The paper describes a model to calculate the transmission loss of both curved laminate and sandwich composite panels within statistical energy analysis (SEA) context. The vibro-acoustic problem is developed following a wave approach based on a discrete lamina description. Each lamina is considered to consist of membrane, bending, transverse shearing and rotational inertia behaviors. Moreover, the orthotropic ply angle of each lamina is considered. Using such a discrete lamina description, the dispersion behaviors of the panel are correctly represented. Using the dispersion curves, the radiation efficiency, the modal density, as well as, the nonresonant and the resonant transmission are computed. Moreover, expression for the evaluation of the ring frequency and the critical frequencies of such panels is given. The described model is shown to handle accurately, both laminate and sandwich composite shells. Additionally, a transmission loss test is presented to confirm the validity of the presented model.
The objective of this research project is divided in four parts: (1) to design a piezoelectric actuator-based de-icing system integrated to a flat plate experimental setup and develop a numerical model of the system with experimental validation, (2) use the experimental setup to investigate actuator activation with frequency sweeps and transient vibration analysis, (3) add ice layer to the numerical model and predict numerically stresses for different ice breaking with experimental validation, and (4) bring the concept to a blade structure for wind tunnel testing. This paper presents the first objective of this study. First, preliminary numerical analysis was performed to gain basic guidelines for the integration of piezoelectric actuators in a simple flat plate experimental setup for vibration-based de-icing investigation. The results of these simulations allowed to optimize the positioning of the actuators on the structure and the optimal phasing of the actuators for mode activation. A numerical model of the final setup was elaborated with the piezoelectric actuators optimally positioned on the plate and meshed with piezoelectric elements. A frequency analysis was performed to predict resonant frequencies and mode shapes, and multiple direct steady-state dynamic analyses were performed to predict displacements of the flat plate when excited with the actuators. In those steady-state dynamic analysis, electrical boundary conditions were applied to the actuators to excite the vibration of the plate. The setup was fabricated faithful to the numerical model at the laboratory with piezoelectric actuator patches bonded to a steel flat plate and large solid blocks used to mimic perfect clamped boundary condition. The experimental setup was brought at the National Research Council Canada (NRC) for testing with a laser vibrometer to validate the numerical results. The experimental results validated the model when the plate is optimally excited with an average of error of 20% and a maximal error obtained of 43%. However, when the plate was not efficiently excited for a mode, the prediction of the numerical data was less accurate. This was not a concern since the numerical model was developed to design and predict optimal excitation of structures for de-icing purpose. This study allowed to develop a numerical model of a simple flat plate and understand optimal phasing of the actuators. The experimental setup designed is used in the next phase of the project to study transient vibration and frequency sweeps. The numerical model is used in the third phase of the project by adding ice layers for investigation of vibration-based de-icing, with the final objective of developing and integrating a piezoelectric actuator de-icing system to a rotorcraft blade structure.
The main objective of this paper is to present a theoretical approach to model the vibro-acoustic behavior of flat sandwich composite panels. Two models are studied: symmetrical laminate composite and sandwich composite panel. The theories are developed in a wave approach context. It is shown that a discrete layers sandwich composite panel modeling type leads to a 12th order relation of dispersion while a laminate composite panel modeling leads to a 6th order relation of dispersion. The two models give similar results at low frequencies but the modeling of a sandwich panel using the laminate panel theory leads to inaccuracies at high frequencies. The dispersion relations are first solved in the context of generalized polynomial complex eigenvalues problems. Next, the dispersion relations are used to derive the analytical expression of the critical frequencies and to calculate the natural frequencies of the panel. Using the dispersion relation’s solutions, the study is then focused on the numerical computation of the group velocity, the modal density and the total transmission loss.
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