TENSILE PROPERTIES OF CARBON NANOTUBE/EPOXY COMPOSITE FABRICATED BY PULTRUSION OF CARBON NANOTUBE SPUN YARN

Carbon nanotubes (CNTs) possess excellent mechanical properties; thus, CNTs may have great potential for use with reinforcing polymer resin. A large amount of research has been performed on CNT-reinforced polymers. However, the challenge lies in simultaneously achieving a sufficiently high volume fraction and the preferred alignment of long carbon nanotubes in order to take advantage of the excellent mechanical properties of each CNT. Recently, CNT spinning techniques using long CNTs for producing CNT spun yarns have been developed. CNT spun yarns have higher nanotube packing fractions and better fiber alignment in spite of using long CNTs. These characteristics are ideal for the preform when fabricating high-performance composite materials. To date, few studies have been published on epoxy-based composites using spun yarns, even though epoxy is widely used for the matrix of advance composite materials. In this study, epoxy-based composites were fabricated with a bundle of single-ply spun yarns as a preform using the pultrusion technique. Pultrusion is a continuous process for manufacturing composite columns and strips with longitudinal reinforcement. This paper demonstrates that pultrusion using CNT yarns enables us to fabricate quasi-unidirectionally reinforced CNT/epoxy composites with long CNT length and high volume fraction. In the curing period of the epoxy resin, a tensile force was applied in order to investigate its effect because the spun yarn contracts in the radial direction and stretches in the axial direction due to its twisted geometry, which may increase the volume fraction and improve fiber alignment. The tensile properties of the composites were explored by using quasi-static tensile tests.