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Abstract The anticorrosive and mechanical properties of carbon nanotubes (CNTs) in epoxy resin (EP) coatings have been improved by the integration of molybdenum disulfide (Mo[S.sub.2]) and 3-aminopropyltrimethoxysilane (APTMS) for surface [...]

In the present work, by considering the aggregation effect of single-walled carbon nanotubes (SWCNT), the nonlinear vibration of functionally graded (FG) nanocomposite sandwich Timoshenko beams resting on Pasternak foundation are presented. The material properties of the FG nanocomposite sandwich beam are estimated using the Eshelby-Mori-Tanaka approach and differential quadrature method (DQM) is used to obtain natural frequency. The nonlinear governing equations and boundary conditions are derived using the Hamilton principle and von Karman geometric nonlinearity. The higher order nonlinear governing equations and boundary conditions are calculated using the Hamilton principle. A direct iterative method is employed to determine the nonlinear frequencies and mode shapes of the beams. It is shown that the mechanical properties and therefore vibration of functionally graded carbon nanotube reinforced (FG-CNTR) sandwich beams are severely affected by CNTs aggregation. A detailed parametric study is carried out to investigate the influences of Winkler foundation modulus, shear elastic foundation modulus, length to span ratio, thicknesses of face sheets on the nonlinear vibration of the structure., INTRODUCTION Over the past few years, there has been an ever-increasing interest in the synthesis, characterization, functionalization, molecular modeling, and design of nanocomposite materials. The outstanding and exceptional mechanical, electrical, [...]

In this work, the [beta]-nucleated isotactic polypropylene (iPP)/ ethylene-octene copolymer (POE) blends demonstrated greatly enhanced impact toughness by adding traces of carbon nanotubes (CNTs) (only 0.05 wt%). When the POE content was 30 wt%, the impact strength of [beta]-nucleated iPP/POE blends with CNTs was as high as 51.7 kJ/[m.sup.2], about 5.6 kJ/[m.sup.2] higher than [beta]-nucleated iPP/POE blends, 15.2 kJ/[m.sup.2] higher than CNTs-filled iPP/POE blends, and almost 19 times of pure iPP sample. This significantly improved impact toughness was considered to be attributed to the shear yielding and multiple-crazing, originating from the presence of abundant [beta]-crystals in the iPP matrix, the enhanced mobility of the molecular chains in the confined amorphous region of iPP lamellae and the homogenous distribution of POE dispersed phase with a small size, indicating the synergistic effect of CNTs, [beta]-nucleating agent and POE on the toughness of iPP., INTRODUCTION As a general plastic, isotactic polypropylene (iPP) is widely used in our daily life from common packaging and textile products to components in cutting-edge automobiles and aircraft, due to [...]

In this study, carbon nanotubes reinforced polyoxymethylene with different filler loadings was joined by using linear vibration welding technique. The tensile properties of vibration welded polyoxymethylene nanocomposites with different carbon nanotube contents were studied as functions of filler loading and weld pressure. The results showed that the addition of carbon nanotubes into polyoxymethylene slightly improved the matrix tensile strength and pronounced decreased the ductility of pure polyoxymethylene. Interestingly, the weld strength of the nanocomposites was also higher than the polymer matrix strength even at high weld pressure of 2 MPa. Possible reasons for this high weld strength are discussed based on the morphological investigations., INTRODUCTION Due to their outstanding mechanical properties with low density and high thermal as well as electrical conductivity, carbon nanotubes are used as functional fillers in polymer-based composites for a [...]

Multi-walled carbon nanotubes (MWCNTs), surfacetreated via chemical functionalization, i.e., oxidation and amidation, were used to reinforce diglycidylether of bisphenol F (DGEBF) epoxy resin. The effects of the functionalization on the dispersion stability, rheological properties, and fracture toughness of DGEBF/MWCNT composites were investigated. The dispersion homogeneity of the MWCNTs in the epoxy matrix improved after functionalization. In addition, isothermal rheology measurements revealed that the DGEBF/dodecyl aminefunctionalized MWCNT (D-MWCNT) composite had a longer gel time and higher activation energy of cross-linking than the DGEBF/acid-treated MWCNT (A-MWCNT) composite. The fracture toughness of the former was also significantly higher than that of the latter; this resulted from the relatively high dispersion stability of the D-MWCNTs in the epoxy matrix, owing to the presence of alkyl groups on the D-MWCNT surface. POLYM. ENG. SCI., 55:2676-2682, 2015. [C] 2015 Society of Plastics Engineers, INTRODUCTION Owing to their extraordinary mechanical, thermal, and electrical properties, carbon nanotubes (CNTs) have been used extensively in polymer composites since their discovery by Iijima in 1991. These outstanding electrical [...]

Polyacrylonitrile (PAN) and PAN/carbon nanotube (PAN/ CNT) fibers were manufactured through dry-jet wet spinning and gel spinning. Fiber coagulation occurred in a solvent-free or solvent/nonsolvent coagulation bath mixture with temperatures ranging from -50 to 25°C. The effect of fiber processing conditions was studied to understand their effect on the as-spun fiber cross-sectional shape, as well as the as-spun fiber morphology. Increased coagulation bath temperature and a higher concentration of solvent in the coagulation bath medium resulted in more circular fibers and smoother fiber surface. as-spun fibers were then drawn to investigate the relationship between as-spun fiber processing conditions and the drawn precursor fiber structure and mechanical properties. PAN precursor fiber tows were then stabilized and carbonized in a continuous process for the manufacture of PAN based carbon fibers. Carbon fibers with tensile strengths as high as 5.8 GPa and tensile modulus as high as 375 GPa were produced. The highest strength PAN based carbon fibers were manufactured from as-spun fibers with an irregular cross-sectional shape produced using a -50 C methanol coagulation bath, and exhibited a 61% increase in carbon fiber tensile strength as compared to the carbon fibers manufactured with a circular cross-section. POLYM. ENG. SCI., 55:2603-2614, 2015., INTRODUCTION Gel spinning has been used for the production of polyethylene [1], poly(vinyl alcohol) [2], and PAN [3] fibers, as well as their nanocomposite counterparts [4-8]. Advantages associated with gel [...]

In a systematic manner, the roles of MWNTs as filler and styrene acrylonitrile copolymer-graft-maleic anhydride (SAN-MA) as compatibilizer, individually and together, on dynamic-mechanical behavior of polycarbonate (PC)-rich/ acrylonitrile butadiene styrene terpolymer (ABS) blend were studied. The investigations were performed using small-scale mixing in a one-step procedure with a fixed MWNTs content of 0.75 wt% and a blend composition of PC/ABS = 70/30 w/w. PC/SAN blends and nanocomposites as simpler model system for PC/ABS were also studied to reveal the role of the rubbery polybutadiene (PB) fraction. It is found that the tendency of MWNTs to localize within the PC component in compatibilized PC/ABS was lower than in compatibilized PC/SAN blends. Dynamic mechanical analysis (DMA) revealed the dual role of SAN-MA as blend compatibilizer and also promoter of MWNTs migration towards PC, where SAN-MA to MWNTs weight ratio varied between 1 and 4. At the compatibilizer/MWNTs weight ratio of 1, MWNTs localized in PC component of the blends whereas increasing the compatibilizer/MWNTs ratio to 4 led to migration of MWNTs toward SAN or ABS component. In DMA studies, loss modulus normalization of the nanocomposites revealed the coexistence of mobilized and immobilized regions within the nanocomposite structure, as a result of MWNTs and compatibilizer loading., INTRODUCTION Fillers play an essential role to adjust the polymers' advantageous characteristics to reach the property balance needed for certain applications. It is expected that high aspect ratio as well [...]

The effect of montmorillonite and shear stress on the orientation of single walled carbon nanotubes and properties of SWCNT/MMT/polypropylene composite was investigated. The effect of functionalization of SWCNT on the orientation was also investigated. Polarized Raman spectroscopy was used to analyze the orientation of the SWCNTs. Orientation of SWCNTs was dependent on the experienced shear stress and functionalization of SWCNTs. The addition of MMT also improved the orientation of functionalized SWCNTs, while its effect was not significant for pristine SWCNTs. The existence of critical shear stress was observed for the orientation of the SWCNTs and the orientation of SWCNTs was found to occur more efficiently above this critical shear stress. Melt viscosity and heat of fusion data also confirmed that the addition of MMT-induced improved orientation and dispersion of SWCNTs, especially for functionalized SWCNTs., INTRODUCTION Carbon nanotubes (CNTs) have garnered attention as fillers due to their superior electrical and mechanical properties. CNTs, however, tend to agglomerate due to strong van der Waals force interactions, [...]

Different micromechanical models which account for the presence of dispersed and agglomerated nanofillers, specifically carbon nanotubes (CNTs) and cellulose nanowhiskers (CWs), in a polymeric matrix and consider the effect of a percolation threshold on the elastic modulus of the composite are derived and compared. We demonstrate that the critical filler volume fraction where a percolating network is forming marks a 'turning point' in the reinforcement efficiency. The suitability of these models is verified by comparing simulated values with experimental data from literature. The results show that the models are able to predict mechanical properties over a wide range of testing conditions. POLYM. ENG. Sd., 53:882-887, 2013. © 2012 Society of Plastics Engineers, INTRODUCTION Nanocomposites are a class of composites in which one of the dimensions of the reinforcement phase is in the range of 1-100 nm. Because of the filler nanometer size [...]

The effects of carbon nanotube (CNT) inclusion on cyclic fatigue behavior and the residual mechanical properties of epoxy composites after different degrees of fatigue have been studied. Tension-tension cyclic fatigue tests were conducted at various load levels (25-50 MPa) to establish the relationship between stress and the number of cycles to failure (S-N curves). The residual strength and modulus were measured after loading at 30 MPa for 5000, 15,000, and 25,000 cycles. The incorporation of a small amount of CNTs increased the fatigue life of epoxy in the high-cycle, low-stress-amplitude regime by 1550%. Micrographs indicate the key mechanisms for enhancement in fatigue life such as CNT crack-bridging and pullout. POLYM. ENG. SCI., 52:1882-1887, 2012. © 2012 Society of Plastics Engineers, INTRODUCTION Because of the outstanding mechanical and physical properties and large specific surface area of carbon nanotubes (CNTs), CNT-based composites are expected to show significantly improved mechanical performance, when compared [...]