Dislocation emission at fibers-II. Experiments and microstructure of thermal punching

A decoration technique is used to observe dislocations produced by thermal stresses between glass or alumina fibers and silver chloride, used as a model material for metal matrix composites. Fibers ends are found to punch prismatic loop rows, the length of which is compared with a model presented in Part I of this paper as well as another model based on a mismatching spheroid. The geometry of dislocations punched at fiber ends is discussed for the case where the fiber axis is not coaxial with the glide direction. Elongated loops are also observed to be punched radially by the fiber and their number is correlated to the thermal radial mismatch. A simple model is proposed for the nucleation of such loops, which are usually entangled in a plastic zone surrounding the fiber.