This paper presents an analytical cum experimental study of using magnetostrictive actuators in conjunction with an extension-torsion coupled composite tube to actuate a rotor blade trailing edge flap to actively control helicopter vibration. Thin-walled beam analysis based on Vlasov theory is used to predict the axial force-induced twist and extension in the composite tube. [20/-70]2s graphite-epoxy as well as [20/-70]_s and [11]_2 kevlar-epoxy tubes were fabricated using an autoclave molding technique. The tubes were tested under static mechanical loads, and tip twist and axial extension were measured by means of a laser optical system and strain gages respectively. The tubes showed good correlation between theory and experiment for the external load case. The magnetostrictive actuator/composite tube systems were then assembled and tested. The [20/-70]2s graphite-epoxy tube system exhibited 0.03 degrees of tip twist in both tension and compression, while the [20/-70] _s kevlar-epoxy tube resulted in a tip twist of 0.089 degrees in tension and 0.102 degrees in compression. The [11]_2 kevlar-epoxy tube system generated the most twist, 0.19 degrees in tension and 0.20 degrees in compression. The kevlar-epoxy systems showed good correlation between measured and predicted twist values. Further parametric studies were then performed to determine the important design variables that would result in maximum induced twist and actuator force.
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