Cutting as a Tool for Investigating Crack-Blunting-Involved Soft Fracture

During tearing of soft elastomers, large deformation occurs due to crack-blunting. The incorporated material nonlinearity alters the fracture response, resulting in a measured fracture energy value higher than the prediction from network binding energy [Lake and Thomas, 1967]. To understand the dependence of fracture energy on the nonlinear constitutive response, we control the crack tip geometry via cutting. A Y-shaped cutting geometry, inspired by Lake and Yeoh (1978), uses two separated “legs” to form a cutting notch that minimizes contact friction. A blade aligned with the notch imposes its radius during cutting. We find that cutting fracture energy increases nonlinearly with large blade radii. The radius sensitivity reflects the strain-stiffening constitutive response governing crack-blunting during tearing. However, as the blade radius decreases, the effect of nonlinearity is minimized and the cutting energy plateaus to a constant that appears to scale with elastic modulus. We evaluate the potential of cutting as a method for characterizing “intrinsic” fracture energy and provide insight into the microstructural origin of the plateauing transition using cutting tests from idealized, end-linked polydimethylsiloxane (PDMS) networks.