Mechanical and Acoustic Performance of Sandwich Panels With Hybrid Cellular Cores

2018 ◽  
Vol 140 (6) ◽  
Author(s):  
Qing Li ◽  
Deqing Yang
Keyword(s):  
Mechanical Performance ◽  
Transmission Loss ◽  
Sandwich Structures ◽  
Dynamic Performance ◽  
Sandwich Panels ◽  
Normal Incidence ◽  
Spectral Element ◽  
Sound Insulation ◽  
Insulation Property ◽  
Acoustic Performance

Sandwich structures that are embedded with cellular materials show excellent performance in terms of mechanics, electromagnetics, and acoustics. In this paper, sandwich panels with hybrid cellular cores of hexagonal, re-entrant hexagonal, and rectangular configurations along the panel surface are designed. The spectral element method (SEM) is applied to accurately predict the dynamic performance of the sandwich panels with a reduced number of elements and the system scale within a wide frequency range. The mechanical performance and the acoustic performance at normal incidence of the proposed structures are investigated and compared with conventional honeycomb panels with fixed cell geometries. It was found that the bending stiffness, fundamental frequencies, and sound transmission loss (STL) of the presented sandwich panels can be effectively changed by adjusting their hybrid cellular core configurations. Shape optimization designs of a hybrid cellular core for maximum STL are presented for specified tonal and frequency band cases at normal incidence. Hybrid sandwich panels increase the sound insulation property by 24.7%, 20.6%, and 109.6% for those cases, respectively, compared with conventional panels in this study. These results indicate the potential of sandwich structures with hybrid cellular cores in acoustic attenuation applications. Hybrid cellular cores can lead to inhomogeneous mechanical performance and constitute a broader platform for the optimum mechanical and acoustic design of sandwich structures.

scholarly journals A sustainable approach of damping treatment for aluminium honeycomb sandwich structures

2018 ◽  
Vol 233 (6) ◽  
pp. 1403-1418
Author(s):  
P Monninger ◽  
A N Thite
Keyword(s):  
Dynamic Models ◽  
Transmission Loss ◽  
Sandwich Structures ◽  
Dynamic Performance ◽  
Displacement Amplitude ◽  
Published Data ◽  
Structural Dynamic ◽  
Local Modes ◽  
Acoustic Performance ◽  
Honeycomb Sandwich

The damping plays a vital role in structural dynamic and acoustic performance of aluminium honeycomb sandwich structures. The viscoelastic damping treatment of skins is most common. An alternative, the use of sustainable cork inserts to improve the damping of cores and the whole assembly is investigated in this study. Structures with different filling degrees are analysed, as well as the optimum location for inserts is determined. The structural dynamic as well as the vibro-acoustic performance is estimated numerically. Average squared displacement amplitude reduction efficiency [Formula: see text] is defined as the target parameter for structural dynamic performance, whereas average transmission loss effectiveness [Formula: see text] is designed for vibro-acoustic performance. The structural dynamic models are validated by experimental vibration analysis, whereas the vibro-acoustic models are validated against published data. Different ways of bonding the inserts to the host structure are analysed in order to maximise damping. The highest improvement is obtained with a filling degree of 64% honeycomb voids and 9.76% increase in mass, for which an average squared displacement amplitude reduction of 35.25% and an average increase in transmission loss of 1.5 dB is achieved. The transmission loss increase in relation to the added mass is much higher than that achieved by doubling of mass in the mass law region. The introduction of cork inserts spreads the energy in local modes to a larger space, effectively decreasing the resonance amplitudes. Interestingly, damping does not increase with the number of inserts in a monotonic way and the improvement depends on the spatial distribution of inserts.

scholarly journals Vibration and Sound Transmission Performance of Sandwich Panels with Uniform and Gradient Auxetic Double Arrowhead Honeycomb Cores

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Qing Li ◽  
Deqing Yang
Keyword(s):  
Transmission Loss ◽  
Sandwich Structures ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
Bending Stiffness ◽  
Mode Shapes ◽  
Sound Insulation ◽  
Transmission Performance ◽  
Constant Weight ◽  
Honeycomb Sandwich

Auxetic mechanical metamaterials that exhibit a negative Poisson’s ratio (NPR) can be artificially designed to exhibit a unique range of physical and mechanical properties. Novel sandwich structures composed of uniform and gradient auxetic double arrowhead honeycomb (DAH) cores were investigated in terms of their vibration and sound transmission performance stimulated by nonhomogeneous metamaterials with nonperiodic cell geometries. The spectral element method (SEM) was employed to accurately evaluate the natural frequencies and dynamic responses with a limited number of elements at high frequencies. The results indicated that the vibrating mode shapes and deformations of the DAH sandwich models were strongly affected by the patterned gradient metamaterials. In addition, the sound insulation performance of the considered DAH sandwich models was investigated regarding the sound transmission loss (STL) from 1 Hz to 1500 Hz under a normal incident planar wave, and this performance was compared with that for hexagonal honeycomb sandwich panels. A programmable structural-acoustic optimization was implemented to maximize the STL while maintaining a constant weight and high strength. The results showed that the uniform DAH sandwich models with larger NPRs generally exhibited better vibration and acoustic attenuation behaviors and that the optimized gradient increasing NPR models yielded higher STL values than the optimized gradient decreasing NPR models for two specified frequency cases, with improvements of 6.52 dB and 2.52 dB and a higher bending stiffness but a lower overall STL. Thus, sandwich panels consisting of auxetic DAHs can achieve desirable vibroacoustic performance with a higher bending stiffness than conventional hexagonal honeycomb sandwich structures, and the design of gradient DAHs can be extended to obtain optimized vibration and noise-control capabilities.

Sound insulation performance of pyramidal truss core sandwich structure with frame

2021 ◽  
pp. 109963622110288
Author(s):  
Yu-Zhou Wang ◽  
Li Ma
Keyword(s):  
Mechanical Properties ◽  
Sandwich Structure ◽  
Transmission Loss ◽  
Low Frequency ◽  
Sound Insulation ◽  
Geometrical Parameters ◽  
Acoustic Performance ◽  
Truss Core ◽  
Pyramidal Truss ◽  
Wave Angle

Recently, sandwich structures have been widely used in different fields because of their good mechanical properties, but these structures are weak in acoustic performance. In this paper, by combining pyramidal truss core sandwich structure with frame, a new structure is proposed with both good mechanical properties and excellent acoustic performance at low frequency. An analytical model of the pyramidal truss core sandwich structure with frame is developed to investigate the sound transmission loss (STL) performance. Finite element method (FEM) is also used to investigate the STL performance at low frequency. The effects of the incident wave angle and the geometrical parameters on the STL of the structure are discussed.

Acoustic performance prediction of a multilayered finite cylinder equipped with porous foam media

2020 ◽  
Vol 26 (11-12) ◽  
pp. 899-912 ◽  
Author(s):  
Hamed Darvish Gohari ◽  
MohamdReza Zarastvand ◽  
Roohollah Talebitooti
Keyword(s):  
Transmission Loss ◽  
Shear Deformation Theory ◽  
Sound Transmission ◽  
Double Fourier Series ◽  
Finite Cylinder ◽  
Sound Insulation ◽  
Transverse Displacement ◽  
Sound Transmission Loss ◽  
Insulation Property ◽  
Longitudinal Modes

This paper presents an analytical model to embed porous materials in a finite cylindrical shell in order to obtain the sound transmission loss coefficient. Although the circumferential modes are considered only for calculating the amount of the transmitted noise through an infinitely long cylinder, the present study employs the longitudinal modes in addition to circumferential ones to analyze the vibroacoustic performance of a simply supported cylinder subjected to the porous core based on the first order shear deformation theory. To achieve this goal, the structure is immersed in a fluid and excited by an acoustic wave. In addition, the acoustic pressures and the displacements are developed in the form of double Fourier series. Since these series consist of infinite modes, it is essential to terminate this process by considering adequate modes. Hence, the convergence checking algorithm is employed in the form of some three-dimensional configurations with respect to length, frequency and radius. Afterwards, some figures are plotted to confirm the accuracy of the present formulation. In these configurations, the obtained sound transmission loss from the present study is compared with that of the infinite one. It is shown that by increasing the length of the structure, the results are approached to sound transmission loss of the infinite shells. Moreover, a new approach is proposed to show the transverse displacement of a finite poroelastic cylinder at different frequencies. Based on the outcomes, it is found that by enhancing the length of the poroelastic cylinder, the amount of the transmitted sound into the structure is reduced at the high frequency domain. However, the sound insulation property of the structure is improved at the low frequency region when the radius of the shell is decreased.

An improved approach for normal-incidence sound transmission loss measurement using a four-microphone impedance tube

2020 ◽  
pp. 107754632092690
Author(s):  
Zechao Li ◽  
Sizhong Chen ◽  
Zhicheng Wu ◽  
Lin Yang
Keyword(s):  
Transfer Matrix ◽  
Sound Absorption ◽  
Transmission Loss ◽  
Sound Transmission ◽  
Normal Incidence ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
The Common ◽  
Wavefield Decomposition ◽  
Insulation Performance

The main aim of this study is to introduce an improved method for determining the sound properties of acoustic materials which is more precise than the common wavefield decomposition method and simpler than the common transfer matrix method. In the first part of the article, a group of formulae for calculating sound transmission loss is represented by combining the wavefield decomposition and transfer matrix methods. Subsequently, a formula for calculating sound absorption coefficients is derived from these formulae by definition. Furthermore, the present formulae are validated by comparing the experimental results achieved with the present formulae and those results obtained by other methods recorded in published articles. Eventually, it is demonstrated that the method can accurately measure the sound insulation performance of materials and the sound absorption properties of limp and lightweight materials.

Sound Transmission Loss of Adhesively Bonded Sandwich Panels with Pyramidal Truss Core: Theory and Experiment

2015 ◽  
Vol 07 (01) ◽  
pp. 1550013 ◽  
Author(s):  
C. Shen ◽  
Q. C. Zhang ◽  
S. Q. Chen ◽  
H. Y. Xia ◽  
F. Jin
Keyword(s):  
Adhesive Bonding ◽  
Transmission Loss ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
Homogenization Theory ◽  
Sound Insulation ◽  
Sound Transmission Loss ◽  
Adhesively Bonded ◽  
Effective Elastic Constant ◽  
Standing Wave Tube

In this paper, an analytical model is developed to investigate sound transmission loss characteristic of adhesively bonded metal sandwich panels with pyramidal lattice truss cores based on 3D elasticity theory. Meanwhile, practical specimen is fabricated to conduct corresponding sound insulation experiment test via a standing wave tube method. The effective elastic constant of truss cores is derived using one homogenization theory on account of equivalent strain energy. It is found that satisfactory agreement is achieved between theoretical solutions and experiment results, and damping effect of adhesive bonding interface between facesheets and core has a great impact on transmission loss. Further parameter investigations demonstrate the significant effect of the elevation and azimuth angles of the pyramidal cores, which can be conveniently changed to tailor the acoustic performance of the sandwich panels in the whole frequency range.

Sound Insulation Performance of Finite Orthotropic Sandwich Panels

2013 ◽  
Vol 377 ◽  
pp. 12-16 ◽  
Author(s):  
Sheng Chun Wang ◽  
Wei Dong Shen ◽  
Jia Feng Xu ◽  
Pei Wen Wang ◽  
Yun Li
Keyword(s):  
Transmission Loss ◽  
Sandwich Panels ◽  
Sheet Thickness ◽  
Face Sheet ◽  
Sound Insulation ◽  
Honeycomb Sandwich ◽  
Theoretical Predictions ◽  
Core Thickness ◽  
Insulation Performance ◽  
Good Agreement

A theoretical model for calculating sound transmission loss (STL) of finite honeycomb sandwich panels is developed. The accuracy of the theoretical predictions is checked against experimental data, with good agreement achieved. Numerical analysis shows that increasing face sheet thickness can improve STL effectively, which is much more effective than increasing the core thickness. Core thickness and Youngs modulus of face sheet have evident effect on coincidence frequency, which should not be neglected when predicting STL.

scholarly journals Sound Insulation of Corrugated-Core Sandwich Panels: Modeling, Optimization and Experiment

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7785
Author(s):  
Longlong Ren ◽  
Haosen Yang ◽  
Lei Liu ◽  
Chuanlong Zhai ◽  
Yuepeng Song
Keyword(s):  
High Frequency ◽  
Sandwich Panel ◽  
Transmission Loss ◽  
Finite Size ◽  
Sandwich Panels ◽  
Sound Transmission ◽  
Coefficient Of Determination ◽  
Design Parameters ◽  
Sound Insulation ◽  
Vast Number

With the extension of the applications of sandwich panels with corrugated core, sound insulation performance has been a great concern for acoustic comfort design in many industrial fields. This paper presents a numerical and experimental study on the vibro-acoustic optimization of a finite size sandwich panel with corrugated core for maximizing the sound transmission loss. The numerical model is established by using the wave-based method, which shows a great improvement in the computational efficiency comparing to the finite element method. Constrained by the fundamental frequency and total mass, the optimization is performed by using a genetic algorithm in three different frequency bands. According to the optimization results, the frequency averaged sound transmission of the optimized models in the low, middle, and high-frequency ranges has increased, respectively, by 7.6 dB, 7.9 dB, and 11.7 dB compared to the baseline model. Benefiting from the vast number of the evolution samples, the correlation between the structural design parameters and the sound transmission characteristics is analyzed by introducing the coefficient of determination, which gives the variation of the importance of each design parameter in different frequency ranges. Finally, for validation purposes, a sound insulation test is conducted to validate the optimization results in the high-frequency range, which proves the feasibility of the optimization method in the practical engineering design of the sandwich panel.

Broadband ventilated metamaterial silencer for high reflection based on Fano-like interference

2021 ◽  
Vol 35 (06) ◽  
pp. 2150087
Author(s):  
Quanyuan Jiang ◽  
Xiaopeng Wang ◽  
Yanhui Xi ◽  
Weikang Huang ◽  
Tianning Chen
Keyword(s):  
Transmission Loss ◽  
Sound Insulation ◽  
Sound Waves ◽  
Asymmetric Transmission ◽  
Acoustic Performance ◽  
Free Air ◽  
Potential Applications ◽  
Parametric Studies ◽  
Broadband Sound ◽  
High Reflection

Conventional sound shielding structures is difficult to meet the requirements of low-to-middle frequency broadband sound insulation and free ventilation. In this paper, we propose a ventilated metamaterial silencer based on Fano-like interference, which can achieve the sound transmission loss (STL) of more than 10 dB in the range of 516–970 Hz with subwavelength thickness (0.11 [Formula: see text]) while remains an opening area ratio of 23%. The designed silencer is composed of a large central orifice and four surrounding coiling channels, making the sound waves passing through the two areas generate Fano-like asymmetric transmission spectrum and form efficient reflection to insulate sound coming from various directions. The parametric studies are also carried out to investigate the tunable acoustic performance. Experiment measurement matches well with the simulation results. In the future, the proposed silencer may have potential applications in practical environments requiring broadband sound insulation and free air flows.

Impulse Response Analysis: An Alternative Method of Measuring Sound Insulation

1996 ◽  
Vol 3 (3) ◽  
pp. 187-216 ◽  
Author(s):  
R. Lyons ◽  
B.M. Gibbs
Keyword(s):  
Impulse Response ◽  
Transmission Loss ◽  
Time History ◽  
Normal Incidence ◽  
Diffraction Theory ◽  
Optical Diffraction ◽  
Sound Insulation ◽  
Response Analysis ◽  
Impulse Response Analysis ◽  
Expected Performance

This paper investigates the use of Impulse Response Analysis methods for measuring sound insulation, in particular for elements which provide low sound insulation, such as thin panels, barriers and open screens, where standard methods are inappropriate. A practical explanation of Impulse Response Analysis and its application is given, indicating, through studies on single panels as partitions and as screens, that such elements are amenable to this method of measurement. Explanation of time history components and problems of signal capture are provided together with validation of the results by comparison with classical theory and, for screens, prediction taken from optical diffraction theory. Generally, agreement with theory is good and it is shown that the normal incidence impulse response data can be used with known empirical expressions to obtain the diffuse field transmission loss, so providing an indication of the expected performance in test laboratories and the field.

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