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Multi-scale Homogenization modeling of C/SiC composites
coPI: Anthony M. Waas
Collaborator: Veera Sundararaghavan (PI)
Particpant:Sangmin Lee


My research project is multi-scale homogenization of moving interface problems with flux and field Jumps. In this project, specifically, carbon reinforced silicon carbide(C/SiC) composites that are subject to large thermal stresses and high temperature oxidizing environments have been considered. These conditions progressively degrade the C-fibers and the SiC matrix which eventually leads to failure of the component well short of its expected life. In order to evaluate these phenomena, a computational homogenization method has been employed. Computational homogenization is a multi-scale analysis approach in which computations are performed at two different length-scales. The macro-scale is associated with the component being modeled (10e-3 to 10e+1 m) and the meso-scale is characterized by the underlying composite microstructure (10e-6 to 10e-3 m).

The multi-scale modeling of C/SiC composites is mainly focused on the problem of oxidation of carbon fiber and evaluating mechanical properties by linking macro, meso, and micro as shown in Fig 1. Firstly, in order to evaluate the C/SiC composites at a high temperature, the meso scale in which tows and matrix mixture is modeled has been employed. Secondly, from tow, to see the oxidation phenomena, the microscopic models which are including carbon fiber’s evolution are considered. In this micro model, since we need to know crack opening and its growth for the diffusion of oxygen and carbon dioxide, further small scale, molecular structures will be modeled to simulate the plasticity deformation. Finally, based on the microstructure evolution, in meso- and macrostructure, mechanical properties such as strength and stiffness will be computed as a function of thermo-chemo-mechanical loading of the composite by the consistent averaging scheme.

Fig. 1. C/SiC composites in extreme thermo-chemo-mechanical loading conditions are subject to a variety of degradation mechanisms. Modeling of macro-scale degradation should involve physical models at multiple length scales. In this paper, we focus on micro-scale degradation modeling using finite element analysis.

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