Determination of the in-plane elastic properties of the different layers of laminated plates by means of vibration testing and model updating

Layered materials are becoming increasingly important for the production of high-performance components and constructions. Their stiffness properties are fundamental to assess stress fields during design calculations. Numerous analysis techniques to identify the elastic properties of materials exist, but in the case of layered materials, these techniques usually yield properties that are ‘averaged’ over the thickness of the test specimen. To assess the in-plane elastic properties of each individual layer, a new non-destructive testing method is developed. The proposed method derives the material properties from the resonance frequencies of a number of freely suspended test plates. A multi-model updating routine is used for this purpose. Finite element models of the different test plates are simultaneously updated. Once the Finite element models reproduce the measured frequencies, the updating procedure is halted, and the material properties of the different layers can be retrieved from the Finite element modelʹs database. It is shown that the multi-model approach is necessary to ensure the uniqueness of the obtained properties.