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TECHNICAL PAPERS

Structural and Acoustic Behavior of Chiral Truss-Core Beams

[+] Author and Article Information
A. Spadoni

 School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332

M. Ruzzene1

 School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA 30332massimo.ruzzene@ae.gatech.edu

1

Corresponding author. School of Aerospace Engineering, Georgia Institute of Technology, 270 Ferst Drive, Atlanta GA, 30332-0150.

J. Vib. Acoust 128(5), 616-626 (Mar 23, 2006) (11 pages) doi:10.1115/1.2202161 History: Received March 17, 2005; Revised March 23, 2006

This paper analyzes the structural and acoustic behavior of sandwich beams with a chiral truss-core. This particular core configuration is considered to exploit some of the unique properties of the chiral geometry and to explore their potential benefits in terms of sound-transmission reduction and vibration isolation. The chiral core is composed of circular elements or nodes, joined by ligaments or ribs. The arrangement of nodes and ribs is such that chiral assemblies exhibit in-plane negative Poisson’s ratio behavior as well as unique deformation patterns. The vibroacoustic performance of the considered beams is evaluated through a numerical model, formulated by employing dynamic shape functions derived directly from the distributed parameter model of beam elements. This formulation allows an accurate evaluation of the dynamic response of the considered structures at high frequencies with a limited number of elements. Furthermore, such a numerical model can be coupled with a Fourier-transform-based analysis of the sound radiated by the structure in a surrounding fluid medium. The structural-acoustic behavior of the proposed beams is investigated in terms of kinetic energy of the constraining layers and sound pressure levels corresponding to an incident pressure wave. A sensitivity study investigates the influence of core configuration and geometry on the beam performance. Moreover, the performance of the chiral core is compared to that of cores with “square” and hexagonal topologies. The results demonstrate the design flexibility offered by the proposed core design, whose configuration is defined by a number of independent parameters that can be modified and optimized to enhance the structural-acoustic performance of the beam.

Copyright © 2006 by American Society of Mechanical Engineers
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References

Figures

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Figure 6

Global and local reference systems, with associated element degrees of freedom

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Figure 5

Considered loading and radiation conditions for the baffled sandwich beam

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Figure 4

Hexagonal (a), reentrant (b) and square truss-core beams

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Figure 3

Unit cells of the chiral truss-core beams

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Figure 1

Chiral geometry of the unit cell

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Figure 13

Sound-transmission loss for the square core beam configurations

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Figure 14

Sound-transmission loss for hexagonal core beams: normal incidence (a) and mean value (b)

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Figure 15

Sound-transmission loss for the chiral truss-core with 1×10 cells with (a) normal incidence (b) and average incidence angle ψ

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Figure 16

Sound-transmission loss for the chiral truss-core with 2×10 cells with (a) normal incidence (b) and average incidence angle ψ

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Figure 17

Sound-transmission loss for the chiral truss-core with L∕R=0.59 (a) and L∕R=0.84 (b) for averaged wave incidence angle ψ

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Figure 7

rms velocity (a) and VTL index (b) for the square core beam

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Figure 8

rms velocity for the hexagonal (a) and reentrant (b) cores, with VTL index comparison (c)

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Figure 9

rms velocity for the 1×10 cell chiral truss-core beams for L∕R=0.59 (a) and 0.84 (b), with VTL index comparison (c)

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Figure 10

Deformed configurations for the 1×10 cell chiral truss-core beam with L∕R=0.59 at 175Hz (a), 559Hz (b), 2562Hz (c), and 3820Hz (d)

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Figure 11

rms velocity for the 2×10 cell chiral truss-core beams with L∕R=0.59 (a) and 0.84 (b), with VTL index comparison (c)

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Figure 12

Deformed configurations for the 2×10 cell chiral truss-core beam at 157Hz (a), 481Hz (b), 1580Hz (c), 3874Hz (d)

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