ECCM15 - 15 TH EUROPEAN CONFERENCE ON COMPOSITE MATERIALS, Venice, Italy, 24-28 June 2012 1 MICROSTRUCTURE AND BONDING STRENGTH OF CARBON NANOTUBES DIRECTLY GROWN ON A CARBON FIBER SUBSTRATE K. J. Kim, J. Kim, G. S. Lee, S.-Y. Jeon and W.-R. Yu* 1 Department of Material Science and engineering, Seoul National University, 599 Gwanangro, Gwanak-gu, Seoul, 151-742, Republic of Korea *woongryu@snu.ac.kr Keywords: carbon nanotube, carbon fiber, interface, bonding strength Abstract Carbon nanotubes (CNTs) are directly grown on a carbon fiber (CF) surface using chemical vapor deposition to improve the interfacial properties of the CF composite. To characterize the interfacial properties quantitatively, the microstructure of the interface and the bonding strength of the CNTs on the CF surface were systematically investigated in this study. Through the observation of the microstructure by high-resolution transmission electron microscope, the interface between the CNT and the CF surface was found to consist of the covalent bonding. This interfacial structure observed was confirmed through a molecular dynamic (MD) simulation. Finally, the bonding strength of the CNTs on the CF surface was measured by separating a bundle of CNTs from the CF surface and compared with the calculated results from MD simulation, again demonstrating that the covalent bonds were formed at the interface between CF surface and CNTs. 1 Introduction Due to their high aspect ratio, large surface area, low density, and outstanding mechanical, thermal, and electrical properties, carbon nanotubes (CNTs) have stimulated a considerable amount of research, leading to numerous potential applications [1], including field-emission displays, bio-sensors, microelectrodes, and structural composites [2]. CNTs have been incorporated into these applications in a variety of forms, e.g., dispersed in a media [3], assembled in mats or yarns [4], and anchored to a substrate [5]. For the latter case, a strong interaction between the CNTs and the substrate is required to maintain good reliability for the long-term use. Recently, hierarchical structures by grafting CNTs onto a carbon fiber (CF) surface have been the subject of much research in an effort to improve the weak interface between the CF reinforcement and the matrix in CF-reinforced composites by utilizing CNT anchoring effect [6]. To characterize the effect of CNT anchoring on the interfacial shear strength of CFs, the interface between CNTs and the CF surface, including the bonding strength, should be investigated, however, few research have been conducted [7,8].