Observation of a Lamb band gap in a polymer waveguide with periodic cross-like cavities

TL;DR

This paper demonstrates a simple, manufacturable polymer waveguide design with periodic cross-like cavities that creates large, low-frequency Lamb band gaps, confirmed through simulations and laser vibrometry measurements.

Contribution

It introduces an easy-to-fabricate cavity-based structure that effectively opens large low-frequency Lamb band gaps in a monolithic material.

Findings

Numerical simulations and measurements confirm the band gap creation.

Limited unit cell rows can effectively attenuate Lamb waves.

Design allows frequency tuning via geometric modifications.

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.