A Three Dimensional Finite Element Structural Model of Textile Composites

There is a lack of analytical methods and results to predict the bulk elastic properties in textile composites. The difficulty in the development of an analytical method lies in the large number of internal geometric variables which impact the final bulk stiffnesses. Some of them include: fabric braid angles, Young’s modulii of the constituent laminate and the matrix, and the algorithm for the braid or weave orientations. This paper describes an analytical method and model for predicting the bulk elastic properties for 3-D, 4 step braided composites. This method is supported by limited experimental data from other researchers. An FEM analyses has been chosen as the basis for the structural model. The element chosen was a 3-D, 20 node isoparametric solid ANSYS element. A pre-processor generates the finite element model information required for the braid in ANSYS format. Nodal coordinates, element connectivities, fiber tow orientations, and the appropriate position and orientation of the fibers in the track and column braiding algorithm are all accounted for. Results are reported for the 3 x 14 four-step (track & column) braid analyzed as structural cells of 4 by 5 by 16 in size. The stiffnesses agree well with limited experimental data.