Investigation on the Mesoscopic Creep Behavior and Stress Effects of Triaxial Warp-Knitted Composites

Triaxial warp-knitted composites (TWKC) are widely used in wind turbine blades owing to the excellent mechanical properties and cost-effectiveness. Due to the viscoelasticity of TWKC, it is prone to creep which may compromise structural safety. This study investigated the mesoscopic creep behavior of TWKC using nanoindentation tests. The three-point bending creep behavior of TWKC at various stress levels were analyzed, and the creep failure mechanism was clarified. The Hookean–Kelvin–Kelvin (HKK) model was established for predicting creep displacement–time curves of TWKC. The results showed that the creep resistance of the fiber is superior to that of the interface, which in turn is superior to that of the matrix. The proposed model accurately predicts the creep behavior under different stress levels with fitting correlation coefficient all above 98%. This study provides theoretical guidance for the long-term creep mechanical properties of TWKC, and thus has advantage to the optimal design of the composites.