محمدرضا گل بهار حقیقی

ییIn this thesis, firstly, the free vibration of sandwich curved beams with CNTRC face sheets and porous core was studied. Then, the dynamic response analysis of sandwich curved beams with CNTRC face sheets and porous core under impact loading was investigated. The governing equations for curved beams were derived based on the two-dimensional elasticity theory by using Hamilton's principle. The layerwise finite element method (LFEM) and differential quadrature method (DQM) were used to discretize the free vibration governing equations of the curved beam in the thickness and longitude direction, respectively. Also, the equations of motion for curved beams under impact loading were discretized using LFEM in the thickness direction and finite element method (FEM) in the longitude direction. Newmark's time integration scheme was also employed to discretize the equations of motion in the temporal domain. In studying the influence of impact loading, Hertzian contact law was employed to model the contact force between the projectile and curved beam and Newton-Raphson's method was adopted to solve the related nonlinear equations. Extended rule of mixture was used to obtain the effective mechanical properties of the composite material in the curved sandwich beam face sheets. Also five profiles of carbon nanotubes distribution in curved beam face sheets were investigated. The convergence of the method was numerically demonstrated and its accuracy was shown by performing the comparison studies with existing results in available literature in this regard. After that, the numerical results were presented to study the effects of various profiles of the CNTs distribution in face sheets, different boundary conditions, length-to-thickness ratio, core thickness-to-sum of face sheets thicknesses ratio and opening angle of curved beam for vibration and dynamic analysis under impact loading for various projectile velocity. It was seen that the sandwich curved beams with carbon nanotube-