Inspection of microwave self-healing efficiency in carbon nanotube reinforced polymer composites for aerospace applications

Abstract

The aerospace industry is evolving very rapidly every day, and due to the low operational and maintenance costs, unmanned aerial vehicles (UAVs) are utilized for many duties, including imaging, patrol, surveillance, and delivery. Flying platforms prioritize effective load-carrying capacity and light weight. To achieve this, lightweight materials with sufficient strength are utilized, and design optimizations are implemented. This study investigates material development for a UAV propeller, taking into account the possible consequences of a bird strike or hard landing such as micro damage occurrence. In this study, a twin-screw extruder was used to produce hybrid composites by blending a thermoplastic, polyamide-6 (PA6) with olefin block copolymers (OBC) and carbon nanotubes (CNT). After manufacturing test specimens by injection molding, tensile and Charpy impact tests were performed. OBC increased the elongation capacity and impact resistance of the PA6 through maleic anhydride (MAH) grafting while reducing the tensile strength. CNT incorporation compensated for this drop, but it rendered the composites more brittle. More importantly, due to the CNT's microwave (MW) absorption capacity, the hybrid composites have gained self-healing properties. Extended MW exposure time and high MW powers may cause localized burning of the material, resulting in a decrease in its self-healing efficiency. Following the failure of the examined composites, SEM microscopy revealed various toughening mechanisms in the composites. The use of a modified Halpin-Tsai model to estimate the elastic characteristics of CNT-reinforced composites revealed promising results, with minimal discrepancies when compared to experimental data. Highlights: CNTs were found efficient for the self-healing behavior which is critical for improving the lifetime and planning maintenance for UAV propellers. CNT content, MW power & exposure time all impact the self-healing efficiency. Extended MW exposure time and high MW powers can cause localized burning of the material, resulting in a decrease in its self-healing efficiency. CNTs created bridge effects, ultimately leading to an enhancement in the strength of the composites. The use of a modified Halpin-Tsai model yielded good accuracy with experimental data.