Free vibration behavior of laminated composite stiffened elliptic parabolic shell panel with cutout

In this paper free vibration behavior of laminated composite stiffened elliptic parabolic shell has been analyzed in terms of natural frequency and mode shape. Finite element method has been applied using an eight-noded curved quadratic isoparametric element for shell with a three noded curved beam element for stiffener. Cross and angle ply shells with different edge conditions have been studied varying the size and position of the cutouts to arrive at a set of inferences of practical engineering significances.

Photonic Control of a Free-Floating Parabolic Membrane Shell

Communication antennas, optical mirrors, solar/optical reflectors, etc. often have the shape of parabolic shells or shells of revolution, due to their required focusing, aiming, or reflecting performance. In this paper, the wireless control of free-floating flexible parabolic shells using discrete photostrictive actuators is investigated. Parabolic shell of revolution is considered to be one of the most difficult geometry among all shell and non-shell structures. Because of this, an approximate way to estimate the dynamic behavior and light-induced control forces of a photostrictive coupled parabolic shell is presented. Based on the approximate spherical model, the effects of actuator locations as well as membrane and bending components on the control action are analyzed. The results obtained indicate that the control forces are location dependent. It is also shown by analysis that the membrane control action is much more significant than the bending control action. The validation of the approximate model is done by comparing the light-induced control forces of the photostrictive coupled shells obtained by the approximate equivalent spherical shell model and those obtained by the parabolic shell model. From the comparison, it can be concluded that there is only a slight difference between a spherical shell and a parabola for surface with an F/D (focal length to diameter ratio) of 1.00 or larger.

Wireless Control of Parabolic Shells Using Photostrictive Actuators

Photostrictive actuator, which can turn light energy into mechanical energy, is a new promising photoactuation technique for non-contact wireless active control of flexible structures. Optical mirrors, communication antennas, solar/optical reflectors, nozzles, rocket fairings, etc. often have the shape of parabolic shells or shells of revolution, due to their required focusing, aiming, or reflecting performance. In this paper, the active control of flexible parabolic shells using discrete photostrictive actuators is investigated. Parabolic shell of revolution is considered one of the most difficult geometry among all shell and non-shell structures. Because of this, an approximate way to estimate the dynamic behavior and light-induced control forces of a photostrictive coupled parabolic shell is presented. Based on the approximate model, the effects of actuator locations as well as membrane and bending components on the control action are analyzed. The results obtained indicate that the control forces are mode and location dependent. It is also shown by analysis that the membrane control action is much more significant than the bending control action. The validation of the approximate model is done by comparing the light-induced control forces of the photostrictive coupled shells obtained by the approximate equivalent spherical shell model and those obtained by the parabolic shell model.