Predicting vibration characteristics of rotating composite blades containing CNT-reinforced composite laminae and damaged fiber-reinforced composite laminae

Existing of cracks within blade structures can cause stiffness degradation and hence changes their vibration characteristics. This study investigates the vibration behaviors of rotating pre-twisted hybrid composite blades containing functionally graded carbon nanotube-reinforced composite (FG-CNTRC) laminae and damaged fiber-reinforced composite (FRC) laminae. The degraded stiffness of the cracked lamina is modeled through the self-consistent model (SCM). The blade is modeled as a shell structure that is formed by twisting a plate around its mean line. With the help of the differential geometry theory, a novel shell model has been derived to describe the kinetics of the blade. The effect of the Coriolis and centrifugal force are both presented in the formulation, which results in a damped-like free vibration system governed by a system of second-order ordinary differential equations (ODEs). Utilizing the state space technique, the system is reformulated to a system of first-order ODEs. The IMLS-Ritz method is then used for discretizing the ODEs. After carefully validating the effectiveness of the presented model through a series of comparison studies, parametric studies including CNT distribution configuration, rotating speed, geometrical parameters on the vibration responses of cross-plied composite blades are systematically examined. The vibration characteristics of angle-plied composite blades are also investigated.