Abstract One route for producing fiber-reinforced ceramic-matrix composites entails repeated impregnation and pyrolysis of a preceramic polymer in a fiber preform. The process relies crucially on the development of networks of contiguous cracks during pyrolysis, thereby allowing further impregnation to attain nearly-full densification. The present study employs in-situ x-ray computed tomography (XCT) to reveal in three dimensions the evolution of matrix structure during pyrolysis of a SiC-based preceramic polymer to 1200 °C. Observations are used to guide the development of a taxonomy of crack geometries and crack structures and to identify the temporal sequence of their formation. A quantitative analysis is employed to characterize effects of local microstructural dimensions on the conditions required to form cracks of various types. Complementary measurements of gas evolution and mass loss of the preceramic polymer during pyrolysis as well as changes in mass density and Young's modulus provide context for the physical changes revealed by XCT. The findings provide a foundation for future development of physics-based models to guide composite fabrication processes.

中文翻译：

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聚合物到陶瓷转化过程中复合材料微观结构的原位 3D 可视化

摘要 生产纤维增强陶瓷基复合材料的一种方法是在纤维预制件中反复浸渍和热解陶瓷前驱体聚合物。该过程主要依赖于热解过程中连续裂缝网络的发展，从而允许进一步浸渍以达到几乎完全致密化。本研究采用原位 X 射线计算机断层扫描 (XCT) 从三个维度揭示 SiC 基陶瓷预聚物热解至 1200 °C 期间基体结构的演变。观测用于指导裂缝几何形状和裂缝结构分类的发展，并确定其形成的时间顺序。采用定量分析来表征局部微观结构尺寸对形成各种类型裂纹所需条件的影响。热解过程中陶瓷前体聚合物的气体逸出和质量损失以及质量密度和杨氏模量的变化的补充测量为 XCT 揭示的物理变化提供了背景。这些发现为未来开发基于物理的模型以指导复合材料制造过程奠定了基础。