (MPSR) composites were also studied. The interlaminar shear strength (ILSS) and impact resistance of methylphenylsilicone resin (MPSR) composites after POSS modification were improved significantly with increasing amplitudes of 41.91% and 28.65%, respectively. Moreover, the interfacial reinforcing and toughening mechanisms of composites have also been discussed. In addition, the thermal oxygen aging experiments indicated a remarkable improvement in the heat oxidation resistance by the introduction of trisilanolphenyl-POSS in the interphase. Meanwhile, the grafting processes do not decrease fiber tensile strength (TS).

Controlled synthesis of microarc oxidation coating on Ti6Al4V alloy and its antifriction properties

Abstract Ceramic coatings were fabricated on a Ti6Al4V alloy surface by microarc oxidation (MAO) in Na2 SiO3 – (NaPO3)6 aqueous solutions with and without NaAlO2 additive using an AC power supply. The effect of NaAlO2 on microstructure, composition, and homogeneity of ceramic coatings were characterised using SEM, XRD, and EPMA. The antifriction property of the coatings with optimised microstructure sliding against SAE 52 100 steel ball was investigated on a pin-on-disc friction and wear tester. The results show that the addition of NaAlO2 into Na2 SiO3 – (NaPO3)6 solution assists the formation of more dense, uniform, and thicker coatings and increases rutile TiO2 content in the coatings. The optimised coating sliding against the steel has a friction coefficient as low as 0.2 – 0.3 at an applied load of 0.5 N and sliding cycle below 2500, which is much smaller than that of uncoated Ti6Al4V against the same counterpart. The transferring of material from the softer steel ball onto the coating surface is the main wear event, while the microarc oxidation coating is characterised by slight abrasive wear and adhesive wear.

Preparation and properties of carbon nanotube/carbon fiber hybrid reinforcement by a two-step aryl diazonium reaction

Raw carbon nanotube (CNT)/carbon fiber (CF) hybrids were achieved through a two-step aryl diazonium reaction in mild, eco-friendly conditions. Raman spectra, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) confirmed the grafting of CNT onto the CF surface. The surface topography and surface free energy of the modified CFs were examined by scanning electron microscopy (SEM), transmission electron microscope (TEM) and dynamic contact angle (DCA) tests, respectively. The resulting CNT/CF hybrid formed a strong chemical bond between the fiber and matrix and enhanced the surface wettability of the modified CFs. The interfacial shear strength (IFSS) of the CNT/CF hybrid reinforced composites increased by 104% compared with that of the untreated CFs. Moreover, the mechanical properties of the CNT/CF hybrid showed a slight improvement after modification.

Controlled growth of silver nanoparticles on carbon fibers for reinforcement of both tensile and interfacial strength

Metal nanoparticles are commonly used for surface modification in fiber reinforced polymer composites because of their large specific surface area and electronic, magnetic and other related properties. In this study, morphology-controllable silver nanoparticles (Ag NPs) were deposited on a carbon fiber surface via a facile and green electro-chemical deposition method in the presence of poly(vinylpyrrolidone) (PVP). It was found that the presence of PVP and its molar ratio (in terms of repeating unit) relative to silver nitrate both played important roles in determining the geometric shape and size of the Ag NPs. Interestingly, electro-chemical deposition of Ag NPs improved both the tensile strength of the carbon single fiber and the interfacial property of the carbon fiber/epoxy composite by as much as 57.2% and 27.2%, respectively. Moreover, the Ag NPs-loaded carbon fibers exhibited superior electrical conductivity, which was a 2-fold enhancement as compared with that of the virgin carbon fibers. It meant that the Ag NPs-loaded carbon fibers could be used as ideal reinforcement materials for advanced aerospace systems.

Improvements in interfacial and heat-resistant properties of carbon fiber/methylphenylsilicone resins composites by incorporating silica-coated multi-walled carbon nanotubes

Abstract The multi-scale reinforcement and interfacial strengthening on carbon fiber (CF)-reinforced methylphenylsilicone resin (MPSR) composites by adding silica-coated multi-walled carbon nanotubes (SiO2-CNTs) were investigated. SiO2-CNT has been successfully prepared via the hydrolysis of tetraethoxysilane in the presence of acid-oxidized multi-walled carbon nanotubes. Transmission electron microscopy, X-ray diffraction, and Fourier Transform infrared spectroscopy were carried out to examine the functional groups and structures of CNTs. Then, SiO2-CNT was incorporated into MPSR matrix to prepare CF/MPSR-based composites by the compression molding method. The effects of the introduced SiO2-CNT on the interfacial, impact, and heat-resistant properties of CF/MPSR composites were evaluated by short-beam bend method, impact test, and thermal oxygen aging experiments, respectively. Experimental results revealed that the CF/MPSR composites reinforced with 0.5 wt% SiO2-CNT showed a significant increase 34.53% in the interlaminar shear strength (ILSS) and 20.10% in impact properties. Moreover, the heat-resistant properties of composites were enhanced significantly by adding SiO2-CNT hybrid nanoparticles. These enhancements are mainly attributed to the improved matrix performance resulted from the molecular-level dispersion of SiO2-CNT in MPSR matrix and the strong interfacial adhesion between SiO2-CNT and matrix resin, which are beneficial to improve the mechanical stress transfer from MPSR matrix to CFs reinforcement and alleviate stress concentrations.

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.