The current study focuses on the development of silanized graphene oxide reinforced basalt fiber/epoxy composites for enhanced tribological and viscoelastic properties. The modified-graphene oxide nanoplatelets were characterized using energy-dispersive X-ray spectroscopy, and Raman analyses. Pin-on-disk wear test and dynamic mechanical thermal analysis were conducted to determine the tribological and viscoelastic properties of the fabricated specimens with different silanized-graphene oxide loadings in the matrix (0–0.5 wt.% at a step of 0.1). The multiscale specimens were fabricated using the hand lay-up technique. The best silanized-graphene oxide loading for effectively enhancing the tribological properties was found to be 0.4 wt.%, whose wear rate and friction coefficient were 62% and 44%, respectively lower than those of the neat basalt/epoxy composite. The examination of the worn surfaces showed the enhanced basalt fiber/epoxy bonding in graphene oxide-reinforced specimen. From the results of dynamic mechanical thermal analysis, the specimen filled with 0.4 wt.% silanized-graphene oxide demonstrated the highest increase of 130% and 13.6℃ in the storage modulus and glass transition temperature as compared to the neat composite. This study indicated that the addition of silanized-graphene oxide considerably enhanced the tribological and viscoelastic properties of the fibrous composites.
The most important impacts of climate change relate to temperature and precipitation. Precipitation is particularly important, because changes in precipitation patterns may lead to floods or droughts in different areas. Also, precipitation is a major factor in agriculture and in recent years interest has increased in learning about precipitation variability for periods of months to annual and seasonal trends and change points had been analyzed for 22 rainfall stations in Fars province during 1972 to 2011. Mann-Kendall non-parametric test and Sen’s method had been used to determine positive or negative trends; also Pettitt test, Standard normal homogeneity test, Buishand range test, Von Neumann ratio, for detection of change points in the time series had been implemented. The TFPW approach had been used in order to decline the effects of autocorrelation and serial correlation on Mann-Kendall test. The results of Mann-Kendall test and Sen’s Method showed decreasing trend for all rainfall stations except for the Monje station. But, no significant trends were observed in all stations. Also, the results indicated that the precipitation has not occurred nonhomogeneity; whereas all test indicated there is no change point on precipitation time series. No change and abrupt shift were visible in the precipitation time series except in winter for Ali Abad Khafr; and Ali Abad Khafr; Tangab and Ramjerd based on pettitt test and Standard normal homogeneity test, respectively.
The aim of this work was to study the influence of nano-zirconium oxide, graphene oxide, and nano-zirconium oxide + graphene oxide hybrid system on the high-velocity impact behavior and interlaminar shear strength of basalt fiber/epoxy composite. Initially, the nano-zirconium oxide and graphene oxide were functionalized by using a silane-coupling agent namely 3-aminopropyltrimethoxysilane. In order to confirm the surface functionalization of nano-zirconium oxide and graphene oxide, Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy were carried out on both untreated and silanized fillers. Then, 15 types of specimens containing various amounts of nano-zirconium oxide (1, 2, and 3 wt.%), graphene oxide (0.1, 0.3, and 0.5 wt.%), or nano-zirconium oxide + graphene oxide hybrid in the matrix were prepared. The comparative results of the experiments showed that the specimen with 2 wt.% nano-zirconium oxide + 0.1 wt.% graphene oxide had the highest values of energy absorption, impact limit velocity, and interlaminar shear strength. The energy absorption and limit velocity of this specimen enhanced by 67 and 30%, respectively, as compared to the neat basalt fiber/epoxy composite, while its interlaminar shear strength increased by 77%. The fracture surfaces of the specimens demonstrated that the introduction of nanofillers in the matrix improved the adhesion between the basalt fibers and polymeric matrix. The findings of this work clearly showed that the simultaneous addition of graphene oxide and nano-zirconium oxide is a promising method for improving the high-velocity impact properties and interlaminar shear strength of fibrous composites.
Multiscale composites have been investigated by the addition of silanized carbonate calcium (CaCO3) as a secondary reinforcement into the matrix of carbon fiber/epoxy composites. The chemical modification of the CaCO3 nanoparticles was confirmed by Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). Mechanical properties of the specimens were investigated by means of tensile, flexural, and compressive measurements to study the effect of treated CaCO3 loading (0.5, 1, 3 and 5 wt.%) on their mechanical behavior. Experimental results showed that the tensile, flexural and compressive strengths of the specimen filled with 3 wt.% treated CaCO3 composite enhanced by 14%, 36%, and 30% respectively, compared with those of neat one. The highest improvements in the mechanical moduli were observed in the multiscale composite filled with 5 wt.% treated CaCO3. Also, the fracture surface of the specimens was further analyzed in detail.
Abstract This work focuses on the preparation and characterization of multiscale epoxy‐matrix composites reinforced by basalt fibers and carbon nanofiber (CNF). CNF powders were first functionalized with 3‐aminopropyltrimethoxysilane and characterized by Fourier‐transform infrared spectroscopy, and thermogravimetric analysis; then, the epoxy resin was incorporated with 0.05 wt%, 0.1 wt%, 0.3 wt%, and 0.5 wt% f‐CNF. The influence of functionalized‐CNF (f‐CNF) loading on the interlaminar shear strength (ILSS), tensile, and wear behaviors of the multiscale basalt fiber/epoxy composites was studied. Whereas a relatively small improvement (12%) in tensile strength was achieved, a remarkable enhancement in ILSS (73%) was obtained for the multiscale specimen with an f‐CNF loading of 0.3 wt%. Also, the multiscale specimen filled with 0.5 wt% f‐CNF showed an improvement of 37% in tensile modulus. The wear rate and friction coefficient of the 0.3 wt% f‐CNF loaded composite were decreased by 56% and 38% with respect to the neat specimen, respectively. To establish the microstructure‐property relationship, the worn and fractured surfaces of the specimens were analyzed.
The primary aim of this study was to determine the influence of CuO-decorated graphene oxide nanoplatelets (CuO@GONPs) loading (0.05, 0.1, 0.3, 0.5, and 0.7 wt.%) on the flexural and wear properties of epoxy-matrix nanocomposites. It is worth noting that the Copper (II) chloride (CuCl2) was used as a nano-CuO generator on the surface of the GONPs in the presence of NaOH. Various analyses such as X-ray diffraction (XRD), Atomic-force microscopy (AFM), Raman spectra, and energy dispersive X-ray (EDX) confirmed the successful synthesizing of the CuO@GONPs hybrid. The results of the flexural tests revealed that the highest obtained flexural strength and flexural modulus belonged to the specimens containing 0.3 wt.% and 0.5 wt.% CuO@GONPs, with 51.8% and 21.3% enhancements respectively, as compared to the neat epoxy. The wear test results showed that adding 0.5 wt.% CuO@GONPs into the epoxy matrix was caused to decrease the wear rate and friction coefficient by 87.4% and 29.6%, respectively. Additionally, the CuO@GONPs/epoxy nanocomposite denoted better flexural and wear behaviors than the pristine GONPs/epoxy one. Overall, the controlled introduction of the CuO@GONPs hybrid into the epoxy matrix was found to be an effective strategy for enhancing its flexural and wear properties.
This study is primarily focused on the fabrication of nanosilica-decorated graphene oxide (SiO 2 @GNs) and its role in improving the mechanical behavior of Jute fiber/epoxy laminates. To decorate the GNs surfaces with the silica nanoparticles, tetraethyl-orthosilicate (TEOS) was used, and the successful synthesis of the SiO 2 @GNs nanohybrid was confirmed by X-ray diffraction (XRD), atomic force microscopy (AFM), and energy dispersive X-ray analysis (EDX). Further, the influence of adding 0.1, 0.3, and 0.5 wt.% GNs or SiO 2 @GNs on the interlaminar shear strength (ILSS) and dry-sliding wear behavior of the jute fiber/epoxy composites were explored. The specimens were fabricated using the hand lay-up route. Resultantly, the 3 wt.% SiO 2 @GNs/jute fiber/epoxy sample showed the highest ILSS and wear resistance. The addition of 3 wt.% SiO 2 @GNs improved the ILSS of the jute fiber/epoxy by 62%. Besides, reductions of 50% and 78% in the wear rate and coefficient of friction, respectively, were obtained for the sample enhanced with 3 wt.% SiO 2 @GNs. Interestingly, the mechanical properties of the composites were found to improve significantly through the SiO 2 -decoration of the GNs. Finally, to find the dominant mechanisms, the fractured and worn surfaces of the composites were observed using scanning electron microscopy (SEM).
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