• PDF / 80,803 Bytes
• 6 Pages / 612 x 792 pts (letter) Page_size
• 72 Downloads / 290 Views

DOWNLOAD

REPORT

---

0924-Z05-04

Deformation Micromechanics of Carbon-Nanotube/Epoxy Composites Robert J Young, and Chih-Chuan Kao School of Materials, University of Manchester, Grosvenor Street, Manchester, Greater Manchester, M1 7HS, United Kingdom ABSTRACT The micromechanical behavior of randomly-oriented epoxy/SWNT composites has been investigated by using Raman spectroscopy. In particular, the shift of the nanotube Raman G’ band with composite strain has been monitored. It has been demonstrated that there is a strong interface and good stress transfer between the epoxy matrix and SWNTs up to about 0.4% strain but at higher matrix strains the interface appears to break down. By comparing the data in a cyclic deformation experiment, the detailed behavior of carbon nanotube composites can be determined, such as the efficiency of stress transfer and interface breakdown.

INTRODUCTION Since carbon nanotubes were first discovered by Iijima a decade ago [1] research related to the nanotubes in the fields of chemistry, physics and materials science has developed rapidly. Physicists have been interested in their remarkable electronic properties, chemists in the possibility as “nanotest-tubes” and materials scientists in their promising mechanical properties such as high stiffness, strength and resilience. Therefore, carbon nanotubes offer enormous opportunities for development and applications of new material systems for the future [2]. The atomic structure of carbon nanotubes can be imagined as a graphite sheet rolled into a cylinder shape with either open ends or the rolled sheet fixed with two caps at both ends. There are two types of nanotubes: single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs). MWNTs consist of more coaxial cylindrical rolled-up graphene sheets, which are known as concentric graphene tubes, and are separated by approximately the interlayer distance of graphite of 0.34 nm. The size of MWNTs is 2-30 nm diameter and microns in length [3]. Furthermore, each concentric graphene tube can have different chiralities and they are held together by secondary, van der Waals bonding. Three years after the discovery of MWNTs, single-walled carbon nanotubes (SWNTs) were synthesized by the same production method as MWNTs, but with additional metals such as cobalt to the carbon electrodes resulting in fine tubes with single-layer walls [4,5]. SWNTs possess a shell only one atom in thickness and can be considered as the fundamental structural unit of MWNTs [6]. The diameter of SWNTs is in the range 0.8-3 nm and they are microns in length [3]. Single-walled carbon nanotubes are most desired for the fundamental study of structure/property relationships in carbon nanotubes [2]. The specific aims of the paper are to concentrate upon an investigation by Raman spectroscopy of the interfacial behavior and stress transfer between the epoxy resin and embedded single-walled carbon nanotubes over various ranges of cyclic deformation.

EXPERIMENTAL DETAILS The single-walled carbon nanotubes (SWNTs), “bucky pearls” su