Helius PFA provides eight different failure criteria that can be used as alternatives to the default MCT constituent-based failure criteria.
These alternative failure criteria include the Max Strain, Max Stress, Tsai-Wu, Tsai-Hill, Hashin, Christensen, Puck, and LaRC02 criteria. It should be emphasized that each of the alternative failure criteria are simply used to identify the initiation of failure at individual integration points in the model. Once failure initiation occurs at an integration point, the default instantaneous degradation method is used for stiffness degradation. You may also request the use of the energy-based degradation method to control stiffness degradation after failure initiation. For those alternative failure criteria that distinguish between matrix constituent failure and fiber constituent failure (e.g., Hashin, Christensen, Puck, LaRC02), the stiffness degradation process is exactly the same as used for the MCT constitutive-based failure criteria. For those failure criteria that do not distinguish between matrix and fiber failure (e.g., Max Strain, Max Stress, Tsai-Hill, Tsai-Wu), the failure initiation condition is assumed to indicate the simultaneous initiation of both matrix and fiber failure. The remainder of this section describes each of the eight alternative failure criteria.