Vibration analysis of rotating composite blades with piezoelectric layers in hygrothermal environment

. In this study, vibration of a rotating composite blade with piezoelectric layers subjected to a tip mass in hygrothermal environment is investigated. The general composite equations for the single layer materials are expanded under varying temperature and humidity concentrations. The governing equations are derived based on the Hamilton principle based on the Euler-Bernoulli beam theory. Applying Galerkin’s procedure, the resulting equations are converted into a set of eigenvalue equations. The effects of temperature, humidity, angular velocity, fiber orientation angle, voltage and piezoelectric layers on the natural frequency of system are explored. The results show that by increasing the angular velocity, the natural frequencies increases. It was also found that increasing temperature and humidity causes a drop in the non-dimensional natural frequency. Besides, it can be concluded that heat and humidity have significant effects on the natural frequency of rotating composite blades. Applying positive and negative voltages results in a raise and drop in the natural frequency, respectively. It was also found that as the angular velocity of the composite beam increases, the non-dimensional natural frequency decreases. Furthermore, the lowest natural frequency is achieved when the tip mass is located at the end of the beam. The results show that as the fiber orientation angle increases, the natural frequencies increase which is related to enhancing the bending stiffness of the composite blades.