Sand erosion resistance of triaxial warp-knitted composites with advanced polymer-based coatings

Fiber-reinforced composites are widely used in wind turbine blades because of their low weight and high mechanical performance, but blades operating in desert environments are vulnerable to sand erosion. In this study, polyurethane (PU), graphene oxide (GO), and multilayer PU/GO coatings were applied to triaxial warp-knitted glass-fiber/epoxy composites (TWKC). Four configurations were investigated: single-layer PU, single-layer GO, PU/GO with PU adjacent to the TWKC substrate and GO as the outermost layer, and GO/PU with the reverse sequence. Airflow–sand jet erosion tests were conducted at impact angles of 45°, 60°, and 75°. Compared with PU, GO reduced the erosion rate by 54.9%, 32.7%, and 47.8%, respectively. At 45°, TWKC-PU/GO reduced the erosion rate from 290.4 to 43.1 mg kg −1 , corresponding to an 85.2% reduction. The coating configuration with the lowest erosion rate did not necessarily exhibit the lowest maximum local erosion depth, indicating that erosion performance depended on impact angle and damage indicator. Among the multilayer configurations, TWKC-PU/GO showed favorable low-angle erosion-rate performance and overall damage morphology. These results provide guidance for designing polymer-based protective coatings for TWKC subjected to sand-particle erosion.