Appendix A.4 - Failure Theory (FT)

Helius PFA contains several common failure criteria. These failure criteria control only the initiation of damage. The progression of failure is handled the same regardless of the failure criterion used. Refer to the Theory Manual for a detailed description of each criterion.

For unidirectional composites, the available failure criteria are listed below with the appropriate value for the FT field:

• MCT - Multicontinuum Theory (default)
• STRESS - Max Stress
• STRAIN - Max Strain
• HILL - Tsai-Hill
• TSAI - Tsai-Wu
• CHRIS - Christensen
• HASH - Hashin
• PUCK - Puck
• LaRC02 - LaRC02
• USER - User-defined

For woven composites, the available failure criteria are:

• MCT - Multicontinuum Theory (default)
• STRESS - Max Stress
• STRAIN - Max Strain
• USER - User-defined

The Tsai-Wu and Hashin criteria require the specification of auxiliary criterion parameters. Tsai-Wu requires two auxiliary parameters and Hashin requires one parameter. These parameters are specified by the F/ALPHA and SBIAX fields.

In addition to the failure criteria listed above, Helius PFA also provides a simple interface if you wish to create your own failure criterion subroutines. This functionality is covered in detail in the Installation and Operations Guide.