Mapping the failure envelope of a filled silicone elastomer to determine a failure criterion

Multiaxial stress states often develop in common structures, such as joints, corners, and thin-walled shells. Developing criteria that map the failure of materials under multiaxial stress states is thus essential to selecting materials during the design process. Here, failure refers to the catastrophic rupture that occurs in a material upon the development of a critical stress that defines its ultimate strength. While such analyses have long been applied to quantify the yielding behavior of stiff materials, such as metals and glassy polymers, limited measurements of the multiaxial strengths of soft rubbery polymer networks are available in the literature. Using biaxial deformations, this work characterizes the strengths of a commercially available filled silicone elastomer under multiple stress states and maps its failure envelope in planar principal stress space. The first quadrant of planar principal stress space is characterized by applying biaxial extension to cruciform samples. The second quadrant is then mapped by applying both tension and torsion to cylindrical samples. By combining these measurements, it is observed that the failure envelope for this commercially available filled silicone elastomer is consistent with a maximum principal stress failure criterion.