Modelling unilateral damage effect in strongly anisotropic materials by the introduction of the loading mode in damage mechanics

Damage weakens the mechanical characteristics of materials[ But this weakening can disappear if the cracks close again] this is called the unilateral e}ect of damage[ We propose a model of this phenomenon using damage mechanics in the case of a di}use network of identical microcracks[ The microcracks| state is de_ned with two internal state variables[ These two variables are control parameters of the geometry of the microcracks[ They also de_ne the loading mode in damage mechanics as in fracture mechanics[ In order to limit the anisotropy induced by the microcracks\ hence by the loading\ we suppose that the geometry of damage spreads into preferential directions[ Therefore\ this model is essentially applied to materials with a strong anisotropy where the defects follow the constituents of the material[ An application is given for composite laminates