Dynamic analysis of Carbon Nanotube-Reinforced Piezoelectric Composite for Active Control of Smart Structures

Smart structures have a wide range of potential applications in aerospace engineering, such as vibration and noise suppression, shape adaption and aeroelastic control of lifting surfaces. Piezoelectric materials are largely used as smart materials due to the their capability to perform both as sensors and actuators. Composite structures embedded with piezoelectric materials confer the low density, superior mechanical and thermal properties of composite materials along with sensing and vibration control. The aim of this thesis is the study of the dynamic behaviour and vibration attenuation of carbon nanotube reinforced composite plates, integrated with piezoelectric layers at the bottom and top surfaces. Distribution of CNTs reinforcement may be uniformly distributed (UD) or functionally graded (FG) according to linear functions of the thickness direction. The material properties of both matrix and CNTs are obtained through a modified rule of mixtures approach. Plate is modeled acccording with the method of the power series expansion of the displacement components and the electric potential. Primary variable’s expansion order is considered as a free parameter of the model. Hamilton’s principle is employed to derive the governing equations in their weak form. The latter are written in terms of fundamental nuclei which are mathematically invariant with respect to both the expansion order and the kinematic description of the unknows. The free vibration analysis is carried out considering the full coupling between the electrical and mechanical fields. The approximated solution is obtained by using Ritz method based on highly stable trigonometric trial functions. Forced response is obtained through the state-space approach considering various dynamic load cases. The response of the plate is controlled through the dynamic velocity feedback control algorithm and a closed loop. The upper piezoelectric layer acts as actuators, while the lower one act as sensors. Corvengence and accurancy of the proposed formulation is investigated comparing results with those available in literature. The effect of significant parameters such as, volume fraction, CNTs distribution and boundary conditions, on the natural frequencies and both uncontrolled and controlled response, is discussed.