A CONSTITUTIVE RELATION FOR MICROCRACKED MATERIALS INCLUDING THE EFFECTS OF MICROCRACK OPENING CLOSING

In the general framework of the thermodynamics of continuous media (TC M) an clastic damageable model with a microcrack opening-closing thres hold is proposed to describe the nonlinear constitutive behavior of ce ramic-matrix composite. The assumptions currently made (based on physi cal considerations) are in fact a direct consequence of the implementa tion of TCM for these materials that have an internal constraint. When the applied stress is lower than the threshold stress the microcracks are inactive and the material has the behavior of the virgin one. But as soon as the stress level exceeds the threshold, the microcracks ar e active and the material has an elastic damaged behavior.