محسن رضایی حسن آبادی

In this study, according to capability of magneto-rheological fluids to change the stiffness and damping of structure, they can be used in the core of sandwich panel. The studied sandwich panel is double curved with simply support boundary condition. In order to derive the governing equations of motion, an improved high order sandwich panel theory and Hamilton's principle are used for the first time. Then the effect of magnetic field on the frequency of the panel has been investigated. The effects of changing the geometric parameters such as aspect ratio, thickness of MR layer, radius of curvature and thickness ratio on the characteristics of vibration panel have been studied. The obtained results showed that the natural frequencies of panel increase by increasing magnetic field strength to Bs (saturation magnetic field). Also it increases by increasing the panel aspect ratio, and reduces by increasing the core thickness to panel thickness ratio. Likewise the obtained results showed that natural frequencies for the case of double curved panel are more than single curved and flat panels. Therefore, by changing these parameters, the natural frequency of the system, can be changed in the desired range, and also by having a controllable magnetic field in the system, the natural frequency of the system can be controlled.

In this study, free vibration and static bending analysis of curved sandwich panel with magneto-rheological (MR) fluid layer in sheets have been studied. Sandwich panel that is studied is double curved with simply support boundary condition and it is under bending load. In order to derive the governing equations of motion, an improved high order sandwich panel theory and Hamilton's principle are used for the first time. After comparing with similar results in the domain of this issue and ensure that the accuracy of the derived equations, the effect of magnetic field on the frequency of the panel has been investigated. The effects of magnetic field intensity and changing the geometric parameters such as aspect ratio, thickness of MR layer, radius of curvature and thickness ratio on the characteristics of vibration and deflection have been studied. In the free vibration analysis section, the obtained results showed that the natural frequency of panel increases by increasing the magnetic field, also increases by increasing the panel aspect ratio, and decreases by increasing the core thickness to panel thickness ratio. Likewise the obtained results showed that the natural frequenciy for the case of double curved panel is more than single curved and flat panel. In the static bending analysis section, obtained results showed that the natural deflection of the panel decreases by increasing the magnetic field, increases by increasing the radiuses of curvatures ratio, and increases by increasing the core thickness to panel thickness ratio. Therefore, by changing these parameters, the natural frequency and deflection of the system, can be changed in the desired range, and also by having a controllable magnetic field in the system, the natural frequency and deflection of the system can be controlled.

In this study, single-objective and multi-objective optimization of curved sandwich panel with composite face sheets and magneto-rheological core have been done to maximize the first modal loss factor and minimize the mass by using genetic algorithm. The studied sandwich panel was curved with simply support boundary condition. In order to derive the governing equations of motion, an improved high order sandwich panel theory and Hamilton's principle were used for the first time. The face sheet thickness, core thickness, fiber angles and intensity of the magnetic field have been considered as optimization variables. In single-objective optimization, the optimized values of variables were calculated. The results showed that the structures tend to have thick core and thin face sheets which seems physically true. As the magneto-rheological fluid placed in the core, it has a significant effect on the increasing of the modal loss factor. For the multi-objective optimization the Pareto front of optimal technique was presented. Then for the first time at this field, the set of optimal points are selected based on TOPSIS method and it was showed that in the case of similar size and mass, modal loss factor of double-curved panel is more than sigle-curved.