A design strategy for multi-span pipe conveying fluid away from resonance by graphene platelets reinforcement

The operation of mechanical systems generates vibrations with a certain range of frequencies. Pipes conveying fluid have multiple natural frequencies. It is difficult to avoid one or more natural frequencies of pipes in the operating frequency range of the system, which can lead to resonance and fatigue failure. In this paper, a design strategy to modulate the multi-span pipe's natural frequency by reinforcing pipes with graphene platelets (GPLs) nanofiller is proposed to solve the pipe resonance in engineering. The multi-span functionally graded (FG) pipe is constructed based on an integral pipe model with GPLs uniformly or non-uniformly distributed in the metal matrix. The effective properties of the nanocomposite are determined by using the Halpin-Tsai micromechanics model and rule of mixture. Subsequently, the safety range and resonance range of the multi-span FG pipe are obtained by comparing the first tenth-order natural frequency and preserved frequency band. A comprehensive investigation on the effect of patterns, weight fraction, and geometric parameters of GPL is conducted to identify the most effective way to modulate the pipe's natural frequency. The results indicate that GPL weight fraction is able to modulate the multi-span pipe's natural frequency and safety range over a wide range. In addition, the natural frequency and safety range of the FG pipe reinforced with GPLs increase as the stiffness and number of retaining clip increase. Based on the results, a pipe design strategy with fewer retaining clips is proposed for pipes away from resonance by reinforcing pipes with GPL nanofiller. In the case of an aircraft hydraulic pipe, the natural frequency of the pipe reinforced with GPLs is far away from the preserved frequency band and without resonance in operation. In summary, the design strategy of pipe reinforced with GPLs shed important insights on reducing the vibration level of multimodal structures.