Abstract
It is well known that grafting carbon nanotubes (CNTs) on the reinforced fiber surface modifies fiber/matrix interface adhesion. In this study, the mechanical properties of unidirectional FRP using the CNT-grafted pitch-based carbon fiber were investigated. CNTs were grafted on the pitch-based carbon fiber surface using thermal chemical deposition (TCVD) method at 750℃. First, the single fiber tensile tests were conducted to examine the mechanical properties of the CNT-grafted carbon fibers. From the results, the mechanical properties of the CNT-grafted carbon fiber were decreased compared with as-received fiber. This degradation was caused by an exposure of the carbon fiber surface and a dissolution of iron particles into the carbon fiber surfaces under the high temperature condition of TCVD method. Moreover, static tensile tests were performed in unidirectional CFRP to investigate the mechanical properties of the CNT-grafted unidirectional CFRP. For these tests, specimens with fibers oriented at longitudinal (0°) or transverse (90°) angle from the load direction were prepared. From the results, the mechanical properties of the CNT-grafted unidirectional CFRP were decreased in longitudinal direction compared with as-received CFRP due to the degradation of the mechanical properties in CNT-grafted carbon fibers. On the other hand, it was revealed that the mechanical properties of the CNT-grafted unidirectional CFRP were increased in transverse direction compared with as-received CFRP. This enhancement was mainly due to a relaxation of stress concentration at the edge of carbon fiber by the constitution of CNT/epoxy nanocomposites around the carbon fibers.
