The dynamic stability of a composite plate with external electrorheological (ER) damper subjected to an axial periodic load is investigated. Electrorheological fluids are a class of smart materials, which exhibit reversible changes in mechanical properties when subjected to an electric field. As a result, the dynamic behavior of the structure is changed. The ER damper is used for suppressing the vibrations and improving the stability of the system. The Bingham plastic model is employed to express the behavior of the ER fluid. The finite element model of the structure is developed and constant acceleration average method is used to obtain the response of the system. Effect of different parameters such as the electric field, the orientation of the ER damper, the initial gap between the two electrodes of the ER damper and the stacking sequences of the plate on the first instability boundaries of the composite plate are investigated. Manuscript profile

The present paper investigates the advantages of a new class of composite grid structures over conventional grids. Thus far, a known grid structure such as orthogrid or isogrid has been used as an orthotropic layer with at most in-plane anisotropy. The present laminated grid is composed of various numbers of thin composite grid layers. The stiffness of the structure can be adjusted by choosing proper stacking sequences. This concept yields to a large variety of laminated grid configurations with different coupling effects compare to conventional grids. To illustrate the advantages of the laminated grids, the stiffness matrices and the bending response of the laminated and conventional grids are compared. Furthermore, a progressive failure analysis is implemented to compare the failure resistance of laminated and conventional grids. The results indicate that, thoughtful selection of stacking sequences of the laminated grid enhances the stiffness and response of the laminated grids without significant effect on the failure index. Manuscript profile