Multiaxial Characterization of Soft Polymers to Characterize a Failure Criterion

Characterization of the multiaxial mechanical behavior of soft solids is vital to understanding their behavior in common design structures such as joints, corners, and thin-walled shells where complex stress states develop upon loading. Despite this, most measurements performed on soft solids only subject the material to uniaxial loadings. Performing such measurements fails to thoroughly characterize aspects of the mechanical response, such as the large strain constitutive behavior and failure point, which are sensitive to the applied stress state. In this work, we investigate multiaxial failure by applying biaxial tension and combined tension/torsion on a common silicone elastomer. Biaxial tension is carried out with a recently developed cruciform design to characterize the failure envelope in the first quadrant of principal stress space. Further, combined tension and torsion are applied to cylinders to quantify failure in the second quadrant of principal stress space. These two techniques map the failure envelope for a common silicone elastomer and suggest a straightforward failure criterion. Applying such methods to soft yielding polymer networks is of great interest in the future.