202. vibration damping of composites with carbon nanontubes

Department: Structural Engineering
Faculty Advisor(s): John B. Kosmatka

Primary Student
Name: Andrew Ming Fann
Email: amfann@ucsd.edu
Phone: 818-635-1187
Grad Year: 2020

Abstract
Vibration loads are oftentimes the primary design drivers in aerospace structures. However, increasing geometric dimensions to increase strength and stiffness to survive dynamic loads can be counterproductive due to the increased mass. An alternative approach is to increase the damping of a structure. This research explores the applications of carbon nanotubes (CNT) as an embedded damping treatment for laminated composite structures. Quasi-isotropic fiberglass/epoxy plates were manufactured by wet layup. Carbon nanotubes were mechanically dispersed in the low-viscosity epoxy at various weight percentages of 0%, 2%, and 5%. The plates were tested using a PSV-400 scanning laser vibrometer in free-free boundary conditions, and the modal parameters were extracted using ME?scope. The 5 wt.% CNT plate demonstrated the highest modal damping. The CNT damping was greatest in the low frequency range (100-200 Hz). However, the CNTs significantly increased the viscosity of the epoxy, preventing the epoxy from being properly absorbed by the bleeder/breather cloth during cure. The resulting CNT-reinforced plates were thicker and heavier with increasing CNT content. The test results were used as input into a random vibration analysis of a plate in the out-of-plane direction, representative of a spacecraft panel design. The stress and acceleration power spectral densities (PSD) showed that 2 wt.% CNT provided the greatest damping benefits, decreasing the peak PSD responses by up to 11 dB relative to the neat fiberglass/epoxy plate response, while the 5 wt.% CNT plate decreased the plate response by 6 dB. The increased mass due to retained epoxy in the 5% CNT plate diminished the damping benefits, resulting in the 2% CNT plate to have the best damping-to-mass properties. Future work would investigate alternative manufacturing methods (e.g. VaRTM) to fabricate plates with embedded CNTs without the mass cost of retained resin.

Industry Application Area(s)
Aerospace, Defense, Security | Civil/Structural Engineering | Materials

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