Vibrational analyses of glass-reinforced polyester composite plates reinforced by a minimum mass central stiffener

Thin plates are extensively used in many fields of engineering, from ship superstructures, to the high technology of the modern aerospace industries. Flat plates which are incorporated into certain types of these structures have to be stiffened when the breadth/thickness ratio of the plate exceeds certain limits. In some structures, the addition of stiffeners to the plate would introduce a weight penalty. Consequently, it would be advantageous to keep the total mass of the plate constant by taking a thin uniform layer of constant thickness from the plate and forming it into one or several stiffeners. This would result in a considerable increase in the natural frequencies of the plate structure and a reduction of its vibration amplitudes whilst retaining the same mass of the plate system. Top-hat and rectangular stiffeners with different cross-sectional configurations have been investigated in order to increase the structural dynamic efficiency of these plates. The variables of the cross-section of the stiffeners were width and thickness but the mass of these stiffeners was kept constant.