Material characterization for orthotropic shells using modal analysis and Rayleigh-Ritz models

Using the method of Bayesian estimation, the elastic constants of specially orthotropic cylindrical composite shells with balanced symmetric lamination were characterized based on their natural frequencies obtained from free-free configuration modal testing. Estimation of the various elastic constants of each cylinder involved an iterative tuning of a mathematical model describing its modal response. Formulation of the model was accomplished with the Rayleigh-Ritz method in conjunction with characteristic beam functions. For a prescribed circumferential wave pattern of the vibration modes, a five-term series was sufficient to describe the deflection shapes. By carrying out sensitivity analysis, the natural frequencies of the cylindrical shells were found to have a high dependence on the circumferential and in-plane shear moduli rendering an accurate characterization for these moduli. On the contrary, the Poisson's ratios of the specimens cannot be accurately determined.