VIBRATION FREQUENCY CONTROL OF A POLYMER BEAM USING EMBEDDED SHAPE-MEMORY-ALLOY FIBERS

The possibility to actively change the natural vibration frequencies o f a composite beam by. electrically activating a series of embedded sh ape-memory-alloy fibres is investigated. A model system composed of an epoxy matrix with prestrained shape-memory-ahoy fibres is used. The n atural frequencies of vibration of the composite are measured in a cla mped beam configuration. When electrically heated, the fibres undergo a reverse martensite to austenite transformation. Since this transform ation is restrained by the constraints of both the matrix and the clam ping device, a recovery force is generated. This force produces an inc rease of the natural frequency of vibration of the whole composite bea m. Vibration frequency changes of more than 50% are obtained. The glas s-to-rubber transition of the matrix affects the reversibility of the effect. The role of the matrix thermal expansion is discussed.