NASA 4750 Manual

A SERVICE OF

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ANALYTICAL METHODS FOR TEXTILE COMPOSITES

8-6

Strength

Model:

None.

Data

Required:

Yarn and matrix elastic constants. Different yarns may have different properties.

Points describing yarn paths and cross-sections must be generated external to the

program.

Output:

6x6 average stiffness matrix, A, B, and D matrices (plate option), thermal

expansion coefficients, and yarn volume fractions. Finite-element nodal coordinates

and connectivity arrays are also given.

Experimental

Validation

:

None offered.

Comments:

- Combining isostrain and isostress can be physically justified in a composite.

However, the user should be aware that there is no way to tell if an upper or lower

bound is being obtained.

- Like µTex-10, this code computationally intensive. A solution for µTex-20

using a 20x20x20 mesh required about an hour on an HP 7000 workstation. The

authors report a quarter of this time using a different computer.

- Stress output is not available.

- Given that the effort to set up data files is identical for µTex-10 and µTex -20,

the advantages of µTex-20 are not obvious. It may be preferable to obtain an

upper bound solution from µTex-10, which is known to converge with increasing

mesh density, rather than to introduce the uncertainty of the selective averaging

method.