Extraordinary Improvement in Mechanical Properties and Absorption-Driven Microwave Shielding through Epoxy-Grafted Graphene "Interconnects".

Abstract

Efficient design of electromagnetic (EM) shielding materials has emerged as a challenging research area in the past decade. To address this issue, we propose thin, lightweight, yet strong epoxy/carbon fiber (CF) composites modified with functionalized graphene oxide (GO) sheets as “interconnects”. This strategy resulted in an impressive 175% improvement in the storage modulus, a 100% enhancement in the lap shear strength, and an extraordinary 200% improvement in the shielding effectiveness at a very low GO content (0.5 wt %). First, GO was functionalized with an epoxy prepolymer (namely E-f-GO) to improve the interfacial adhesion with the matrix polymer, epoxy. As a control, epoxy nanocomposites were also prepared with modified GO. It was followed by the fabrication of CF laminates impregnated with epoxy nanocomposites. Covalent functionalization of epoxy chains on GO sheets was confirmed using various techniques like X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, atomic force microscopy, and thermogravimetric analysis. Epoxy nanocomposites were analyzed for thermal, mechanical, electrical, and adhesive strength behavior. CF laminates with epoxy nanocomposites were fabricated using vacuum-assisted resin transfer molding. The E-f-GO/epoxy/CF composite exhibited an excellent shielding effectiveness value of −70 dB, and the storage modulus was found to be >40 GPa. The modified composite showed absorption-driven shielding of EM waves and hence can be used as a highly effective EM absorber.