AN EXPERIMENTAL-STUDY OF FAILURE IN CIRCUMFERENTIALLY NOTCHED ELASTOMER CYLINDERS

Cylindrical dumbbell specimens containing deep circumferential cracks were loaded in tension until failure to investigate the fracture proce ss in thick carbon black filled elastomers. Failure occurred at large deformations and was characterized by material tearing and small amoun ts of slow stable crack extension until rupture. The tearing process i tself consisted of two distinct phenomena, delamination and crack exte nsion. Upon load application, parabolic and asymmetric blunting of the crack tip was observed followed by a visible separation of the fabric ated crack surfaces into upper and lower crack surfaces connected by a n inner core of elastomer material. Localized material failure, identi fied as delamination, occurred along the outer surface of this inner c ore between the fabricated crack surfaces. Crack extension in the load direction was found above and below the fabricated crack surfaces. Bo th qualitative and quantitative aspects of failure were studied. Load and crack mouth opening displacement (CMOD) histories were examined, a nd the stretch ratio and tearing energy at rupture were measured. Fina lly, a model describing the tearing process was discussed.