A UNIT-CELL MODEL OF TEXTILE COMPOSITE BEAMS FOR PREDICTING STIFFNESSPROPERTIES

Flexural stiffness properties of a textile composite beam are obtained from a finite-element model of the unit cell. Three linearly independ ent deformations, namely, pure extension, pure bending and pure shear, are applied to the unit cell. The top and bottom surfaces of the beam are assumed to be traction free. Periodic boundary conditions on the lateral boundaries of the unit cell are enforced by multi-point constr aint elements. From the forces acting on the unit cell, the flexural s tiffness coefficients of the composite beam are obtained. The difficul ties in determining the transverse shear stiffness are discussed, and a modified approach is presented. The methods are first verified by ap plying them to isotropic and bimaterial beams for which the results ar e known, and then illustrated for a simple plain-weave textile composi te.