In this paper, the effect of addition of nanosilica on mechanical properties of pure epoxy and epoxy/fiberglass composite has been investigated. The epoxy/nanosilica composites and epoxy/fiberglass/nanosilica hybrid composites have been fabricated, and the Young’s modulus, tensile strength, yield stress and elongation at break have been determined by simple extension tests. The results show that by addition of 1 wt% of nanosilica in both types of composites, Young’s modulus, yield stress and tensile strength decrease and elongation at break increases. By increasing the nanosilica content, the Young’s modulus, yield stress and tensile strength increase and elongation at break decreases. Also, imperialist competitive algorithm is employed to model the mechanical properties as fourth degree polynomial functions. The accuracy of polynomial is maximized and coefficients are obtained. The results show 25.66%, 56.87% and 45.84% improvement in Young’s modulus, yield stress and tensile strength of pure epoxy, respectively. Also, 12.9%, 24.83% and 12.85% improvement in Young’s modulus, yield stress and tensile strength of epoxy/fiberglass composites, has been observed, respectively.

Friction stir welding (FSW) is a solid-state welding technique, which two workpieces join by pressure and large plastic deformation near their melting points. The tool offset, pin offset, and position of dissimilar alloys can highly affect the maximum temperature and heat distribution in FSW process. In current research, the effects of three mentioned variables on the maximum temperature of FSW of AA6061 and AA5086 alloys have been investigated. In this manner, Response Surface Methodology (RSM) as an auxiliary method has been used. The results show that pin offset is the most effective parameter affecting maximum achieved temperature. In all pin and tool offsettings, placing the harder alloy (AA6061) at advancing side results in more maximum temperature increment compared to the case which the harder alloy is at the retreating side.

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