Investigation of Elastic Parameters of Three-Dimensional Full Five-Directional Braided Composite Materials

The aim of this paper is to investigate the material constants of three-dimensional full five-directional (3Df5d) braided composites. Based on the yarn deformation mode, the relation between material constants and braiding parameters is systematically deduced. The technological factor λ is proposed using the energy theory with consideration of the cross section and lateral deformation of axial yarns after solidification. Longitudinal moduli of all the unit cells are modified, and analytical solutions regarding λ are eventually obtained with volume average method. The results show that the elastic properties of this material are strongly designable and closely related to internal braiding angle and fiber volume fraction; the longitudinal modulus highly depends on λ which ranges from 1.3 to 2 according to technological level and it coincides well with the experimental results when λ takes 1.3; increased λ can guarantee better geometrical morphology of axial yarns and thus enhance the axial mechanical properties; the longitudinal modulus can still be improved by about 20%, relative to the test data, which seems unrelated to the braiding parameters. The developed methodology performs well in predicting the material constants of 3Df5d braided composites, which can be of certain significance for other textile materials.