THE ACTIVE BUCKLING CONTROL, OF SOME COMPOSITE COLUMN STRIPS USING PIEZOCERAMIC ACTUATORS

The overall flexural buckling control of composite column strips using piezoceramic actuators is examined in this paper. The buckling control is investigated through the use of induced strain actuation associated with the piezoelectric effect and in conjunction with a closed-loop control system. Three column strip specimens have been fabricated from commercially available carbon-epoxy pre-impregnated sheets. The layup configurations are [90(2)/0](s), [+/-45/0](s), and [90(2)/+/-45](s). The length and width of each test specimen is 280 mm and 35 mm respectively. After manufacture of the composite column strips, piezoceramic actuators were surface bonded at their mid-heights on both sides of the column. Due to imperfections in the material, and of a geometrical nature, the composite column strips, with inactivated piezoceramic actuators, will deflect from the onset of loading and reach an ultimate load capability at high deflection levels. As a result of the presence of imperfections, this ultimate load will be less than the critical buckling load of the ideal structure. By applying a controlled voltage to the actuators a reactive moment will be induced at the column centre thereby removing the lateral deflections and enforcing the column to behave in a perfectly straight manner. An exact theoretical buckling analyses is outlined. This is used to evaluate the critical buckling loads of the individual composite test specimens. The test procedure is outlined and load-deflection plots, obtained with and without active control, are presented. The composite column strips with active control are shown to clearly demonstrate an increase in axial compressive load capacity compared to those without control. For the layup configurations considered, increases in load carrying capability are of the order of 19.8%-371%.