NITINOL-REINFORCED PLATES .3. DYNAMIC CHARACTERISTICS

The dynamic characteristics of NITINOL-reinforced composite plates are controlled by heating sets of NITINOL fibers embedded inside these pl ates. The activation of the shape memory effect of these NITINOL fiber s increases the elastic energy, enhances the stiffness of the composit e plates and modifies their modal characteristics. One of the objectiv es of the resulting modal modification is to shift the modes of vibrat ion of the plates away from the excitation frequencies in order to avo id undesirable resonances. In this way, the modal characteristics can be tailored in response to the external disturbances acting on the pla tes. The classical finite element approach is used to form the equatio ns of motion of the assembly of NITINOL-reinforced plate elements and the appropriate boundary conditions are then applied. The solution of the eigenvalues of the resulting homogeneous equations gives the natur al frequencies of the NITINOL-reinforced plate as influenced by the pr operties of the composite matrix and the NITINOL fibers. It is importa nt to note that these properties are influenced by the temperature dis tribution inside the composite plate which is developed by virtue of a ctivating and de-activating the NITINOL fibers. Emphasis is placed on the effect of intentional electrical heating of a selected subset of t he NITINOL fibers on the overall dynamics of the plates. The effect of the associated thermal energy propagating through the composite on th e unintentional thermal activation of additional subsets of the NITINO L fibers is accounted for. Such an effect is not only significant, but also essential to the thorough understanding of the operation of the NITINOL-reinforced plates.