Appendix A.8 - User Material Constant #8: Failure Criterion Flag

Helius PFA contains several common failure criteria in addition to MCT. These failure criteria control the initiation of damage only; 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 user material constant 8:

• User (see below) - UMC8 = -1
• MCT (default) - UMC8 = 0
• Max Stress - UMC8 = 1
• Max Strain - UMC8 = 2
• Tsai-Hill - UMC8 = 3
• Tsai-Wu - UMC8 = 4
• Christensen - UMC8 = 5
• Hashin - UMC8 = 6
• Puck - UMC8 = 7
• LaRC02 - UMC8 = 8

For woven composites, the available failure criteria are:

• User (see below) - UMC8 = -1
• MCT (default) - UMC8 = 0
• Max Stress - UMC8 = 1
• Max Strain - UMC8 = 2

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 user material constants 9 and 10.

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.