Micro-structure Design And Calculation Of Carbon-Carbon Braided Composite Material

Because of high Specific Strength and Specific Stiffness, excellent high temperature properties, outstanding resistance to shock damage and the ability insensitive to cracking and damage expanding, carbon-carbon braided composites are widely used in aerospace area, as same time, it aroused material researchers'general interest. However, the research methods which basis on test is cost much but not efficient and macro test is lack of characterization to micro performance, so these methods can not explain the nature of material performance. As a result, this article analyzes carbon-carbon braided composite's material properties from the microscopic point of view while taking numerical technique as guide, expecting to provide theoretical support and data reference to composite material structure optimization and properties characterization. The main content of this paper is as follow:First, evaluate the defect affect on mechanical properties of carbon-carbon braided composite on the base of representative volume element (RVE) model, while taking the micro-scale defects in materials as main object of study, and compare harmful level among different defects. Then, mix various defects together and simulate actual conditions that may exist in production process. Predict the change of mechanical properties under defects so as to research the affect to the whole material.Second, carbon-carbon braided composites generally have heterogeneous characteristics. For the purpose of simulating this characteristic, the original RVE model is improved by implanting anisotropic interface and matrix in it. Analyze the effect of heterogeneity to the mechanical properties of the model, and then add defects into the model, calculate changes in mechanical properties caused by defects, obtain 'the defects effect theory.Last, make Micro-structural optimization to the model. Extract fiber and surrounding interface from representative volume element (RVE) of carbon-carbon braided composite as the object of study, called carbon fiber and interface (CFI) model. Impose the temperature field of RVE where the fiber is extracted from to the CFI model under local coordinates. Using finite element method to do sequential thermal-mechanical coupling calculation, then get the stress distribution around nano-groove under local coordinates, use the result to evaluate engage force between fiber and interface and analyze the nano-groove influence on the binding properties. assess the feasibility of the Micro-structural optimization.