In this paper, the theoretical predictions of mechanical properties of functionally graded and uniform distributions Epoxy/clay nanocomposites are presented. The specimens were prepared for uniformly distribution of nanoclay with different nano particles weight percent (pure, 3 wt%, 5 wt% and 7 wt%) and functionally graded distribution. The distribution of nanoparticles has been investigated by Field Emission Scanning Electron Microscopy (FESEM). For uniformly distribution of nanoclay, it is shown that there is no sign of the agglomerates found via FESEM imaging which can address well the distribution of nanoclay particles in epoxy. In addition, for functionally graded distributions, it is found that dispersion of nanoclays vary smoothly and continuously from one surface to the other one. The mechanical properties have been determined by simple extension tests. The results of extension tests show that elastic modulus begins to increase up to 5 wt% of nanoclay and then decreases. So, for functionally graded distribution, the elastic modulus is generally larger than the corresponding values for uniform distribution of nanoclay. The theoretical predictions of Young’s modulus for functionally graded and uniform distributions nanocomposites are calculated using a genetic algorithm procedure. The formulation for Young modulus includes the effect of nanoparticles weight fractions and it is modified for functionally graded distribution. To investigate the accuracy of the present theoretical predictions, a comparison is carried out with the experimental results. It is found that the results obtained from the theoretical predictions of genetic algorithm procedure are in good agreement with the experimental ones. Manuscript profile

This paper deals with free vibration of epoxy/clay nanocomposite beams for functionally graded and uniformly distributed of Nanoclay with simply supported conditions at both ends. The specimens were prepared for uniformly distributed of Nanoclay with different Nanoparticles weight percent (pure, 3 wt%, 5 wt% and 7 wt%) and functionally graded distribution. To apply the model of theoretical predictions for the Young modulus, the genetic algorithm procedure was employed for functionally graded and uniformly distributed epoxy/clay nanocomposites and then were compared with the experimental tensile results. The formulation for Young modulus includes the effect of nanoparticles weight fractions and it is modified for functionally graded distribution to take into account the Young modulus as a function of the thickness coordinate. The displacement field of the beam is assumed based on the first order shear deformation beam theory. Applying the Hamilton principle, the governing equations are derived. The influence of nanoparticles on the free vibration frequencies of a beam is presented. To investigate the accuracy of the present analysis, a compression study is carried out with the experimental free vibration results. The results have shown that there is high accuracy for the genetic algorithm procedure for theoretical predictions of the Young modulus and the free vibration frequencies for uniform distribution are generally lower than the corresponding value of the functionally graded distribution. Manuscript profile

In this research, the impact behavior of nanocomposite sandwich panels with epoxy/fiberglass/nanosilica face sheet were assessed by the finite element method. In the first step, the mechanical properties of the nanoparticle-containing composite should be obtained. A unit cell of fabric was designed in Catia software and placed within the designed polymeric matrix. The mechanical properties of this unit cell were defined as a new matrix and the nanoparticles were randomly dispersed in the new matrix using a Python code. The elastic properties of the modeled nanocomposite were obtained using Abaqus software via applying periodic boundary conditions based on the mean volumetric stress. In the next step, the sandwich structure was subjected to impact loads at various speeds and contact force-time diagrams were plotted using Abaqus software. The modeled results were compared with the known experimental data which showed a high accuracy in predicting the mechanical properties and impact behavior of the nanocomposite sandwich structures. Manuscript profile

In this research, two methods of conventional Friction Stir Welding (FSW) and two-pass friction stir welding have been used to weld AA6061-T6 alloy parts with a copper interlayer (copper foil. Based on the results, it was determined that the number of welding passes, the presence or absence of copper foil as an interlayer, the number of welding passes, the direction of tool rotation and the direction of tool movement in the second pass strongly affect the strength and ductility of FSW. According to the results, the highest tensile strength and ductility belong to TP-D(Two-Pass, type D), TP-B(Two-Pass, type B), TP-C(Two-Pass, type C), TP-A(Two-Pass, type A), CF-Cu and CF(Conventional FSW) samples, respectively. The mentioned samples have growth of 21, 29, 45, 36 and 58% respectively compared to the CF sample. The highest strength growth was related to the TP-D sample, which experienced a 58% increase in tensile strength compared to the CF sample. The tensile strength efficiency of this sample is 89.3% compared to the base metal. The highest increase in ductility was related to the TP-D sample, which experienced a 35% increase in ductility compared to the CF sample. The ductility efficiency of this sample is 81.1% compared to the base metal. Manuscript profile

The present study investigated the effect of using tools with tapered pins in Friction Stir Welding (FSW) of AA6061-T6 aluminum alloy. Two techniques named conventional FSW and Refill Friction Stir Welding (RFSW) were used for this purpose. Five tools with different tapered angles (0, 5, 10, 15, and 20 degrees) were used. To study the mechanical properties, tensile, three-point bending, and Vickers microhardness tests were performed. Macrographic and microstructural tests were also used to investigate the metallurgical properties of the welded samples. Based on the results, it was found that the key factors determining the ductility and strength of the welded specimens are the type of welding process (conventional FSW or RFSW) and the geometry of the tool pin (straight or tapered pin). Furthermore, it was found that all specimens welded by RFSW have higher tensile strength and elongation than the samples welded by conventional FSW. Manuscript profile