ANALYTICAL METHODS FOR TEXTILE COMPOSITES
8-8
Macroscopic stiffness is computed by orientation averaging (isostrain conditions).
Each yarn is discretized into slices. Volume averaging is effected by numerical
integration along yarn paths, using the local material properties and spatial
orientation. The code also gives laminated plate stiffness matrices (A, B, and D)
and can stack multiple layers using lamination theory. Nesting patterns are not
accounted for when layers are stacked.
Model:
TEXCAD has several nonlinear features that aid in estimating failure.
- The nonlinear shear response of the impregnated yarns and resin is represented by
a power-law relation.
- Bending of undulating yarns is modeled as the response of curved beams on
elastic foundations. Yarn splitting is also accounted for in this model.
- There is a stiffness reduction algorithm that is applied when local damage is
detected.
- First order effects of geometric nonlinearity due to yarn straightening or wrinkling
are included.
- Failure is based on the constituent stress obtained from an isostrain model. Failure
may also occur if the bending stresses in the models of beams on elastic
foundations reach a critical value.
Required:
Stiffness and strength for yarns and matrix. Geometric parameters depend on the
textile analyzed. They generally include yarn spacing, fiber volume fraction in yarn,
yarn filament count, filament diameter, overall fiber volume fraction, and braid
angle.
Output:
Three-dimensional stiffness matrix, plate stiffness elements, thermal expansion
coefficients, nonlinear stress-strain response (tabulated), failure sequence.
