The Effect of Argon Plasma Treatment on the Interface Properties of Aramid Fiber III /Epoxy Composites

ABSTRACT To improve the interfacial adhesion between Aramid III (AF III) fibers and epoxy composites, argon plasma was employed to modify the fiber surface. The effects of treatment power (100–400 W) on surface chemistry, morphology, wettability, single‐fiber tensile strength, and interfacial shear strength (IFSS) were investigated. Plasma treatment increased reactive functional groups and formed micro‐scale etching structures, enhancing surface chemical activity and mechanical interlocking. At 200 W, the (O + N)/C atomic ratio reached a maximum of 37.21%, and surface energy increased to 68.52 mJ/m 2 , 48.50% higher than that of the untreated fiber. The roughness parameters Ra and Rq peaked at 164 and 193 nm, respectively. Consequently, the IFSS reached 38.88 MPa, an increase of 36.37%, and the interfacial failure mode transitioned from adhesive to cohesive failure. Excessive power (≥ 300 W) led to polar group decomposition, over‐etching, and surface smoothing, deteriorating interfacial performance. This study reveals the nonlinear regulation mechanism of argon plasma treatment on the interfacial properties of AF III/epoxy composites, providing theoretical and experimental insights for interface optimization in high‐performance aramid composites.