The Study Of Creep Properties Of Three Dimensional Braiding Preform Reinforced Resin Composites

Three dimensional braiding preform reinforced resin composite is a new type of advanced composites and used in aircraft and space, transportation, construction, military project, medical treatment and physical education etc. 3-D braiding composites will subject to long-term tensile force during applied process, which is a long-time creep process. So creep property is an important guideline to characterize its mechanics performance. The research of three dimensional braiding preform reinforced resin composite's creep property was conducted systematically by this thesis with creep testing system, experimental analysis, theoretical analysis, and some new opinions and methods are proposed. The main contents of this thesis include:Investigating many documents about creep research closely about textile composites , which is a basement for creep studying of 3-D braiding composites.3-dimensional 5-directional braiding composites improve the axial mechanical properties of the composites by inserting the axial fibers. In the second section, the paper studied the microstructure of 3-dimensional 5-directional braiding preform and its reinforced composites. The unit model is established. Then the ralationship of the braiding parameters were deduced, and the fibre volume content was calculated. The predictions have shown a good agreement with the experiment results.The creep testing method was studied thoroughly in this paper. The whole creep testing system is developed by creep machine, extensometer, resistance strain gage, A/D translation board, computer and a set of software which can collect creep data automatically. Creep specimens (different braiding structure, surface braiding angle, fibre volume content and under different loads )were tested ,which is the basis of studying their creep behaviors. Then the experiment data were delt with correctly. The conclusions and the fit equations were got. 3-D braiding composite's life span is predicted by extrapolating its creep behavior based on the combination of testing data and theory formula.At present, the research on 3-D braiding composite's creep behavior were little, however, the influence of 3-D braiding composite's creep property on its applied procedure is large. So the work of this thesis will have significant meanings for the theoretical research and applications of 3-D braiding composites.