Three-dimensional Multi-compressive Properties Of Textile Composite

From the 80's of twenty century, three-dimensional braiding composites, for its excellent mechanical properties, have been got more and more extensive researches and applications. Compression properties are an important guideline to characterize its mechanical performance. The compression behavior of three-dimensional braided composites was studied systematically with the experimental method, and some new opinions and methods were proposed. In addition, the microstructure of three-dimensional six-directional braided performs was studied, and its unit cells were established.Compartmentalizing the unit cell reasonably is very important for the microstructure analysis of three-dimensional braided preforms. The real structure and the yarn shape in the preform were observed by experiment and the assumption was bring forward of the yarns' cross-section in the three-dimensional six-directional braided preform. In this paper, a volume-control method was adopted. Based on the experimental observation, the yarn skeletal structure was presented and the initial cell and the surface cell were identified in the preform. And the relationships between braiding parameters were deduced. Fiber volume fraction was predicted, and a good agreement with the experiment results has been shown.The compression testing method was studied in detail. Referring to the correlative test methods and standards of fiber-reinforced composites, the testing device was developed. All specimens with different braiding structure, braiding angle and yarn diameter were braided and consolidated in our lab. The experiment was done on the SHIMADZU AG-250KNE mechanical test machine. The experimental data were dealt with correctly, and the relationships between compression properties and the braiding parameters have been investigated for three-dimensional five-directional and six-directional braiding composites. Finally, the compression failure mechanism was summarized and some valuable conclusions were received.At present, the systematical research on the compression behavior of three-dimensional braided composite was little. So the work of this paper will have significant meanings for the theoretical research and applications of three- dimensional braiding composites.