Craze topography by Scanning force microscopy: Micro-necking operative during crazing in polymer glasses

The phenomenon of crazing, i.e. the formation of narrow fibrillated regions surrounded by non-deformed material in stretched polymer glasses, is important because it is responsible for the brittle failures in glassy polymers. The crazes have been extensively studied in the past, notably by the transmission electron microscopy, and it was commonly accepted that the formation of the craze fibrils is dominated by a surface drawing mechanism. Namely, the fibrillation takes place and is boundary. Once the fibrils are drawn from the narrow strip into the craze, the fibrils thereafter maintain their geometry, spacing, and the state of deformation. The authors have recently used scanning force microscopy (SFM) to study the topography of crazes. The results, however, showed evidence of a different mechanism operative during crazing.