NASA 4750 Manual

A SERVICE OF

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ANALYTICAL METHODS FOR TEXTILE COMPOSITES

8-18

Strength

Model:

None.

Data

Required:

Fraction of all fibers lying in stuffers, fillers, and weavers. Total fiber volume

fraction. Second moment of normal distribution of misalignment angles, yields of

stuffers and fillers, number of ends and picks, thickness of plate.

Output:

Tow elastic constants computed by micromechanical model. Three-dimensional

stiffness matrix for homogenized plate. Plate bending stiffness.

Experimental

Validation

:

Large data base of measured elastic constants for several weaves is given in the

references.

Comments:

WEAVE offers several novel features.

- WEAVE incorporates micromechanical models for tows. The elastic constants of

an impregnated tow are not generally available from experiments. The user must

predict values to use any of the codes. It is convenient to have the prediction tool

built-in.

- WEAVE (and MLM for braids - see third listed reference) incorporates a simple

rule (Eq. (3.1) of this handbook) for reducing the stiffness of tows to account for

stochastic waviness integration of the yarn stiffness over the specified distribution

of angles. The distribution may be obtained by analyzing micrographs or assigned

typical values in a sensitivity study.