In this work, we investigated the effect of carbon nanotubes addition and agglomeration formation on the mechanical and electrical properties of CNT–polymer-based nanocomposites. Six specimens with carbon nanotubes (CNTs) fractions of 0%, 0.5%, 1%, 2%, 4% and 5% were manufactured and characterized by dynamic mechanical analysis (DMA) and four-probe method. The stress–strain curves and electrical conductivity properties were obtained. Scanning electron microscopy (SEM) was used to characterize both agglomeration and porosity formation. By employing micromechanics, through representative volume element (RVE), finite element analysis (FEA) and resistor network model (RNM), the Young’s modulus and electrical conductivity values were calculated. The samples’ elastic moduli showed an increment, reaching the maximum value at a CNTs fraction of 2%, thereafter an adverse effect was caused in the high CNT percentage samples. The final electrical conductivity seemed greatly altered with the addition of CNTs, reaching the percolation threshold at 2%. The unavoidable formation of CNT agglomerates appeared to influence the final physical properties. The CNT agglomerates adversely affect the mechanical performance of high-CNT-percentage samples. Conversely, an exponential increment in the electrical conductivity was presented as the agglomerates formed networks allowing the transport of electrons through the tunnelling effect. These phenomena were experimentally and numerically confirmed, showing a good correlation.
In this study, indentation tests of graphene-based polymer nanocomposites were carried out to determine the local elastic mechanical properties. The samples consist of epoxy matrix with graphene additives. Additives were added at levels of 0% as a control, 0.5%, 1%, 2.5%, 5% and 10% by weight. The local elastic properties such as moduli and hardness were calculated. After each indentation, the prints were characterized using scanning electron microscopy (SEM). It seems that the local mechanical properties of nanocomposite samples were improved as the amount of nano-additives increased. Based on the curve displacement and surface imaging, we can conclude that the nano-additives influenced the overall plastic mechanical behavior of the samples. For simulating micro-indentation test, a finite element analysis model was developed using ABAQUS software and compared to experimental tests. Good correlation was observed.
In this study, graphene was prepared using electrochemical exfoliation method. Numerical study of the exfoliation process of graphite was carried out using COMSEL Multiphysics 5. The homemade graphene was characterized using various microscopy, spectroscopy and X-ray diffraction techniques. The prepared graphene oxide consists of few layers of graphene. The numerical study showed that the concentration of sulfate anions was transported through graphite rod in the range (9.77 × 10 −7 -4.58 × 10 −5 ) mol/m 3 and stresses distribution which resulted from sulfate anions interaction along the graphite rod in the range (3.43 × 10 −8 -5.77 × 10 −7 ) N/m 2 .
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