Abstract:

In order to analyze the tensile property and failure mechanism of 3-D braided composites, three-dimensional five-directional (3D5d) and three-dimensional six-directional(3D6d) hybrid braided composites with carbon fibers and aramid fibers as axial and braiding yarns were designed and manufactured. A digital Image correlation (DIC) technique was used to record the surface full-field strain distribution of samples during tensile loading. At the same time, the Poisson’s ratios was also obtained by DIC. The test results show that Poisson’s ratio is mainly influenced by braided architecture. For the same braided architecture, the carbon-aramid  hybrid 3-D braided composites with carbon fiber as axial yarn maintain the tensile strength and modulus of carbon 3-D braided composites, while the ultimate tensile strain is higher than that of carbon -3D braided composites. the carbon-aramid hybrid 3-D braided composites with aramid fiber as axial yarn significantly improve the ultimate tensile strain of the composites, but seriousily losed the tensile strength and modulus of the composites. For the same hybrid braided structure, the tensile strength and modulus of 3D5d were higher than those of 3D6d. The ultimate tensile strain of 3D5d and 3D6d show few differences. The high strain regions of hybrid braided composites (axial yarns are aramid and carbon fibers, respectively) are appwoximately lattice and wave line distribution, respectively. The high strain regions of 3D5d and 3D6d are distributed uniformly and transversely, respectively.

Key words: 3-D braiding, hybrid braided composite, tensile property, Poisson's ratio