Mechanical Vibration Testing Results of Acoustic Test Panels

This report describes the mechanical vibration testing of two graphite reinforced composite plates. The plates were tested in a free-free boundary condition up to a frequency of approximately 6 kHz. The plates were designed to assess two different damping treatments. They consisted of a 1.37 inch thick carbon epoxy structural section with a 0.13 in thick region on one side for each treatment. One plate used a conventional constrained layer design, while the other used a thin free layer of fiber reinforced urethane. The results show that while the constrain layer damped plate has a higher energy dissipation potential, it also has a reduced stiffness. There is also some localized modal behavior, which suggests it may also be reduced in strength.