In this paper the 3-D Cartesian braiding process is described, and a finite element based method is proposed for determining the mechanical properties of this class of textile composites. In the investigation of the yarn structure of the preform a control volume approach is pursued whereby the paths of the yarns (fibers) entering and leaving a given volume of the preform, coincident with the movements of the yarn carriers on the braiding machine, are observed. A three dimensional representation (tiber architecture) of the braided composite, including the axial yarns, is given. The finite element based method proposed for modeling the braided composite treats the yarns and the matrix as distinct finite elmeents, with no smearing as is customary in lamination theory. the FE model os the 3-D braided composite is obtained by superposition of these finite element models and application of certain constraints. Estimates of the variation of the elastic constants of the 3-D braided composite are developed as a function of different percentages of axial yarns and "interior braiding angle" for a 50
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