Mechanical Properties of Fibers Coated by Atomic Layer Deposition for Polymer-Matrix Composites with Enhanced Thermal and Ultraviolet Resistance

Abstract

Interfacial engineering of fiber-reinforced composites is critical to control material properties, such as mechanical strength and toughness. In this study, we utilize atomic layer deposition (ALD) as a method to conformally coat structural fiber surfaces and study the impact of these interlayers on their mechanical adhesion to polymer-matrix materials. ALD of Al2O3, ZnO, and TiO2 were applied to Kevlar® and carbon fibers, and microbond testing was performed using droplets of PMMA and Epoxy. It was observed that the mechanical force required for debonding of the polymer droplet from the coated fiber surfaces depended on the composition and thickness of the coating. Post-mortem scanning electron microscopy and energy dispersive X-ray spectroscopy for elemental analysis indicated that the ALD films remained adhered to the droplet, suggesting that the ALD/fiber interface limited the mechanical properties of the interphase region. Additionally, ALD of ZnO was demonstrated to prevent fiber degradation from ultraviolet (UV) and high-temperature thermal treatments, demonstrating a pathway towards multi-functional composite interphase engineering by ALD.