Electrophoretically Deposited Multiscale Graphene Oxide/Carbon Nanotube Construct Mediated Interfacial Engineering in Carbon Fiber Epoxy Composites

Fiber-reinforced polymer composites as a structural material have garnered tremendous interest over the past few decades. In particular, carbon fiber-reinforced epoxy (CFRE) laminates have seen extensive use in the aircraft and aerospace industry. The role of the interface between the matrix and fiber is critical and dictates the overall structural properties of the CFRE laminate. Herein, we attempt to use a commercially viable, green, and facile approach, electrophoretic deposition (EPD), to deposit covalently coupled multiscale graphene oxide (GO)/carbon nanotube (CNT) nanoconstructs onto carbon fiber (CF) fabric. The rationale behind using these hybrid conjugates is to exploit the positive synergistic effect of combining two-dimensional (2D) GO and one-dimensional (1D) CNT nanoparticles, which provide strengthening through different mechanisms resulting in a stronger matrix/fiber interface. The modified laminate with just 0.1 wt % GO/CNT content exhibited an improvement in flexural strength (FS) by 24% and interlaminar shear strength (ILSS) by 30% compared to the neat CFRE. Scanning electron microscope (SEM) micrographs confirmed uniform and homogeneous GO and GO/CNT deposition on CF. Raman, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses validate the successful functionalization of CNT and covalent coupling of GO and CNT. Atomic force microscope (AFM) and contact angle analyses indicate improved interaction between the CF and matrix. The deposition of the GO/CNT nanoconstruct on the CF improved the performance of CFREs owing to enhanced wettability, surface free energy, and surface roughness, leading to increased mechanical interlocking between the epoxy and CF at the interface. Dynamic mechanical analysis showed decreased segmental motion of epoxy chains due to improved interfacial adhesion following modification. Interesting observations were made in SEM fractography, which showed considerably different failure mechanisms in the modified CFREs. Electromagnetic interference (EMI) shielding effectiveness of -45 dB was achieved in the case of the GO/CNT-CFRE system. Electrothermal heating and de-icing performance of the modified system were also explored in this study. This versatile approach can open up new avenues for CFRE modification leading to considerably improved performance.