LAW25 (Tsai-WU and CRASURV)
LAW25 is the most commonly used composite material in Radioss. It can be used with shell and solid elements. The two formulations available in LAW25 are the Tsai-Wu and CRASURV formulations.
Elastic Phase
In the elastic phase, Young's modulus (3 parameters), shear modulus (3 parameters) and one parameter for Poisson ratio are required to describe the orthotropic material.
Tsai-Wu Yield Criteria for Iform=0 and =1
- Iform=0: Tsai-Wu
- Iform=1: CRASURV
- Tensile/compression tests
Longitudinal tensile/compression tests (in direction 1 which is fiber direction):
- Iform = 0: Tsai-Wu
- Iform = 1: CRASURV
- Here,
-
In tension:
In compression:
Here
Transverse tensile/compression tests (in direction 2)
- Iform = 0: Tsai-Wu
- Iform = 1: CRASURV
- Here,
-
In tension:
In compression:
Here
- Shear tests
Shear in plane 1-2
- Iform = 0: Tsai-Wu
- Iform = 1: CRASURV
- and can result from the sample tests:
-
- Here,
- Interaction coefficients
- Iform = 0: Tsai-Wu
- Iform = 1: CRASURV
- The default reduction factor, , is typically used.
- Here,
- Iform = 0: Tsai-Wu
- Iform = 1: CRASURV
- With
- Here
- Material in elastic phase, if
- Material in nonlinear phase, if
-
- The yield stress limit is in range of 1 and
- Material in elastic phase, if
In LAW25 (Tsai-Wu and CRASURV) damage is a function of the total strain and the maximum damage factor.
If the total strain or out of plane strain , the material is softened using the following method:
Where, di is the damage factor and is defined as:
- If the total strain is between , the material begins to soften, but this damage is reversible. Once , the damage is irreversible and if , then stress in material is reduced to 0.
- Damage could be in elastic phase or in plastic phase. It depends on which phase and are defined in.
- Element deletion is controlled by Ioff. Select a different Ioff option to control the criteria of element deletion. For additional information, refer to Ioff in LAW25 in the Reference Guide.