Improvement in toughness of carbon/carbon composites using multiple matrixes

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. (C) 2011 Elsevier B.V. All rights reserved.