Contribution to Guided Waves Analysis at Low Frequency in Thin Absorbing Plates with Application to the Non Destructive Testing of Paper

The paper is a cellulose fiber base material and consequently it is heterogeneous at different scales. In addition, the paper exhibits two preferential axes of fiber orientation, from which it is easy to define the characteristics of an elementary bi-dimensional fiber network. A third axis, perpendicular to the first, corresponds to the stacking direction of individual networks. Following the example of composite layered media modeling, the paper presents three perpendicular planes of material symmetry. In other words, the paper is commonly assumed to be an orthotropic material [1]. The paper presents also various mechanical behaviors such as elasticity, viscoelasticity, non-linear elasticity. Furthermore the paper properties depend on both the temperature and the hygrometry [2]. At last, paper materials exist in the form of sheets; their thickness (100 µm on average) is very small beside their other dimensions.