Title: Observation of a Lamb band gap in a polymer waveguide with periodic cross-like cavities,
Abstract: The quest for large and low frequency band gaps is one of the principal
objectives pursued in a number of engineering applications, ranging from noise
absorption to vibration control, to seismic wave abatement. For this purpose, a
plethora of complex architectures (including multi-phase materials) and
multi-physics approaches have been proposed in the past, often involving
difficulties in their practical realization.
To address this issue, in this work we propose an easy-to-manufacture design
able to open large, low frequency complete Lamb band gaps exploiting a suitable
arrangement of masses and stiffnesses produced by cavities in a monolithic
material. The performance of the designed structure is evaluated by numerical
simulations and confirmed by Scanning Laser Doppler Vibrometer (SLDV)
measurements on an isotropic polyvinyl chloride plate in which a square ring
region of cross-like cavities is fabricated. The full wave field reconstruction
clearly confirms the ability of even a limited number of unit cell rows of the
proposed design to efficiently attenuate Lamb waves. In addition, numerical
simulations show that the structure allows to shift of the central frequency of
the BG through geometrical modifications. The design may be of interest for
applications in which large BGs at low frequencies are required.