The most simple approach is the one with three-dimensional isotropic damage where we assume that the microdefects are statistically distributed in all spatial directions. The damage is then quantified by one scalar variable "d". Generally, this model is not verified experimentally because the damage studied is in anisotropic materials like composite materials.

The main objective of this paper is to study and assess the anisotropic damage coupled with anisotropic elasticity in brittle-brittle composites. We show that the conventional mechanics metrologies are not well adapted to conduct this kind of study in a single sample. However, for example in a ceramic-ceramic composite material an ultrasonic interferometer method allows us to assess the anisotropic damage and to follow its evolution under a tensile test. The constitutive and evolution laws used to model the damage phenomenon under uniaxial tensile test conditions are fully verified.