Endommagement des matériaux composites : mécanismes et mise en évidence^*

The damaging of composite materials: mechanisms and detection

Professeur à l’U.T.C.

Abstract

Although quasi-elastic, the rupture of composites is preceded by microscopic damage which advances slowly and can be anticipated. The first damages that can be observed with an optical microscope are microcracks that appear in the matrix, at about one-third of the load at fracture. Fibers damaging does not occur until the moment of fracture. Between these two stages of damage is a third one : the fissuring of the fiber/matrix interface.

All these damages are internal, even in the case of fatigue where the surface has practically no role to play, contrary to what is observed for metals. The criteria for the damage and fracture of composites must necessarily take into account their three-dimensional nature. On a phenomenological level, the study of this damage relies on such classical methods of observation as microscopy, but also on specific methods such as radiography, tomography or holography allowing better three-dimensional observations.

In this text will be examined the different types of damage, the fracture in presence of a notch, the models and the methods of observation of composite materials.