On the initiation and growth of kink bands in fiber composites: Part I. experiments

The initiation and growth of a kink band in a uniaxial composite is investigated experimentally. Experiments on unidirectional plates of AS4/PEEK were conducted using a custom biaxial testing device. A relatively stable post-failure response which occurs for displacement controlled shearing under a compressive preload is exploited to observe quasistatic kink band growth. The band initiates from a stress concentration on one of the free edges and grows across the specimen with a constant inclination of about 12 degrees. Detailed in situ measurements show that the fiber rotation and band width at a point increase as the band goes past it. After traversing the specimen, the band propagates (broadens) with constant fiber rotation. The observed kink band characteristics were similar to those of kink bands which grew dynamically in the same composite tested under pure compression. A difference is that the ends of the bands formed under combined compression and shear are highly bent but not broken. (C) 2001 Elsevier Science Ltd. All rights reserved.