Identification of local Young's Modulus and loss factor of curved beam by using an inverse method and a finite element operator

Composite materials, which provide high stiffness and light weight, are increasingly used in the aerospace and automotive industry. Fabrication of structural parts in composite materials involves manufacturing of the material and its shaping in a same process. The knowledge of the homogenized elastic and damping properties is useful to predict the dynamic behaviour of the structure. However, most characterization methods are only applicable to samples with relatively simple geometry and don't take the shape of the parts into account. Curvature effects have two main issues: the material properties depend on space and a coupling between flexural motion and tension/compression motion occurs. Identification of elastic and damping properties of vibrating structures is possible by a local inverse method inspired from the Filtered Windowed Inverse Resolution (RIFF) also called Force Analysis Technique (FAT). This method was developed for plane structures like beams and plates, where the equation of the motion is known analytically. The extension of this method by using a Finite Element operator (FE) is practicable. It allows to identify locally the properties of the material on a structure with complex geometry. These properties can depend on the local shape of the structure. This paper points out the potentiality of the RIFF method coupled with the FE method to characterize the properties of materials, for complex geometries. In this case, the method is developed on a curved beam, to identify the Young's Modulus and the loss factor in a large frequency band, for various degrees of curvature.