| Problems arising from elastic instabilities and excessive vibrations of large and light weight flexible composite plates seriously limit their use in critical applications such as space structures, satellites and helicopters. However, such problems can be avoided by actively controlling the static and dynamic characteristics of these plates through the use of shape memory fibers, made of a nickel-titanium alloy (NITINOL), which are embedded in the composite fabric of the plates. These fibers can generate very high forces when heated above their phase transformation temperature. The resulting forces can increase the elastic energy and the stiffness of the composite plates in such a way that increases their critical buckling loads and shifts their vibration modes away from the excitation frequency band in order to avoid undesirable vibrations. Particular emphasis is placed, in this dissertation, on studying the interaction between the static, dynamic and thermal characteristics of NITINOL-reinforced composites plates especially during the activation and deactivation of the Shape Memory Effect. Mechanical and thermal finite element models are developed to investigate this interaction for plates subject to different loading and boundary conditions. The predictions of these models are validated experimentally and are found to be in close agreement with the measurements. |
