Interface modification of carbon fiber reinforced epoxy composite by hydroxyl/carboxyl functionalized carbon nanotube

Abstract

Carbon fiber reinforced epoxy (CE) composites are already in extensive use as structural materials in aerospace and marine applications owing to their inherent high specific strength. This study proposes to further improve their mechanical properties by incorporating Hydroxyl/Carboxyl functionalized carbon nanotube (CNT-OH/CNT-COOH) nanofiller onto the surface of carbon fiber. Mechanical properties of CE composites are a strong function of interfacial bond strength between carbon fiber and epoxy matrix. In this regard, improvement of the wettability of fibers by Electrophoretic deposition technique (EPD) is proposed to enhance the interfacial bond strength and hence the properties. CNT-OH/CNT-COOH nanofiller was incorporated onto carbon fibers via EPD technique, maintaining fixed concentration of nanofiller in the bath at constant current and deposition time. Uniform deposition of nanofiller onto the carbon fibers was confirmed by Field Emission Scanning Electron Microscopy (FESEM) studies. The nanofiller deposited carbon fibers were then used for the preparation of composites by hand layup technique. This laminate was subjected to 3-point bend test for estimation of flexural properties. It was reported that CNT-COOH-CE composite exhibited an increase of flexure strength by 10% and 7% when compared to unmodified CE and CNT-OH-CE composites respectively. To evaluate the effect on glass transition temperature (Tg), Differential scanning calorimetry (DSC) was used. Also, the mode of failure in these composites were examined by fractographic study.