Modal Analysis of Rotating Carbon Nanotube Infused Composite Beams
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abstract
This study presents an operational modal analysis of rotating Carbon Nanotube (CNT) infused composite beams in order to explore the effect of CNTs on the natural frequencies and damping characteristics of the composite structure during rotation. Engineering applications with rotating components made from composites often suffer from excess vibrations because of the inherent high stiffness to weight ratio of the composite material and the oscillating loads from rotation. Previous research has demonstrated that the addition of CNTs to composite resins increases the damping characteristics of the resulting material, and several of these works have suggested that CNT-infused composites may be useful in rotor design as a means of passive vibration suppression. The present work aims to address this suggestion with an experimental investigation using composite beams fabricated with CNTs embedded in an epoxy resin matrix along with several layers of reinforcing carbon fiber fabric. An experimental apparatus is designed and constructed to hold two cantilever composite beams on opposite sides of a rotating central shaft controlled via a DC servo motor and a PID control loop. White noise is generated and added to the input motor RPM signal to randomly excite the base of the structure during rotation, and the Eigensystem Realization Algorithm (ERA) is used to analyze the data measured from the vibrating beam in order to determine the modal parameters of the system. The extracted modal parameters are presented as a function of the angular speed and weight percentage CNT loading in order to gain insight into application areas involving vibration suppression in rotating composite structures such as helicopter rotors and wind turbine blades.
