Improvement in toughness of carbon/carbon composites using multiple matrixes

[Display omitted] ► Carbon/carbon (C/C) composites. ► C/C composites with multiple matrixes present mixed microstructures. ► C/C composites with multiple matrixes exhibit super mechanical properties. ► Cracks may spread along multiple paths such as interface of different constituents. ► Multi-path for extension of crack improves mechanical properties of C/C composites. Carbon/carbon (C/C) composites with multiple matrixes were fabricated by impregnation/carbonization and chemical vapor infiltration (CVI) using 2-dimensional (2D) carbon felts preform. In order to study the effects of microstructure on mechanical properties, C/C composites with single matrix of pitch based carbon were prepared for comparison. The mechanical properties were tested on CMT5304-30KN universal testing machine. Polarization microscope and scanning electron microscope were used to investigate the microstructures and fracture surface of C/C composites. It was resulted that the flexural strength of C/C composites with multiple matrixes was improved by 83% compared with that of C/C composites with single matrix. Meanwhile, better toughness and pseudo-plastic fracture behaviors were also obtained with multiple matrixes. Multi-layer interfaces between different constituents were formed in the composites which supplied variety of extension paths for cracks. This microstructure character improved the mechanical properties of C/C composites, especially the toughness, as more energy could be dissipated during cracks spread along multiple paths, such as the interface of different components or among the matrixes.