Recherche de defauts de collage dans les structures sandwich

One of the major defects that can be found on composite sandwich structures is poor bonding of the core on the exterior skins, particularly with the technique of bonding under vacuum. Therefore, we have looked at all the possible means of detecting these bonding defects, with two objectives: to be able to control integrally a piece of large dimensions, and to be able to control the piece in the course of manufacturing, that is to say after the bonding on the first skin. All of the non-destructive test methods now known have therefore been tested, and in particularly infrared thermography, ultrasonic control, and acoustic methods. This study, carried out in collaboration with the CETIM, the STCAN, Aerospatiale and other laboratories and companies without non-destructive controls, has made it possible to give an exhaustive state-of-art on the subject. Today, several methods seem promising. Among them one, developed by the Rolls Royce Mat Eval company, seems easily adaptable right now to the search for bonding defects in sandwich structures.