This thesis is devoted to the dynamic fracture of functionally graded materials. More particularly, it deals with the toughness of nuclear cladding at high burnup submitted to transient loading. The fracture is studied at local scale using cohesive zone model in a multibody approach. Cohesive zone models include frictional contact to take intoa ccount mixed mode fracture. Non smooth dynamics problems are treated within the Non-Smooth Contac Dynamics framework. A multiscale study is necessary because of the dimension of the clad. At microscopic scale, the effective properties of surfacic law, between each body, are obtained by periodic numerical homogenization. A two fields Finite Element formolution is so written. An extended formulation of the NSCD framework is obtained. The associated software allows to simulate, in finite deformation, from the crack initiation to post-fracture behevior in heterogeneous materials. At macroscopic scale, calculations of part of clad are made to determine the role of the mean hydrogen concentration and gradient of hydrogen parameters in the toughness of the clad under dynamic loading.