Modeling, design and testing of a multi-cell periodic fluidic flexible matrix composite device

Open Access
Author:
Bondoux, Alexandre Franck
Graduate Program:
Aerospace Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
August 21, 2015
Committee Members:
  • Edward C Smith, Thesis Advisor
  • Christopher Rahn, Thesis Advisor
Keywords:
  • F2MC
  • vibrations
  • helicopters
  • acoustic
  • periodic
Abstract:
Vibrations have been a growing concern in recent years. Previously considered as a by-product of performances, they are now seen as an important topic to satisfy customer requests for comfort. Therefore, a lot of effort has been put in the reduction of such incommodities. Vibrations are mechanical waves that are produced by virtually any physical phenomenon. They usually transport a low amount of energy, but the human body perceives them extremely sensitively up to a few thousand Hertz. Over time, they can also provoke fatigue phenomenon in material that can lead to failure. Making the vibrations completely disappear is impossible. Instead we try to reduce them to such a level that their impact becomes negligible. Mitigating vibration effects is easy if you do not have too many constraints on the final product. However, our case will emphasize on helicopter applications, especially noise in the cabin. One could think that shielding the cabin with layers and layers of elastomeric materials would do the trick, but helicopters are very sensitive about their weight budget. Therefore, we look for devices that would reduce the vibrations with a minimal weight penalty. The present work is extending our knowledge of some fluidic devices called F2MC tubes, standing for Fluidic Flexible Matrix Composite tubes. They consist of a highly anisotropic Flexible Matrix Composite (FMC) laminate that surround a working fluid. The FMC is a composite shell having reinforcement oriented with a specific angle with respect to the longitudinal axis. These tubes have proven to be efficient at reducing vibrations in some specific configurations, being able to be tuned to target a given frequency quite accurately. As a consequence, the next move has been to try to miniaturize these tube so that they could be part of a meta-material, providing interesting structural stiffness and vibration damping abilities. The idea would be to connect back to back a given number of small sized F2MC with a small inertia track, called "cell", in a periodic structure. The damping effect would them sum up and produce a band gap centered on a frequency of choice, determined by the properties of cell.