Thermoreversible Bonds and Graphene Oxide Additives Enhance the Flexural and Interlaminar Shear Strength of Self-Healing Epoxy/Carbon Fiber Laminates

Abstract

In the current era of high-strength, lightweight, and durable aircraft components, the need for carbon fiber-reinforced epoxy (CFRP) laminates is highly desired owing to their high specific strength and modulus, low coefficient of thermal expansion, and tunable properties that are unmatched by other materials. However, such components’ catastrophic failure occurs due to the interfacial defects and debonding, thereby reducing service life and economic viability. Therefore, there is a pressing need to enhance the mechanical properties of CFRPs through matrix and fiber modifications and introduce the components’ self-healing ability under a natural trigger. This study assessed the crucial role of “thermoreversible bonds” and graphene oxide (GO) “interconnects”, which worked in tandem toward significantly improving the mechanical properties and imparting self-healing properties in CFRP laminates. The laminates were fabricated with varying percentages of GO-modified epoxy matrix via vacuum-assisted resin transfer molding (VARTM) method. The carbon fibers were covalently modified with bis-maleimide (BMI) to establish a thermoreversible bond with GO at the fiber matrix interface to make interconnects. Flexural strength and interlaminar shear strength (ILSS) values for the optimized GO-modified epoxy laminates with BMI-deposited carbon fibers exhibited a significant increase of 30 and 47%, respectively. After a self-healing cycle triggered at 60 °C, they exhibited a recovery in their ILSS values up to 70%. These improvements are particularly useful for aircraft wings made up of CFRP laminates.