View details of each user-material constant for composite materials.
A set of user material constants are provided in the data line that immediately follows the *USER MATERIAL keyword statement. The Helius PFA User-Defined Material Subroutine uses these constants to determine the precise form of multiscale constitutive relations that should be used for the composite material. For any type of composite material, the number of user material constants must be between 3 and 18. The table below provides a short description of the feature controlled by each user material constant along with the allowable range of values for each constant.
User Material Constants for Composite Materials
| UMC | Constitutive Issue Controlled by the User Material Constant | Allowable Values |
|---|---|---|
| 1 | System of Units | 1, 2, 3, 4, 5 |
| 2 | Principal Material Coordinate System |
Unidirectional → 1, 2 Woven → 1, 2, 3 |
| 3 | Progressive Failure Analysis |
Uni → 0 (off), 1 (on) Woven → 0 (off), 1 or 2 (on) |
| 4 | Pre-Failure Nonlinearity |
Uni → 0 (off), 1 (on) Woven → 0 (off), 1 (on) |
| 5 | Damage Evolution Method |
0 (Instantaneous) 2 (Energy-Based - uni only) |
| 6 | Hydrostatic Strengthening | 0 (off), 1 (on - uni only) |
| 7 | Temperature |
-1 (activate temperature dependence) value ≥ 0.0 (temperature corresponding to environment in mdata file) |
| 8 | Failure Criterion |
Uni → -1, 0, 1, 2, 3, 4, 5, 6, 7, 8 Woven → -1, 0, 1, 2 |
| 9 | Auxiliary Criterion Parameter | -1.0 ≤ value ≤ 1.0 |
| 10 | Auxiliary Criterion Parameter | Must be > 0 |
| 11 | Average Element Thickness / Degradation Time Period | Must be > 0 / Must be ≥ 0 |
| 12 | Matrix Post Failure Stiffness / Matrix Degradation Energy | 0 < value ≤ 1 / Must be > 0 |
| 13 | Fiber Post Failure Stiffness | 0 < value ≤ 1 |
| 14 | Fiber Degradation Energy | Must be > 0 |
| 15 | Unused | Blank |
| 16 | Moisture |
Moisture flag corresponding to environment in mdata file: 0 (Ambient), 1 (Dry), 2 (Wet) |
| 17 | Matrix Strain Rate Strengthening Parameter | Must be ≥ 0 |
| 18 | Fiber Strain Rate Strengthening Parameter | Must be ≥ 0 |
The remainder of Appendix A discusses each material constant in detail, including the impact of the constant on the multiscale constitutive relations used to represent the composite material.