Preparation Of CNT/CF By Epd And Raman Study On Interfacial Micro-mechanical Properties Of Their Composites

Interface and interfacial micro-mechanical properties are crucial factors for fiber reinforced composite materials. Raman spectroscopy has a unique advantage in studying interfacial micro-mechanical properties. In this paper, CNTS/CF fibers are prepared by electrophoretic deposition, and interfacial micro-mechanical properties of carbon fiber composites are researched under two independent situations: heating and external applied stress, using Raman spectroscopy. Here, we hope to give an effective and systematic method in characterization and study of interfacial mechanics. The main contents and results are shown as followed:(1) Post-oxidation CNT can be uniformly deposited on carbon fiber surface, and that the self-strength of carbon fibers are kept. After carbon fibers are treated, the adhesive properties between epoxy and carbon fibers are improved because of deposited CNTs. Interlaminar shear strength of carbon fiber composites is increased by 46.96%, which indicates interfacial properties have been remarkably improved.(2) Raman sensitivities of CNTR/epoxy composites under heating are investigated. It is found that the high-sensitivity Raman spectrum can be acquired in the conditions as followed: CNT content in epoxy is 5%, laser power is 10%, the interface between CNT and epoxy is good, and Raman polarization angle is parallel to CNT axis.(3) The interfacial micro-mechanical behaviors of carbon fiber composites under heating are investigated for further study. By Raman mapping technique, the stress distributions at interface are acquired at different temperatures. In comparison with untreated carbon fibers, CNTs/CFs and epoxy connect closely, which results in good interfacial adhesion because of introduction of carbon nanotubes on the surface of carbon fiber. With the increment of temperature, the expansion of epoxy has an effect on interface, inducing the extrusion around the interface, and performing as the reduction of Raman wavenumber, which is about 2~3 cm-1. The stress around the interface is tensile stress, and uniformly distributes with little fluctuation, but increases gradually.(4) With external applied stress, stress transfer has intimate connection with interfacial properties in fiber composites. The deposition of carbon nanotubes improves the adhesion between carbon fibers and epoxy. By Raman mapping, stress distributions are shown at different applied strain: 0, 0.5% and 1%, respectively. For CNTS/CF, the stress around the interface increases with external applied stress increasing. When the applied strain reaches to 1%, the stress distributes in the range from 2.58 to 3.35 MPa, and stress transfer efficient reaches 1.155. But the maximum stress transfer efficient is 0.555 for untreated carbon fibers under 1% strain, and the stress distribution around the interface is between 0.5 ~ 0.9 MPa. Therefore, CNTS/CFs show outstanding stress transfer efficient.