Bending and Delamination Resistance of CNT ‐Deposited‐Carbon Fiber‐Reinforced Epoxy Composites at Extreme Temperatures: Roles of Functionalized Nanotubes

ABSTRACT Surface modification of carbon fiber (CF) is an emerging way to improve the interfacial integrity of the carbon fiber/epoxy (CF/E) composites. In this study, Electrophoretic deposition (EPD) has been employed to deposit carbon nanotubes (CNT) onto the surface of CF to tailor the interfacial interaction in the CF/E composites. Three different types of CNTs have been considered, that is, pristine (PCNT), hydroxyl (CNT‐OH) and carboxyl functionalized (CNT‐COOH). The surface morphology of CFs following the EPD of different CNTs was examined. Flexural and short beam shear (SBS) tests were performed at three different in situ temperatures, covering a wide range, that is, cryogenic (−196°C), room (30°C) and elevated (120°C) temperatures. CNT‐COOH deposited CF/epoxy (CNT‐COOH‐CF/E) composite outperformed all other composites not only at 30°C, but also at −196°C and 120°C temperatures. CNT‐COOH‐CF/E composite exhibited ~21%, ~26% and ~36% higher flexural strength over the neat composite at 30°C, −196°C and 120°C conditions. Delamination resistance at all these temperatures was improved upon CF surface deposition by the CNTs as evident from the improved interlaminar shear strength (ILSS), obtained from SBS test. CF surface deposition with CNT‐COOH was found to be more effective than PCNT in restricting the elevated temperature (120°C) delamination, as the ILSS of CNT‐COOH‐CF/E and PCNT‐CF/E composites were found to be ~51% and ~21% higher over the neat CF/E composite. Fractographic analysis suggested micro‐deformation and failure modes associated with the composites at different test temperatures suggesting their employability at different service temperature applications.