LIU Shijian ^{1, 2}, QIU Haipeng ^{1, 2}, LIU Shanhua ^{1, 2}, CHEN Mingwei ^{1, 2}, XIE Weijie ^{1, 2},ZHANG Bingyu ^{1, 2}, MA Xin ^{1, 2}, LUO Wendong ^{1, 2}

(1. AVIC Manufacturing Technology Institute, Beijing 100024, China; 2. AVIC Composite Corporation Ltd., Beijing 101300, China)

Abstract:  Although 2D SiC/SiC composites have the advantages of low textile processing cost and excellent in-plane mechanical properties, their poor interlaminar mechanical properties are the main factors limiting their practical applications. Based on automatic CNC sewing system and lock stitch method, SiC fiber preform was sewed by using SiC fibers with two methods to sew the SiC fibers, while sewing density was maintained to be same. The sewing 2D SiC fiber preform with PyC interface was densified through polymer infiltration and pyrolysis (PIP). Microstructure of the 2D SiC/SiC composites was characterized by using micro-CT and scanning electron microscope (SEM). Interlaminar mechanical properties at room temperature were also studied. It was observed that there was no difference in porosity and density between the two groups of 2D SiC/SiC composites. However, as compared with the 2D SiC/SiC composites in which the SiC sewing fiber was introduced as upper thread, those with the SiC sewing fiber to introduced as bobbin thread exhibited enhanced bending strength and interlaminar shear strength, by 12.4% and 20.0%, respectively. It is proved that the SiC sewing fiber to be introduced as bobbin thread is more effective in enhancing mechanical properties of the composites.

Key words:  SiC/SiC Composites; 2D; preform; sewing; automation