Quasi-plastic deformation mechanism and off-line secondary molding of four-step three-dimensional braided preform

The present curved-surface preform made by the process copying the mandrel is easy to appear quasi-plastic deformation. And this process with low-efficiency, high-cost is difficult to batch production. In this study, a tubular preform is obtained by the process of off-line secondary molding based on the plate preform. The deformation mechanism of the plate preform under different load conditions is analyzed. Establishing mathematical model based on the deformation of microstructure unit, the geometric dimensions and fiber volume fraction of the deformed preform are forecasted. Theoretical results show that the size of unit can govern the stability of preform in molding, the deformation of preform can increase the fiber volume fraction effectively when the units of plate three-dimensional braided material are cubic. The tubular preform made by the technology of molding the pre-designed plate preform which can be braided quickly has a more stable geometrical structure and better performance. This technology avoid the complex braiding process and equipment of the tubular preform, which is expect to product the tubular preform in batches effectively.