Three-dimensional sintering morphology simulation of silica fibrous insulator and its quantitative description

Silica fibrous insulator possessing excellent thermal properties is widely used in the aerospace engineering field. A finite element model is developed for simulating the solid-state sintering process in the preparation process of the fibrous insulator. The model is capable of simulating initial surfaces with complex geometric features. The model is validated by using the classic double-sphere diffusion model and comparing the simulation results with the experimental results in the reference. Results suggest sintered morphology is strongly controlled by the highest holding temperature and has little relationship with the heating rate. The detailed simulation parameters for sintering fibrous silica are determined by the experiment of sintering parallel fibers. Comparison between the simulation results of planar simplification model, double-sphere model, and double-cylinder model reveals the significance of neighborhood diffusion on the sintering of parallel fibers. We found the morphological geometric feature of the sintered fibrous body is consistent and accordingly the Feature Neck Ratio (FNR) is defined to quantitatively describe the degree of sintering and the morphology feature of the sintered fibers. From the perspective of the sintering morphology, when FNR reaches about 0.7–1 no matter how the sintering route is, the fibers are considered to be fully sintered together.