A MICROMECHANICAL MODEL FOR TEXTILE COMPOSITE PLATES

A novel finite element based micromechanical method is developed for c omputing the plate stiffness coefficients (A, B, D matrices.) and coef ficients of thermal expansion (alpha's and beta's) of a textile compos ite modeled as a homogeneous plate. Periodic boundary conditions for t he plate model, which are different from those for the continuum model , have been derived. The micromechanics methods for computing the coef ficients of thermal expansion are readily extended to compute the ther mal residual stresses due to curing. The methods are first verified by applying to several examples for which solutions are known, and then applied to the case of woven composites. The plate stiffness coefficie nts computed from direct micromechanics are compared with those derive d from the homogenized elastic constants in conjunction with the class ical plate theory. It is found that the plate stiffness coefficients o f textile composites, especially the B and D matrices, cannot be predi cted from the homogenized elastic constants and the plate thickness.