Material Redefinition

Modify a material definition using the HIN file.

In many analyses, you may wish to modify a material definition slightly to perform a sensitivity analysis. The sensitivity study would force you to modify either the static material properties or the dynamic data for the desired analyses. The dynamic material data can already be modified through the MATPFA entry in each analysis. To modify the static material data, you would typically have to recreate the material of interest with the different material parameters and save it to the Helius PFA materials database. Obviously this could become very cumbersome for a large sensitivity analysis as a new material would have to be saved to the database for each analysis, which is not desirable.

To accommodate a use case as described above, the HIN file allows you to overwrite certain material parameters for a specific material in the materials database using the keywords below.

For unidirectional materials:

*MATERIAL, ID=MIDH, FVF=NEWFVF, MOISTURE=AMBIENT/DRY/WET
pS11, nS11, pS22, nS22, S12, S23
*FIBER
E11, E22, v12, v23, G12, CTE11, CTE22
*MATRIX
E11, E22, v12, v23, G12, CTE11, CTE22

For woven materials:

*MATERIAL, ID=MIDH, FVF=NEWFVF, MOISTURE=AMBIENT/DRY/WET
pS11K, pS11U, nS11K, nS11U, S12K, S12U
*FIBER
E11, E22, v12, v23, G12, CTE11, CTE22
*MATRIX
E11, E22, v12, v23, G12, CTE11, CTE22

The *MATERIAL keyword has several optional parameters and multiple sub-lines to change constituent material properties. The parameter FVF is used to override the fiber volume fraction of the lamina. If this parameter is omitted, the fiber volume fraction contained in the material file will be used. The MOISTURE parameter is used to change the moisture content of the material and thus the material property set read from the material file. If this parameter is omitted, the default value of AMBIENT is assumed. The line beneath the *MATERIAL keyword contains the strengths of the lamina. For woven materials, you can specify both the ultimate (U) and knee (K) strengths of the lamina. If the line is omitted, the values from the materials database are used.

The sub-keywords *FIBER and *MATRIX are used to override the fiber and matrix material properties for the specified material. The corresponding data lines allow you to specify individual properties for each constituent. Note that transverse isotropy is always enforced for the elastic constants, lamina properties are generated after the material properties have been changed.

Consider an analysis using material IM7_8552 (MIDH = 9030, for example) in the Helius PFA materials database. The Autodesk Inventor Nastran material definition would appear as follows:

MATPFA, 1, 9030, 1, MCT, 0.01, 1.00E-02, INSTANT, OFF,
, AMBIENT, 0

Now consider the consequences if you wanted to change the fiber volume fraction of the material from 60% to 58%, the longitudinal tensile strength from 2500 MPa to 2000 MPa, the fiber longitudinal modulus from 245 GPa to 300 GPa, and the matrix Poisson ratio from 0.28 to 0.35. The corresponding *MATERIAL card in the HIN file would appear as follows:

*MATERIAL, ID=9030, FVF=0.58
2000.e6, , , , , 
*FIBER
300.e9, , , , , ,
*MATRIX
, , 0.35, 0.35, , ,

In this example, the MOISTURE parameter was not specified, and therefore Helius PFA will use the default moisture content of Ambient in the material file. Note, any material parameter that is to be defaulted to the value in the material file is specified as blank.

If none of a constituent's properties or the composite strengths were to be modified, the specific data line(s) could be removed. For example, if none of the fiber properties except the fiber volume fraction were to be changed, the *MATERIAL keyword would appear as

*MATERIAL, ID=MIDH, FVF=0.58
2000.e6, , , , , 
*MATRIX
, , 0.35, 0.35, , ,

Note: To redefine material properties for a material that is being mapped to another material with the *MAP keyword, you must use the ORIGINAL ID= parameter. For example:

*MAP, FROM=ID, TO=ID
9002, 9001
**
*MATERIAL, ORIGINAL ID=9002
*MATRIX
, , 0.35, 0.35, , ,

Otherwise, only the base material being used (9001) will have the properties modified. If you change any material properties of the base material using the *MATERIAL keyword, it will affect all materials mapped to that material.

Note: This functionality is not supported for woven materials.