Improvement of Bending Strength and Fracture Toughness of C/C Composite by Adding Carbon Particles with 3-Dimensional Web-Like Structures
Kiyotaka OBUNAI, Kazuya OKUBO and Toru FUJII
Abstract:This paper proposes an effective technique to improve bending strength and fracture toughness of C/C composite by adding carbonized Micro Fibrillated Cellulose (CMFC). In this study, conventional CFRP was carbonized at 1,700C with inert atmosphere to fabricate the C/C composites in which char matrix was made from phenolic resin. In order to fabricate the carbon particles with 3-dimensional web-like structures, the absorbed water of market available MFC was eliminated by freeze-drying technique, then MFC was carbonized at 800C with inert atmosphere. The improvement in the bending strength was appeared at the condition of 1.0 wt% of addition, while the excessive addition of CMFC was not effective to improve the bending strength. The morphology evaluation of fracture surface was revealed that the fiber braking was observed at the condition of 1.0 wt% of addition, while debonding was appeared on that of unmodified, 3.0 and 5.0 wt% of CMFC addition. The interfacial shear strength and fracture toughness were also improved when matrix was modified with appropriate contents of CMFC. The effect of CMFC addition on bending strength and fracture toughness of carbon matrix was also investigated. The local fracture toughness evaluated by IF(Indentation Fracture) test was increased with increase of CMFC contents. However, the bending strength of carbon matrix was increased when 1.0 wt% of CMFC addition, while the excessive addition of CMFC was not effective to improve the bending strength of carbon matrix. The agglomeration of CMFC was appeared due to the increment of viscosity of carbon precursor, when the excessive content of CMFC was added. Key Words:C/C composite, Carbon particles, Micro-fibrillated cellulose, Bending strength, Fracture toughness