Buckling analysis of mechanical structures is essential to insure stability under loading .Critical load of buckling refer to the maximum load can be withstood without losing of stability and avoid a catastrophic damage due to the collapse of columns .Improving of mechanical properties spatially those related with elastic behaviors of materials can lead to improving buckling since it can be raised the value of critical load. Nanotechnology is one of the modern methods which makes significant effects on the mechanical properties of materials. In the field of composite materials this technology leads to valuable improvements for the favorite properties. In this regard Nano composite materials are paid a spatial attention in research for the last decade. The main aim of the present work is to investigate the effect of Nano carbon weight fraction on buckling of the composite plate. Five samples of Nano composite plates were prepared and fabricated for experimental investigations .The plate samples are combined of woven reinforcement fiber and polyester matrix with Carbon .The weight fraction of Nano additives are 0 %, 0.5%, 1%, ,1.5 and 2%, of resin materials weight. To provide homogenous composite an ultrasonic homogenizer is utilized. The experimental work include buckling test for different Nano plates samples with simply supported at two ends and free at the other .Finite Element analysis was achieved via ANSYS R15.0 with proper elements ,meshing ,boundary condition and static analysis .It is found that increasing of Nano carbon weight ratio tends to increase critical load of buckling ,the maximum buckling load is at 2% wt ratio and the experimental results shows fair validation for the numerical analysis where the maximum error dos not exceeded 15% .

Pipes conveying fluid have significant applications in a wide range of industrial and engineering applications .Recently, this topic has been crystallized into a dynamical model for analyzing the fluid-structure-interaction (FSI) which has vast applications in aerospace ,aerodynamics, ship motion , medical engineering ..etcThe general solution for the vibration equation of conservative pipes conveying fluid is derived in this paper .From this solution the frequency and critical buckling velocity equations for pinned-pinned, clamped-pinned and clampedclamped pipes conveying fluid are obtained semi-analytically in terms of the pipe parameters.A new experimental approach for estimating buckling critical velocities from measuring several natural frequencies at relatively small flow rates is presented. The results show good agreement between the estimated and theoretical critical velocities in case of pinned-pinned and clamped-pinned pipes .However for clamped-clamped pipes the accurate estimation requires higher flow rates .This method can serve using a relatively low pump discharge and simple fluid circuit instead of high discharge pumps which demand complication in the fluid circuits.