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    Interface behavior between carbon-fiber polymer and sand

    , Article Journal of Testing and Evaluation ; Volume 44, Issue 1 , 2016 , Pages 385-390 ; 00903973 (ISSN) Toufigh, V ; Ouria, A ; Desai, C. S ; Javid, N ; Toufigh, V ; Saadatmanesh, H ; Sharif University of Technology
    ASTM International  2016
    Interface shear strength between soil and structural materials is dependent on the confining pressure. To increase the confining pressure, different methods of reinforcement and materials, such as carbon-fiber-reinforced polymer (CFRP) can be used. The shear strength of CFRP-improved soil is dependent on the interface properties of the soil and CFRP. The objective of this study is to investigate the interface properties (friction angle and adhesion) of sand and FRP experimentally using the direct shear test apparatus. To increase the surface roughness to improve the interface properties, a layer of sand was placed on saturated carbon fiber during the curing period [spark plasma sintering... 

    A numerical investigation on the cure cycle of composite brake blocks

    , Article International Polymer Processing ; Volume 21, Issue 4 , 2006 , Pages 421-431 ; 0930777X (ISSN) Shojaei, A ; Sharif University of Technology
    Carl Hanser Verlag  2006
    Composite friction materials used in the braking system of vehicles are composed of different ingredients (typically up to 20 materials). The overall physical properties of these products are determined by the type and percentage of the individual ingredients in the final composition and consequently, may differ from one product to another. This paper studies the cure characteristics of railroad composite brake blocks during compression molding. Numerical simulations using the control volume/finite element method (CV/FEM) are utilized to predict temperature fields and cure conversion during the process. As railroad brake blocks are normally thick-sectioned parts, a three-dimensional modeling... 

    Morphological and mechanical properties of styrene butadiene rubber/nano copper nanocomposites

    , Article Results in Physics ; Volume 7 , 2017 , Pages 338-344 ; 22113797 (ISSN) Hadizadeh Harandi, M ; Alimoradi, F ; Rowshan, G ; Faghihi, M ; Keivani, M ; Abadyan, M ; Sharif University of Technology
    Elsevier B.V  2017
    In this research, rubber based nanocomposites with presence of nanoparticle has been studied. Styrene butadiene rubber (SBR)/nanocopper (NC) composites were prepared using two-roll mill method. Transmission electron microscope (TEM) and scanning electron microscope (SEM) images showed proper dispersion of NC in the SBR matrix without substantial agglomeration of nanoparticles. To evaluate the curing properties of nanocomposite samples, swelling and cure rheometric tests were conducted. Moreover, the rheological studies were carried out over a range of shear rates. The effect of NC particles was examined on the thermal behavior of the SBR using thermal gravimetric analysis (TGA). Furthermore,... 

    The impact of long-term curing period on the mechanical features of lime-geogrid treated soils

    , Article Geomechanics and Geoengineering ; 19 March , 2020 Jahandari, S ; Mojtahedi, S. F ; Zivari, F ; Jafari, M ; Mahmoudi, M. R ; Shokrgozar, A ; Kharazmi, S ; Vosough Hosseini, B ; Rezvani, S ; Jalalifar, H ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    One problem that has always been a challenge for geotechnical engineers is construction on problematic and soft soils. Traditional methods of lime and cement stabilisation can be used to treat soils with these properties. The main drawback of lime addition to the clayey soils is a significant loss in ductility of lime-treated soils. Using ductile materials such as geogrids in lime-treated soils is one of the most effective ways to increase the soil ductility. Therefore, the effect of geogrids and lime on unconfined compressive strength (UCS), failure strain (ɛf), secant modulus (Es), deformability indexes (ID), resilient modulus (Mr), bulk modulus (K), and shear modulus (G) of the treated... 

    Cure kinetic and network structure of NR/SBR composites reinforced by multiwalled carbon nanotube and carbon blacks

    , Article Thermochimica Acta ; Volume 566 , 2013 , Pages 238-248 ; 00406031 (ISSN) Ahmadi, M ; Shojaei, A ; Sharif University of Technology
    Low structure carbon black (CBN330), conductive high structure carbon black (CBXE2B) and carboxylated multiwalled carbon nanotube (MWCNT) were loaded into the blend of natural rubber (NR) and styrene butadiene rubber (SBR) at different contents up to 10 phr. Kraus plots showed that all the reinforcements interact with NR/SBR blend appropriately. However, the CBXE2B whose interfacial area is the highest showed greatest value of Kraus interaction parameter. Flory-Rhener model and effective torque value revealed that all of the reinforcements enhanced the crosslink density, among them CBXE2B showed the highest impact and MWCNT placed in the second rank. It was also shown that the cure kinetic... 

    Three-dimensional process cycle simulation of composite parts manufactured by resin transfer molding

    , Article Composite Structures ; Volume 65, Issue 3-4 , 2004 , Pages 381-390 ; 02638223 (ISSN) Shojaei, A ; Ghaffarian, S. R ; Karimian, S. M. H ; Sharif University of Technology
    A process cycle of resin transfer molding (RTM) consists of two sequential stages, i.e. filling and curing stages. These two stages are interrelated in non-isothermal processes so that the curing stage is dominated by the resin flow as well as temperature and conversion distributions during the filling stage. Therefore, it is necessary to take into account both filling and curing stages to analyze the process cycle accurately. In this paper, a full three-dimensional process cycle simulation of RTM is performed. Full three-dimensional analysis is necessary for thick parts or parts having complex shape. A computer code is developed based on the control volume/finite element method (CV/FEM).... 

    Synthesis and Application of Superabsorbent Nanocomposites for Optimized Performance in Cement-based Materials

    , Ph.D. Dissertation Sharif University of Technology Fakourpour, Mahmoud (Author) ; Pourjavadi, Ali (Supervisor)
    Superabsorbent polymers are mainly used in baby diapers and in agriculture. A less known emerging and potentially important application is the internal curing of cement based materials. About a decade ago, pioneering works demonstrated that using SAP in concrete reduces autogenous shrinkage and cracking, and improves hydration of the cement matrix. However, problems like workability reduction, and deterioration of mechanical strength of the mixture are reported. In this thesis, nanocomposites using nanosilica and acrylic monomers were prepared and used to address the above problems. Nanocomposites exhibit enhanced mechanical strength and reduced sliding friction, compared with conventional... 

    Investigation on the Role of Curing System on the Cure Kinetics and Network Structure of NR/SBR Blend Filled with Nanodiamond

    , M.Sc. Thesis Sharif University of Technology Rabiei, Sima (Author) ; Shojaei, Akbar (Supervisor)
    Vulcanization is one the most crucial process in elastomer manufacturing products. It has been shown that network structure and curing kinetic are strongly dependent on curing system formulation. In addition reinforcing fillers in elastomers can affect them as well. By commencement of nanofillers in rubber domain, effects of nanofiller presence on rubber behavior have been investigated by reaserchers.
    In this Project the effect of different curing system formulations on vulcanization kinetic and network structure of NR/SBR elastomeric matrice filled by nanodiamond is investigated. Different ingredients and nanodiamond were added to matrix by mechanical mixing in two roll mill. The... 

    Effect of carbon-based nanoparticles on the cure characteristics and network structure of styrene-butadiene rubber vulcanizate

    , Article Polymer International ; Volume 61, Issue 4 , 2012 , Pages 664-672 ; 09598103 (ISSN) Saatchi, M. M ; Shojaei, A ; Sharif University of Technology
    The network structure of styrene-butadiene rubber (SBR) in the presence of carbon black (CB) with two different structures and multi-walled carbon nanotubes (MWCNTs) was investigated. Swelling behaviour, tensile properties at various strain rates and cure kinetics were characterized. Experimental data were analysed using the Flory-Rehner model as well as the tube model theory. It is found that the network structure of CB-filled SBR follows a three-phase composite model including rigid particles, semi-rigid bound rubber and matrix rubber. This bound rubber is postulated to be critical for the mechanical and deformational properties, development of crosslinking density in matrix rubber and... 

    Waste ceramic powder-based geopolymer mortars: effect of curing temperature and alkaline solution-to-binder ratio

    , Article Construction and Building Materials ; Volume 227 , 2019 ; 09500618 (ISSN) Shoaei, P ; Musaeei, H. R ; Mirlohi, F ; Narimani zamanabadi, S ; Ameri, F ; Bahrami, N ; Sharif University of Technology
    Elsevier Ltd  2019
    In this study, the optimum curing temperature and alkaline solution-to-binder (S:B) ratio of geopolymer mortars based on waste ceramic powder (WCP) were investigated. For this purpose, mixes with S:B ratios of 0.4–0.7 were prepared and cured at 60, 75, 90, and 105 °C. The density, compressive and flexural strengths were measured at 3, 7, 14, and 28 days. Higher S:B ratios enhanced the flow of the fresh mortar. The optimum mortar was obtained for S:B ratio of 0.6 and curing temperature of 90 °C. The SEM analysis revealed that the optimal mix had a dense matrix with minimum pores. © 2019 Elsevier Ltd  

    Synthesis and Characterization of Nanodiamond/Epoxy Nanocomposites

    , M.Sc. Thesis Sharif University of Technology Aris, Atousa (Author) ; Shojaei, Akbar (Supervisor) ; Bagheri, Reza (Co-Advisor)
    In recent years, it has been interesting to to use nanodiamond (ND) in oreder to improve mechanical and electrical properties. Producing it in very low dimensions, make it more important to treat ND surface proportional to its application. Hence, with knowledge of influence of ND and its functional groups on curing process, in present research,carboxylic acid and amine were settled on its surface and in addition to untreated ND, they were dispersed in DGEBA epoxy as a reinforcement. Afterward, by adding triethylenetetramine kinetic cure of nanocomposites were investigated. For this purpose, conversion was determined using heat flow of reaction and then activation energy was calculated.... 

    Polyamide membrane surface and bulk modification using humid environment as a new heat curing medium

    , Article Journal of Membrane Science ; Volume 523 , 2017 , Pages 129-137 ; 03767388 (ISSN) Karimi, H ; Bazgar Bajestani, M ; Mousavi, S. A ; Mokhtari Garakani, R ; Sharif University of Technology
    Elsevier B.V  2017
    Heat curing was devised in temperature-controlled steam and water environments to synthesize reverse osmosis (RO) polyamide (PA) membrane. The effect of new curing media on the physicochemical properties and RO performance of the synthesized polyamides was fully investigated using X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared (ATR-IR), scanning electron microscopy (SEM), atomic force microscopy (AFM), and water drop contact angle. The results show a reduction in amide linkage content on the surface of the steam-cured polyamide and surface and bulk of the water-cured polyamide. Additionally, it was revealed that heat curing in the humidity-controlled environment... 

    Production of chlorosulfonated rubber from postconsumer polyethylene and evaluation of produced rubber properties

    , Article Polymer - Plastics Technology and Engineering ; Volume 47, Issue 5 , 2008 , Pages 508-514 ; 03602559 (ISSN) Moradi, A ; Ramazani, S. A. A ; Shahrokhi, M ; Sharif University of Technology
    In order to convert the postconsumer polyethylene to a valuable product, chlorosulfonation of virgin and highly degraded polyethylene has been carried out in the solution phase under atmospheric pressure. Produced chlorosulfonated polyethylene samples from virgin and degraded HDPE are compounded and cured at different temperatures and their mechanical properties are determined. The results show that degradation of used polyethylene does not have noticeable negative effects on the final mechanical properties of produced chlorosulfonated rubbers. Therefore, it can be concluded that chlorosulfonation can be considered as an effective new method for polyolefin recycling  

    Analysis of the sedimentation process in reactive polymeric suspensions

    , Article Chemical Engineering Science ; Volume 61, Issue 23 , 2006 , Pages 7565-7578 ; 00092509 (ISSN) Shojaei, A ; Arefinia, R ; Sharif University of Technology
    Sedimentation of particles can undermine the uniformity of the product in the manufacture of the particle-filled composites. An adequate mathematical description of the sedimentation process could be helpful for providing necessary information concerning the dominant parameters and can give an insight for the process designer to prevent such an undesirable phenomenon in composite production. The present article deals with the mathematical modeling of settling particles during curing of polymer matrix composites. The sedimentation process is described by the mass conservation law for particles. Since the viscosity of the suspending polymer increases as a result of curing process, a new model... 

    Innovative semi-analytical methodology to predict automobile body temperature distribution in the curing ovens

    , Article Heat Transfer Engineering ; Volume 33, Issue 2 , Jun , 2012 , Pages 109-117 ; 01457632 (ISSN) Hanafizadeh, P ; Sajadi, B ; Saidi, M. H ; Sharif University of Technology
    In automobile painting industries, new automobile body products frequently should be tested in order to determine the actual thermal behavior of a paint curing process before starting mass production. During the hardening processes of dipped paint coating, applied in the electrophoretic enameling process, or top paint coating, applied in the final coating process, the automobile body must be warmed up according to the specific paint manufacturer curve. Consequently, prediction of car body temperature during the curing process may be vital in the design and performance analysis of the paint ovens. Numerical simulation of these processes may reduce expensive and time-consuming experimental... 

    Design and Evaluation of Cold In-Place Recycling with Emulsion

    , M.Sc. Thesis Sharif University of Technology Bazrafshan Moghadam, Bahador (Author) ; Tabatabaee, Nader (Supervisor)
    Although there are several popular and standardized mix design methods for hot-mix asphalt, there is no universally accepted mix design method for cold in-place recycling (CIR). The varieties of recycling machinery, materials, quality control limitations, etc. have contributed to this problem. Most of CIR laboratory mix designs are based on 4-inch molds and maximum aggregate size of 1inch. The use of single unit train, which is the most common machinery used for CIR, results in poor control of aggregate gradation, especially when distresses such as fatigue cracking exist. This may lead to presence of aggregate sizes larger than 1 inch. In this case the use of 4-in mold is no longer... 

    Application of ultrasonic models for investigating the properties of the interface between roller compacted concrete (RCC) layers

    , Article NDT and E International ; Volume 124 , 2021 ; 09638695 (ISSN) Ashkar, M ; Toufigh, V ; Ghaemian, M ; Azizmohammadi, M ; Sharif University of Technology
    Elsevier Ltd  2021
    In this paper, a comprehensive set of linear and nonlinear ultrasonic techniques was performed to investigate the properties of the interface between the roller-compacted concrete (RCC) layers. The effect of different time intervals between the pouring of each layer, cement content of concrete and bedding mortar, and various curing periods on RCC specimens were studied in this research. In linear methods, the interlayer led to velocity dispersion and attenuation phenomena except for the inherent inhomogeneity of specimens. The nonlinear parameters showed a general upward at the earlier ages, while the linear methods did not show an apparent regularity. The ultimate strength results were then... 

    Prediction and optimization of cure cycle of thick fiber-reinforced composite parts using dynamic artificial neural networks

    , Article Journal of Reinforced Plastics and Composites ; Volume 31, Issue 18 , September , 2012 , Pages 1201-1215 ; 07316844 (ISSN) Jahromi, P. E ; Shojaei, A ; Reza Pishvaie, S. M ; Sharif University of Technology
    Curing of thermoset-based composites experience substantial temperature overshoot, especially at the center of thick parts and large temperature gradient exists through the whole part due to large amount of heat released and low conductivity of the composite. This leads to non-uniformity of cure, residual stress and consequently composite cracks and possibly degradation of the polymer. The scope of this work is to optimize the cure cycle in order to improve the properties and gaining a relatively uniform part of composite, using trained recurrent artificial neural networks purposed for speeding up the repetitious model re-calls during the optimization process. Numerical results obtained... 

    Small-strain shear modulus of cement-admixed kaolinite

    , Article Geotechnical and Geological Engineering ; Volume 30, Issue 1 , Oct , 2012 , Pages 163-171 ; 09603182 (ISSN) Bahador, M ; Pak, A ; Sharif University of Technology
    An experimental study is conducted to measure small-strain shear modulus of clay-cement mixture using bender element apparatus setup in a triaxial cell. Bender element tests were conducted on cement-treated soils and the results were analyzed to study the variation of shear modulus properties of soil specimens at different cement contents, confining pressures, curing times, and compaction moisture contents. Based on the obtained results increasing the cement ratio has a significant effect on the small-strain shear modulus of the treated soils, and this effect signifies with increasing the moisture content and curing time. Rates of shear modulus enhancements due to cement content, curing... 

    Effect of system of initiators on the process cycle of nonisothermal resin transfer molding - Numerical investigation

    , Article Composites Part A: Applied Science and Manufacturing ; Volume 41, Issue 1 , 2010 , Pages 138-145 ; 1359835X (ISSN) Shojaei, A ; Farrahinia, H ; Pishvaie, S.M.R ; Sharif University of Technology
    The role of initiators with different reactivities on the process cycle of nonisothermal resin transfer molding (RTM) was examined using the numerical simulation. A new process model was developed based on flow, heat and mass transfer equations combined with an appropriate mechanistic kinetics model which elucidates the functions of the initiators in the system. The process cycle of RTM with both single initiator and dual-initiator (combination of two initiators) was analyzed. The numerical simulations revealed that the single initiator with high reactivity reduces the cycle time, but there is a risk of incomplete mold filling and nonuniform temperature distribution. For dual-initiator...