Improvement of interfacial strength and fatigue stability of aramid fiber/rubber composites by constructing multiscale interphase structures

In this paper, employing nanomechanical scrutiny of aramid fibers and rubber, novel interfacial layers of different thicknesses were designed between aramid fibers and rubber using polymerizable deep eutectic solvents. The investigation explored the correlations between interfacial layers of different thicknesses and the interfacial bonding properties, fatigue resistance and hysteresis of composites. Atomic force microscopy was used to identify the changes in the thickness and modulus of the interfacial layer before and after cyclic tensile fatigue testing. The interfacial modulus decreased rapidly at different locations after the fatigue test, and was even lower than the modulus of the rubber matrix. When the thickness of the interfacial layer was similar to 1000 nm, the H pull-out force was increased by 282.3% compared with the unmodified AF, and the fatigue resistance was significantly improved and the fatigue loss was reduced from 52.39% to 14.93%. The smooth transition of modulus between aramid fibers and rubber and the appropriately thickness interfacial layer improved the mechanical properties of the composites. The microcrack extension was transferred from the surface of high modulus aramid fibers to the rubber side. In future research, this method can readily adjust the interfacial layer thickness and modulus according to different rubber types, which promotes the application of high-performance fibers in rubber.