Composite structure vibration analysis using the finite element method

Abstract

The need of low‐frequency sonar transducers led to the concept of flextensional structure and, currently, promotes the use of composite materials. To design these transducers, a finite element modeling is very useful, because this method can accurately handle the various constituting parts as well as the radiation damping. The finite element code ATILA [J. N. Decarpigny et al., J. Acoust. Soc. Am. 78, 1499 (1985)] has been used to analyze various types of metallic shell flextensional transducers and, more recently, a special three‐dimensional composite finite element has been developed to take composite shells into account. This element is composed of unidirectionally reinforced lamina and various fiber orientations and materials can be used in the same element. The stiffness finite element matrix is calculated using equivalent elastic constants [S. W. Tsai, “Composite Design,” in Think Composites (Dayton, Ohio, 1985)] and a separate numerical integration in three directions for each lamina. This paper presents the element formulation and its tests. Comparison between numerical and experimental results for simple structures has allowed the determination of the physical model parameters. Then, the modeling of a flextensional shell has demonstrated the accuracy of this approach.