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    Investigation of the nanostructure and mechanical properties of polypropylene/polyamide 6/layered silicate ternary nanocomposites

    , Article Materials and Design ; Volume 31, Issue 4 , April , 2010 , Pages 1776-1784 ; 02641275 (ISSN) Motamedi, P ; Bagheri, R ; Sharif University of Technology
    This work aims to investigate the structure-property relationship in ternary nanocomposites consisting of polypropylene as the matrix, nanoclay as the reinforcement and polyamide 6 as the intermediate phase. In this regard, composites of polypropylene/organoclay, polyamide/organoclay, blends of polypropylene/polyamide, and ternary nanocomposites of polypropylene/polyamide/layered silicate with and without compatibilizer were produced via melt compounding. Nanostructure was investigated by wide-angle X-ray diffraction and transmission electron microscopy. Scanning electron microscopy was employed to study the microstructure. Modulus of elasticity and yield strength were measured by uniaxial... 

    Nonlinear thermoelastic stress analysis of the rotating FGM disk with variable thickness and temperature-dependent material properties using finite element method

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 14 , 2010 , Pages 359-364 ; 9780791843871 (ISBN) Azadi, M ; Damircheli, M ; Sharif University of Technology
    In this paper, nonlinear radial and hoop thermoelastic stress analysis of rotating disk made of functionally graded material (FGM) with variable thickness is carried out by using the finite element method. In this method, one-dimensional second order elements with three nodes have been used. The geometrical and boundary conditions are in the shape of nonexistence of the pressure (zero radial stress) in both external and internal layers and zero displacement at the internal layer of rotating disk. Furthermore, it's assumed that heat distribution is as second order curve while material properties such as elasticity modulus, Poisson's ratio and thermal expansion coefficient vary by using a... 

    Suction-induced hardening effects on the shear modulus of unsaturated silt

    , Article International Journal of Geomechanics ; Volume 16, Issue 6 , 2016 ; 15323641 (ISSN) Khosravi, A ; Salam, S ; McCartney, J. S ; Dadashi, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE) 
    The small-strain shear modulus Gmax is a key material parameter in modeling the behavior of soils subjected to dynamic loading. Recent experimental results indicate that seasonal weather interaction with near-surface soils causes Gmax to change by up to an order of magnitude in some climates, with a hysteretic response upon drying and wetting. The increase in Gmax during drying and the stiffer response during subsequent wetting have been postulated to be due to plastic hardening during drying. To further understand this behavior, a series of isotropic compression tests were performed on compacted silt specimens at different values of matric suction to evaluate changes in the preconsolidation... 

    Layerwise theory in modeling of magnetorheological laminated beams and identification of magnetorheological fluid

    , Article Mechanics Research Communications ; Volume 77 , 2016 , Pages 50-59 ; 00936413 (ISSN) Naji, J ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Elsevier Ltd 
    In recent years, structures integrated with magnetorheological (MR) fluid have been considered for their tunable dynamic characteristics. Shear modulus of MR layer in composite structure is dramatically lower than the elastic layers, leading to high shear deformation inside the MR layer, thus classical theories are not accurate enough to predict the dynamic behavior of such structures. In present study a layerwise displacement theory has been utilized to predict a more accurate deformation for MR-composite beam and equation of motions derived using finite element model (FEM). ASTM E756-98 was employed to evaluate the complex shear modulus of MR fluid. By experimental test a practical... 

    Molecular dynamics simulation for interlayer interactions of graphene nanoribbons with multiple layers

    , Article Superlattices and Microstructures ; Volume 98 , 2016 , Pages 228-234 ; 07496036 (ISSN) Nazemnezhad, R ; Zare, M ; Hosseini Hashemi, Sh ; Shokrollahi, H ; Sharif University of Technology
    Academic Press 
    A new study is conducted with the aid of molecular dynamics (MD) simulation to investigate the effect of shear modulus value of the interlayer van der Waals (vdWs) interactions on free vibration of cantilever multi-layer graphene nanoribbons (MLGNRs). The corresponding calibrated nonlocal parameters of the nonlocal model are obtained accordingly. The vdWs interactions are treated as the cores between every two adjacent graphene layers and their equivalent shear modulus is calculated using MD simulation. The obtained resonant frequencies via the nonlocal sandwich model are compared to the MD simulation results to calibrate the nonlocal parameter. Results reveal a strong conclusion that the... 

    Molecular dynamics simulation of nanoindentation of nanocrystalline Al/Ni multilayers

    , Article Computational Materials Science ; Volume 112 , 2016 , Pages 175-184 ; 09270256 (ISSN) Chamani, M ; Farrahi, G. H ; Movahhedy, M. R ; Sharif University of Technology
    Molecular dynamics simulations are employed to investigate material properties of nanocrystalline aluminum and nanocrystalline Al/Ni multilayers at low temperature. For this purpose, both single crystal and nanocrystalline multilayers with different grain sizes and grain morphology are used as the substrate. The results of the simulations show that hardness and elastic modulus decrease with refinement of grain size in nanocrystalline aluminum and refinement of grain size and layer thickness in nanocrystalline Al/Ni multilayers, regardless of grain morphology. Furthermore, the angle between two adjacent grains, which is directly connected to the grain boundary thickness, has a great influence... 

    A novel method for production of foamy core@compact shell Ti6Al4V bone-like composite

    , Article Journal of Alloys and Compounds ; Volume 656 , 2016 , Pages 416-422 ; 09258388 (ISSN) Ahmadi, S ; Sadrnezhad, S. K ; Sharif University of Technology
    Elsevier Ltd 
    This paper presents a novel method for fabrication of bone-like Ti6Al4V foamy core@compact shell composite for utilization as substitutive implant for cortical bone having porous core. Seven prototypes with core-diameters of 0, 6, 8, 10, 12, 14 and 16 mm surrounded by dense shells of respective thicknesses 8, 5, 4, 3, 2, 1 and 0 were produced by an innovative two-stage packing/compaction sintering method. Density, porosity, Young's modulus and compression strength of the prototypes depended on the core diameter. Mechanical strength and Young's modulus of 10@16 (10 mm core, 16 mm diameter prototypes) resembled that of the human ulna bone. Creation of foam at the center was achieved by... 

    Numerical study of material properties, residual stress and crack development in sintered silver nano-layers on silicon substrate

    , Article Scientia Iranica ; Volume 23, Issue 3 , 2016 , Pages 1037-1047 ; 10263098 (ISSN) Keikhaie, M ; Movahhedy, M. R ; Akbari, J ; Alemohammad, H ; Sharif University of Technology
    Sharif University of Technology  2016
    In order to improve the performance of thin film devices, it is necessary to characterize their mechanical, as well as electrical, properties. In this work, a model is developed for analysis of the mechanical and electrical properties and the prediction of residual stresses in thin films of silver nanoparticles deposited on silicon substrates. The model is based on inter-particle diffusion modeling and finite element analysis. Through simulation of the sintering process, it is shown how the geometry, density, and electrical resistance of the thin film layers are changed by sintering conditions. The model is also used to approximate the values of Young's modulus and the generated residual... 

    Fabrication mechanism of nanostructured HA/TNTs biomedical coatings: an improvement in nanomechanical and in vitro biological responses

    , Article Journal of Materials Science: Materials in Medicine ; Volume 27, Issue 10 , 2016 ; 09574530 (ISSN) Ahmadi, S ; Riahi, Z ; Eslami, A ; Sadrnezhaad, S. K ; Sharif University of Technology
    Springer New York LLC  2016
    In this paper, a mechanism for fabrication of nanostructured hydroxyapatite coating on TiO2 nanotubes is presented. Also, the physical, biological, and nanomechanical properties of the anodized Ti6Al4V alloy consisting TiO2 nanotubes, electrodeposited hydroxyapatite, and the hydroxyapatite/TiO2 nanotubes double layer coating on Ti6Al4V alloy implants are compared. Mean cell viability of the samples being 84.63 % for uncoated plate, 91.53 % for electrodeposited hydroxyapatite, and 94.98 % for hydroxyapatite/TiO2 nanotubes coated sample were in the acceptable range. Merely anodized prototype had the highest biocompatibility of 110 % with respect to the control sample. Bonding strength of... 

    Mechanical properties of graphene oxide: A molecular dynamics study

    , Article Fullerenes Nanotubes and Carbon Nanostructures ; Volume 24, Issue 9 , 2016 , Pages 594-603 ; 1536383X (ISSN) Khoei, A. R ; Sarkari Khorrami, M ; Sharif University of Technology
    Taylor and Francis Inc 
    In this paper, the mechanical properties of graphene oxide are obtained using the molecular dynamics analysis, including the ultimate stress, Young modulus, shear modulus and elastic constants, and the results are compared with those of pristine graphene. It is observed that the increase of oxide agents (–O) and (–OH) leads to the increase of C–C bond length at each hexagonal lattice and as a result, alter the mechanical properties of the graphene sheet. It is shown that the elasticity modulus and ultimate tensile strength of graphene oxides (–O) and (–OH) decrease significantly causing the failure behavior of graphene sheet changes from the brittle to ductile. The results of shear loading... 

    Design, fabrication and characterization of oxidized alginate-gelatin hydrogels for muscle tissue engineering applications

    , Article Journal of Biomaterials Applications ; Volume 31, Issue 1 , 2016 , Pages 152-161 ; 08853282 (ISSN) Baniasadi, H ; Mashayekhan, S ; Fadaoddini, S ; Haghirsharifzamini, Y ; Sharif University of Technology
    SAGE Publications Ltd  2016
    In this study, we reported the preparation of self cross-linked oxidized alginate-gelatin hydrogels for muscle tissue engineering. The effect of oxidation degree (OD) and oxidized alginate/gelatin (OA/GEL) weight ratio were examined and the results showed that in the constant OA/GEL weight ratio, both cross-linking density and Young's modulus enhanced by increasing OD due to increment of aldehyde groups. Furthermore, the degradation rate was increased with increasing OD probably due to decrement in alginate molecular weight during oxidation reaction facilitated degradation of alginate chains. MTT cytotoxicity assays performed on Wharton's Jelly-derived umbilical cord mesenchymal stem cells... 

    Finite element analysis of a CFRP reinforced retaining wall

    , Article Geomechanics and Engineering ; Volume 10, Issue 6 , 2016 , Pages 757-774 ; 2005307X (ISSN) Ouria, A ; Toufigh, V ; Desai, C ; Toufigh, V ; Saadatmanesh, H ; Sharif University of Technology
    Techno Press 
    Soils are usually weak in tension therefore different materials such as geosynthetics are used to address this inadequacy. Worldwide annual consumption of geosynthetics is close to 1000 million m2, and the value of these materials is probably close to US$1500 million. Since the total cost of the construction is at least four or five times the cost of the geosynthetic itself, the impact of these materials on civil engineering construction is very large indeed. Nevertheless, there are several significant problems associated with geosynthetics, such as creep, low modulus of elasticity, and susceptibility to aggressive environment. Carbon fiber reinforced polymer (CFRP) was introduced over two... 

    Thermo-mechanical analysis of Roller Compacted Concrete (RCC) dams (Jahgin Dam)

    , Article Proceedings of the Symposium on the Application of Geophyics to Engineering and Environmental Problems, SAGEEP, 29 March 2009 through 2 April 2009, Fort Worth, TX ; Volume 1 , 2009 , Pages 417-427 ; 15548015 (ISSN) ; 9781615670512 (ISBN) Shamsai, A ; Ghaemian, M ; Azimfar, S. M ; Sharif University of Technology
    In this paper a procedure for two-dimensional unsteady thermo-mechanical analysis of layered structures is presented, allowing the determination of the temperature and stress field at each step the construction period. The finite element method is employed in the methodology. Numerical simulation are focused on concrete structures, particularly roller compacted concrete (RCC) dams. A time varying elasticity modulus is introduced in the model. One case study is presented and analysis under different design approaches. Thermal effects must be considered in the process of designing of certain types of concrete structures in order to prevent the damage during either the construction phase (early... 

    Preparation and characteristics of epoxy/clay/B4C nanocomposite at high concentration of boron carbide for neutron shielding application

    , Article Radiation Physics and Chemistry ; Volume 141 , 2017 , Pages 223-228 ; 0969806X (ISSN) Kiani, M. A ; Ahmadi, S. J ; Outokesh, M ; Adeli, R ; Mohammadi, A ; Sharif University of Technology
    In this research, the characteristics of the prepared samples in epoxy matrix by means of X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), as well as scanning electron microscope (SEM) are evaluated. Meanwhile, the obtained mechanical properties of the specimen are investigated. Thermogravimetric analysis (TGA) is also employed to evaluate the thermal degradation of manufactured nanocomposites. The thermal neutron absorption properties of nanocomposites containing 3 wt% of montmorillonite nanoclay (closite30B) have been studied experimentally, using an Am-Be point source. Mechanical tests reveal that the higher B4C concentrations, the more tensile strengths, but lower... 

    Physical, morphological, and biological studies on PLA/nHA composite nanofibrous webs containing equisetum arvense herbal extract for bone tissue engineering

    , Article Journal of Applied Polymer Science ; Volume 134, Issue 39 , 2017 ; 00218995 (ISSN) Khakestani, M ; Jafari, S. H ; Zahedi, P ; Bagheri, R ; Hajiaghaee, R ; Sharif University of Technology
    A series of herbal extract incorporated into poly(lactic acid) (PLA) composite nanofibrous scaffolds were successfully prepared by using electrospinning technique. Equisetum arvense extract (EE) and nanohydroxyapatite (nHA) in different quantities were loaded into PLA solution to fabricate composite nanofibrous webs under various electrospinning conditions. Uniform nanofibers were obtained with an average diameter of 157 ± 47 nm in the case of those containing the herbal extract. Characterization of the webs was carried out by means of Fourier transform infrared (FTIR) spectroscopy, field emission-scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), and... 

    Development of an accurate finite element model for N-layer MR-laminated beams using a layerwise theory

    , Article Mechanics of Advanced Materials and Structures ; 2017 , Pages 1-8 ; 15376494 (ISSN) Momeni, S ; Zabihollah, A ; Behzad, M ; Sharif University of Technology
    Taylor and Francis Inc  2017
    Laminated composite beams incorporated with magneto-rheological fluid are being used in variety of critical applications. An N-layer magneto-rheological-laminated beam based on layerwise theory has been developed to study the dynamic characteristics. For simulation purpose, an MR-laminated beam with five layers is considered in which two layers filled with magneto-rheological and three layers are made of composite materials. The results of simulations are compared with existing layerwise, first-order shear-deformation theory and experimental tests where it shows the accuracy and functionality of the present model. The complex shear modulus of magneto-rheological fluid has been determined... 

    Elastic moduli tensors, ideal strength, and morphology of stanene based on an enhanced continuum model and first principles

    , Article Mechanics of Materials ; Volume 110 , 2017 , Pages 1-15 ; 01676636 (ISSN) Shodja, H. M ; Ojaghnezhad, F ; Etehadieh, A ; Tabatabaei, M ; Sharif University of Technology
    Elsevier B.V  2017
    The present work aims to provide an accurate description of the tensile behavior of the planar as well as low-buckled stanene and to capture their ideal strength in armchair (AC)- and zigzag (ZZ)-directions. For an accurate description of anisotropic response of such hyperelastic materials as stanene, consideration of a highly nonlinear constitutive model in which up to the fourth power of strains is incorporated is inevitable. By utilizing first principles calculations based on density functional theory (DFT), the second, third, fourth, and fifth order elastic moduli tensors corresponding to both planar and low-buckled states are obtained. Moreover, the morphology of the free-standing... 

    Effective shear modulus of solids reinforced by randomly oriented-/aligned-elliptic nanofibers in couple stress elasticity

    , Article Composites Part B: Engineering ; Volume 117 , 2017 , Pages 150-164 ; 13598368 (ISSN) Shodja, H. M ; Alemi, B ; Sharif University of Technology
    Nowadays, by adding a small amount (about 0.5–5% by weight) of a desired nanomaterial to a matrix having certain properties one may design a multifunctional nanocomposites with a remarkably improved macroscopic properties of interest. The capability of conventional continuum theories in treating the problems of embedded ultra-small inhomogeneity with any of its dimensions comparable to the characteristic lengths of the involved constituent phases is questioned, mainly, on the grounds of the accuracy and the size effect. The micromechanical framework based on the Eshelby's ellipsoidal inclusion theory [1] which has been widely used to estimate the overall behavior of composites falls under... 

    Effect of specimen preparation techniques on dynamic properties of unsaturated fine-grained soil at high suctions

    , Article Canadian Geotechnical Journal ; Volume 54, Issue 9 , 2017 , Pages 1310-1319 ; 00083674 (ISSN) Ng, C. W. W ; Baghbanrezvan, S ; Sadeghi, H ; Zhou, C ; Jafarzadeh, F ; Sharif University of Technology
    Canadian Science Publishing  2017
    The seismic response of soil depends on proper evaluation and use of soil dynamic properties, including shear modulus and damping ratio at various strain levels. Despite extensive studies on the shear modulus and damping ratio of saturated soils, research on the dynamic properties of unsaturated fine-grained soils — especially at high suction — is limited. This study aims to investigate the dynamic properties of loess at a variety of initial states resulting from different specimen preparation techniques (reconstituted, recompacted, and intact) and their evolutions due to suction-induced desiccation. Results of resonant column tests show that at initial states, the specimen preparation... 

    Modeling of stiffening and strengthening in nano-layered silicate/epoxy

    , Article International Journal of Engineering, Transactions A: Basics ; Volume 30, Issue 1 , 2017 , Pages 93-100 ; 17281431 (ISSN) Marouf, B. T ; Pearson, R. A ; Bagheri, R ; Sharif University of Technology
    The aim of this paper is to investigate adhesion property between nano-layered filler and the polymer matrix using a combination of experimental and micromechanical models as well as the changes in yield strength and stiffness of a layered silicate-filled epoxy nanocomposite. The results indicate that addition of intercalated layered silicate particles increased Young's modulus and yield strength of the epoxy resin, although the increases in stiffness and yield strength are modest, 30% and 4%, respectively. In addition, experimental results were compared with predictive stiffening and strengthening models. The rule of mixtures provides an upper bound for the modulus in these materials, while...