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Sandwich panels have high strength to weight ratio because of their special structure. The variables which are defined for designing sandwich panels should be determined with applying necessary strength and lowest weight. In this paper, the imperialist competitive algorithm (ICA) has been used for minimizing the weight of a sandwich panel with prismatic core based on yielding and buckling criteria. ICA is inspired of imperialist competitions and it is based on two special criteria as recruitment policy and stable imperialist competition. Arrays numbers, core and surface thickness and panel height are assumed as design variables for decreasing panel weight. The results were shown that core and surface thickness and the total height of panel has been increased by increasing loading for given number of arrays. Also the core and surface thickness has been decreased and the total height have been increased by increasing array number for a determined loading and so panel weight has been decreased. A panel with diamond core has highest structure efficiency. It was shown that ICA is useful and competitive than the other heuristic algorithms because of direct using of function values in some problems which was required to the total optimization.

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Since there are struggles with CNTs dispersion in the resin and production costs, synthesis and test of epoxy/carbon nanotube (CNT) nanocomposites is not economical. For this reason, simulation methods are proper techniques to predict mechanical properties of these nanocomposites. But the actual dimensions of CNTs and their length to diameter (aspect) ratio is a cause for concern in nano and micro scale finite element modeling. In this paper, different arrangements of CNTs in epoxy matrix have been presented using a beam element as a CNT and creating representative volume element of nanocomposite in micro scale. Effects of volume fraction, aspect ratio and wave effects of CNTs on nanocmposite effective elastic moduli have been investigated. The results show that this method eliminates the limitation of both micro and nano molding and simulates the real conditions of nanocomposites and can be used to examine the effects of geometric parameters in the effective moduli. On the other hand, the simulation results have a good agreement with experimental results.

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In the present study, shearing properties of sugar cane stems were determined at five moisture content levels (46, 54, 62, 70 and 78% wb), three shearing speed (5, 10 and 15 mm min^-1) and at ten positions on the stem. For measuring the shearing forces, the stems were severed by using a computer aided cutting apparatus. Decrease in moisture content of stem from 78 to 46% wb led to 16.3 and 16.7% decrease in the shearing strength and specific shearing energy, respectively. The maximum and average values of shearing strength of the two moisture contents were found to be 3.482 and 3.1 MPa, and the specific shearing energies were 112 MJ mm^-2 and, 102.6 MJ mm^-2, respectively. Both the shearing strength and the specific shearing energy were found to be higher in the lower region of the stem due to structural heterogeneity. Results showed that with the increase in shearing speed from 5 to 15 mm min^-1, shearing strength and the specific shearing energy increased 3.2 and 4.6%, respectively. The results of ANOVA indicated that effects of the mentioned factors were significant at 1% probability level. The shearing model assessment revealed that the third order polynomial model exhibited the best performance in fitting with experimental data and, by using this model, a significant correlation was found between shearing strength, specific shearing energy, and moisture content (R²= 0.989 and SE= 0.001). Also, a significant correlation was found between shearing strength, specific shearing energy, and shearing speed by using Hoerl model (R²= 0.989 and SE= 0.005).