توجه: محتویات این صفحه به صورت خودکار پردازش شده و مقاله‌های نویسندگانی با تشابه اسمی، همگی در بخش یکسان نمایش داده می‌شوند.
۱Effects of adhesive thickness and its dynamic disbond on fatigue performance of cracked aluminium panels repaired with adhesively bonded composite patches
نویسنده(ها): ،
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۸
In this study the fatigue crack growth of cracked aluminum panels repaired with singleside composite patches with respect to the effect of adhesive thickness is investigated in mode I condition. contrary to the previous studies initial and permanent debonding between adhesive layer and aluminum panel were not considered and the dynamic disbond effects simultaneous with fatigue crack growth were considered.For this purpose numerical finite element analysis was carried out by developing a three–dimensional finite element model using the finite element commercial software (ANSYS) in order to evaluate real crack–front shape and also fatigue crack life and results compared with experimental data.Crack growth has been considered non–uniformly to obtain precise crack–front shape.The results show considerable improvement in fatigue crack growth life (98.5% by considering the effect of dynamic disbond and 161% without considering the effect of dynamic disbond) as compared to unrepaired condition. A new parameter is introduced to indicate the effect of dynamic disbond more accurately named (DA).In this study for obtaining mechanical fracture parameters (SIF, J) energy method based on J–integral has been used<\div>

۲Multiwall Carbon Nanotube Application in Co–cured Adhesive Joints ofE–glass \epoxyLaminates and Al– 2024–T3
اطلاعات انتشار: دومین کنفرانس بین المللی کامپوزیت، سال
تعداد صفحات: ۶
In this manuscript, the effects of dispersed multiwall carbon nanotubes (MWCNT) and functionalized multiwall carbon nanotubes in epoxy resinis investigated in terms of bonding strength. Reinforced epoxy, with various weight fractions of MWCNT and functionalized MWCNT was employedto fabricateco–cured single lap joint specimens ofE–glass\epoxy and alloy aluminum 2024–T3 adherents. Average shear strength were measured experimentally as a representative of bonding strength. Considerable enhancement in bonding performance was observed when the pure MWCNT were used and it significantly increased with increasing the weight fraction of carbon nanotubes. Whereas,bonding performance was decreased by usingfunctionalized MWCNT in epoxy adhesive.<\div>

۳Experimental Investigation On GFRP Composites Under High And Low Velocity Impact
نویسنده(ها): ، ،
اطلاعات انتشار: کنفرانس بین المللی فرآورش پلیمرها، سال
تعداد صفحات: ۴
Impact response of glass fiber reinforced plastic (GFRP) composites is of interest in military, marine and structural applications. The overall objective of this work was to investigate behavior of GFRP composites of constant thicknesses under high and low velocity impact . 0, 10, 20 and 30 (wt %) E–glass chopped strand fibers were incorporated into polypropylene using an internal mixer and all of the specimens were injection molded into square plates of size 120×120×2 mm and rectangular impact bars in an injection molding machine. Izod impact tests were performed using an Izod impact tester on specimens with V–notches. The values of the notched Izod impact energy were obtained from each group of five specimens. A single stage gas gun in velocity range of 20–150 m\s and harden steel hemispherical tip projectile with diameter of 8.1 mm and weight of 11.34 g, was used to conduct high velocity impact tests. In all of GFRP composite specimens, energy absorption and ballistic limit velocity showed better performance than specimens without glass fiber. Moreover results showed higher values for specimens containing 20 (wt %) glass fiber. In the other hand energy absorption and ballistic limit of GFRP composites was found to be strongly affected by fiber weight fractions.<\div>

۴ab initio Molecular Dynamics Simulation on the Hydrogen Adsorption on Pt–dop Graphene
نویسنده(ها): ، ،
اطلاعات انتشار: اولین همایش ملی نانومواد و نانو تکنولوژی، سال
تعداد صفحات: ۶
In this work, the decoration of a graphene sheet with Pt is considered as a hydrogen storage material by means of density functional theory calculations. Various active sites were considered for H2 adsorptionon the pristine graphene sheet. After full structural relaxation of the considered systems it was found that H2 molecule physisorbed on the hollowsite of the C ring of graphene surface. However H2 adsorption capability of Pt attached graphene found to be significantly enhanced. The calculatedadsorption energy for two considered systems are –0.12 and –2.46 eV, respectively. ab initio MD simulation carried out at room temperature indicate that after 130 fs, H2 molecule adsorbed on the Pt atom then dissociated to two H atoms which indicate that this material might be a superior media for hydrogen adsorption in fuel cell application<\div>

۵Effect of Melt Mixing Processing conditions on the Flexural andMorphological Properties of Polypropylene Reinforced with MesoporousSilica\Hydroxyapatite Nanoparticles
نویسنده(ها): ، ، ،
اطلاعات انتشار: کنفرانس دو سالانه بین المللی مکانیک جامدات تجربی، سال
تعداد صفحات: ۶
The polypropylene (PP) nanocomposite reinforced with the composite of mesoporous silica and hydroxyapatite (MH), were prepared by melt mixing in an internal mixer and melt extrusion in a twin screw extruder. The influence of processing parameters on the flexural performance of the nanocomposite was studied by varying the mixing temperature and rotor speed of internal mixer. Maleic anhydride grafted polypropylene (PP–g–MA) was used as compatibilizer. The nanocomposites were characterized by performing flexural testing and Scanning Electron Microscopy (SEM) analysis. It was found that PP\MH prepared by two techniques were effectively enhanced the flexural propertiesof neat PP. The enhancement of flexural strength was about 33% by melt extrusion and 17.8% by melt mixing compared with neat PP. Therefore, by incorporating MH nanoparticles in PP, we could achieve a new hybrid nanocomposite with high flexural properties. Also, the optimum temperature of 180°C and rotor speed of 100 rpm obtained and applied to the extruder to achieve higher flexural properties. A higher shear rate of the twin screw extruder and more efficient sol–gel reaction led to better dispersion and higher flexural properties. From SEM images, it was observed that nanoparticles were distributed reasonably uniformly indicating a good dispersion of nano phase in the PP matrix by using extruder.<\div>

۶Effect of Mesoporous Silica and Hydroxyapatite Nanoparticles on the TensileBehavior of Polypropylene: Experimental Studies and Simulations
نویسنده(ها): ، ، ،
اطلاعات انتشار: کنفرانس دو سالانه بین المللی مکانیک جامدات تجربی، سال
تعداد صفحات: ۸
This study focuses on the effect of incorporation of two different types of nanomaterials, mesoporous silica (MCM–41), Hydroxyapatite (HA) into the polymer matrix on morphology and tensile properties of polypropylene (PP). PP\MCM–41 and PP\HA nanocomposites have been prepared by melt mixing in a twin–screw extruder. The results of tests showed that tensile strength is increased by 6.47% and 26.57% by using MCM–41and HA nanoparticles rather than neat PP, respectively. The MCM–41 filler leads to lower tensile properties comparing to the HA nanoparticles, but the advantage of MCM–41 filler than HA particles is the porous structure and high surface area of MCM–41 particles makesavoids agglomerations even at high weight percentage levels. Moreover, to investigate the tensile behavior of nanocomposites using constitutive models, applicability and best fit of three different hyperelastic models including Van der Waals, Ogden and Marlow against experimental data were studied using the commercial software ABAQUS\CAE. The performed simulations produced good results for uniaxial tensile loading. SEM observations showed that the nanomaterials were well dispersed in the polymer matrix and the enhancement of the interface between the matrix and fillers were obtained by nanoparticles.<\div>

۷Effects of SiO2 and TiO2 nanoparticles on the mechanical and tribological behaviors of epoxy resin
نویسنده(ها): ، ،
اطلاعات انتشار: کنفرانس دو سالانه بین المللی مکانیک جامدات تجربی، سال
تعداد صفحات: ۶
In this manuscript, mechanical and tribological behaviors of SiO2\epoxy, TiO2\epoxy nanocomposites are investigated under scratch and nano indentation loading by using Hysitron nano indentation testing instrument. For each nanocomposites 5 wt. % of nanoparticles were added to the epoxy and experimental results showed that adding nanoparticles to resin increases its hardness and elastic modulus. It is also indicated that addition of particles causes in a decrease of coefficient of friction and scratch depth of the specimens. Furthermore, the specimens containing the nano particles showed less surface deformation in comparison with the neat epoxy resin under the same specified external point loading. Specifically, the SiO2\epoxy specimens showed least deformation, followed by TiO2\epoxy Nano composites. The result of scratch and indentation tests and AFM images showed that the penetration depth decreases by adding nanoparticle. For instance the indentation test of SiO2\Epoxy shows 42% decrease in the penetration depth compared with the neat epoxy. Also, the scratch test of SiO2\Epoxy shows 75% decrease in comparison with the neat epoxy. The results showed that TiO2\epoxy nano composites had a tendency to decrease the coefficient of friction.<\div>

۸The Effect of Mixing Temperature and Mixing Technique on the MechanicalProperties of Polypropylene – Mesoporous Silica\Hydroxyapatite HybridNanocomposites
نویسنده(ها): ، ، ،
اطلاعات انتشار: کنفرانس دو سالانه بین المللی مکانیک جامدات تجربی، سال
تعداد صفحات: ۶
This work focuses on the influence of mixing temperature and effectiveness of different mixers on the tensile and flexural properties of polypropylene (PP) and PP\Mesoporous silica–Hydroxyapatite (MCM–41–HA (MH)) hybrid nanocomposites. The other important study is the enhancement of mechanical properties of PP by adding MH nanoparticles. How the mixing efficiency affects the dispersion of nanoparticles was investigated using two different mixing devices, an internal mixer and a twin screw extruder. In the first step, neat PP and hybrid nanocomposites based on PP, containing maleic anhydride grafted polypropylene (PP–g–MA) and MH were prepared in the different mixingtemperatures with using the melt intercalation technique in the internal mixer. Tensile and flexural tests were performed to evaluate the mechanical characteristics (Young’s modulus, tensile strength, flexural strength and strain at rupture) of neat PP and PP\MH hybrid nanocomposites. Results showed that the shear stress and distribution process of nanoparticles have the main effect on the mechanicalproperties of nanocomposites that melt mixed in the internal mixer. Also, the optimum mixing temperature of 180 °C and mixing time of 3 minutes were found and applied to the extruder to achieve better mechanical properties. Results showed that a twin screw extruder is more efficient in breaking down the particles of MH in nano scale building blocks than an internal mixer. Because A higher shear rate of the twin screw extruder and more efficient sol–gel reaction led to better dispersion and higher mechanical properties. From SEM images, it was observed that nanoparticles were distributedreasonably uniformly indicating a good dispersion of nano phase in the PP matrix by using extruder.Moreover, the mesoporous structure and high surface area of MCM–41 particles and also high rigidityand large aspect ratio of HA molecules provided the fine mechanical properties for PP\MHnanocomposites. Approximately 16%, 29%, 43% and 42% increases in tensile strength, tensilemodulus, flexural strength and flexural modulus were observed for samples, respectively.<\div>
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