One considers a structural element constituted of a complex material modeled by an elastic isotropic homogenous medium at the macroscopic scale. An uncertain model is then constructed and is constituted of a random field modeling the Young modulus. This random field is represented by a polynomial Gaussian chaos decomposition. A method has recently been proposed to identify such a chaos development in the context of elastostatic. In this lecture, an extension to the elastodynamics case is presented. The chaos rerpresentation is identified by using an experimental database constituted of vibrational tests related to specimens. The identification problem consist in identifying the coefficients of the chaos representation by using the experimental database related to the dynamical repsonse of the specimen.