Microstructure quantitative analysis of multi-scale pores in C/SiC composites via micro-CT for revealing correlations with interlaminar shear properties

Abstract

Fiber reinforced Ceramic Matrix composites (CMCs) are widely used in aerospace fields due to their excellent properties. However, pores are inevitable during CMCs manufacturing, due to their anisotropy and fabrication complexity. Pore is a key factor that induces material microstructure inhomogeneity, thereby affecting mechanical properties and compromising component safety. The conventional indicator porosity cannot characterize detailed pore structure characteristics. To accurately evaluate effects of multi-scale pores on composites or components properties, a modified fractal dimension analysis strategy is proposed to quantify the microstructure characteristic parameters of pores such as porosity, pore size and distribution, etc, using micro-computed tomography images (Micro-CT) images. Moreover, the correlations between the modified box-counting dimension with multiple pore characteristics are investigated to accurately identify pore types of carbon fiber reinforced silicon carbide (C/SiC) composites. Combining short-beam shear test with quantitative pore analysis, this study develops a least squares regression model to reveal the correlation between the box-counting dimension and interlaminar shear properties in C/SiC composites. The results show that the box-counting dimension-based approach successfully quantifies and identifies among three pore types: isolated, locally connected, and large-area connected pores. Scale range of pores is from micrometers to millimeters. A strong linear fitting correlation exists between the modified box-counting dimension with shear properties of C/SiC composites, which reveals that the pores with large area connectivity can significantly degrade the properties. This work provides a strong data basis and an applicable method for mechanical properties evaluation and optimal design of fiber reinforced CMCs and other similar structural composites.

Keywords

• Carbon fiber reinforced silicon carbide composites
• Multi-scale pores
• Microstructure quantitative analysis
• Box-counting dimension
• Interlaminar shear properties