Stress at a distance fracture criteria and crack self-blunting in rubber

• Fracture from blunt cracks.
• Criteria of fracture, GcGc, σcσc and critical distance c¯.
• Self-blunting of sharp cracks.
• Cutting of stretched rubber sheet.

The elastic analysis for a blunt crack is used together with the fracture criteria of a critical energy release rate and a cohesive stress. The notion of this stress occurring at some distance from crack tip is explored and bounds for possible fracture behaviour are derived. The upper bound seems to model fracture in ceramics and polymers and is very similar in form to cohesive zone results for a linear traction curve. This small strain elastic solution is extended to include self-blunting from the deformation. It is shown that it gives a sensible description of the behaviour of rubber and it is used to model the cutting of a stretched sheet.