Ultra-Wide Bandgap in Two-Dimensional Metamaterial Embedded with Acoustic Black Hole Structures
Round 1
Reviewer 1 Report
Review report on the manuscript entitled “Ultra-wide Bandgap in Two-Dimensional Metamaterial Em-2 bedded with Acoustic Black Hole Structures” by X. Iyu et al, submitted for a publication to Applied Sciences.
The paper reports a study on metamaterials aiming at their use as vibration attenuators. The authors have worked with a 2D periodic hexagonal lattice structure analyzing the dispersion relations in electrodynamic boundary value problem. They have provided the eigenstates of the proposed lattice discussing the behavior of the so-called acoustic black hole structures. The authors have checked the attenuation ability of the above structure by performing experimental study on a prototype showing the feasibility of the proposed module for applications.
I find the results interesting providing useful information on the vibration control technology based on metamaterials. The numerical work is supported by the experimental results with the conclusions are largely justified. In my opinion, the manuscript contains enough ingredients and can be published in Applied sciences.
Author Response
Response: We appreciate for your insight review and encouragements.
Author Response File: 
Author Response.docx
Reviewer 2 Report
- It is advisable to divide the "Model and Results" paragraph into three independent paragraphs "Model", "Results" and "Discussions" so that the article is better structured and consistently presented.
- How correct is it to compare the results of simulation and experiment (Figures 6 and 7) if, in simulations, the phononic crystal structure was surrounded by a PML layers, and the experimental one had free boundaries?
- It is necessary to add a more detailed description of the experiment to the text: the parameters of the experimental phononic crystal structure, the characteristics of the PZT elements.
- Give more details on how ABH was implemented experimentally. This is not clear from the text. Please add the material properties and geometrical dimensions of the structures used.
- Lines 197-198: "Compared with the traditional hexagonal lattice, the proposed design provides greater advantages in practical application". Please describe in more detail examples of practical use of the structures developed in the article. Please provide a comparative description of the results of your work with the results of other authors in recent years.
Author Response
Comment 1:
It is advisable to divide the "Model and Results" paragraph into three independent paragraphs "Model", "Results" and "Discussions" so that the article is better structured and consistently presented.
Response: Thank you for your comments. We have reorganized the paragraphs according to your suggestion. Since the results and discussion are inseparable, the results and discussion are placed under the same paragraph “Results and discussions”. The new paragraphs are listed as “Introduction”, “Model and method”, “Results and discussions” and “Conclusions”.
Comment 2:
How correct is it to compare the results of simulation and experiment (Figures 6 and 7) if, in simulations, the phononic crystal structure was surrounded by a PML layers, and the experimental one had free boundaries?
Response: Thank you for your comments. We did ignore this problem. In the revised manuscript, a simulation without PML is added and the numerical results are drawn as dark solid line in Fig. 7. Different from the simulation with PML, the material loss factor is considered in this simulation, and the results are more in line with the experimental results.
See Page 6, Lines 178-187;
Figure 7. The transmission spectrum of the finite periodic structure. Transmission comparison within 21 kHz between numerical results (blue and dark solid lines) and experimental results (red dotted line).
Comment 3:
It is necessary to add a more detailed description of the experiment to the text: the parameters of the experimental phononic crystal structure, the characteristics of the PZT elements.
Response: Thank you for your comments. We have added more details of the experiment as follows:
Figures 6(a-b) show the finite structure model (1 m×1 m) consisting of 8×8 unit cells in the frequency domain. A 5 cm thick perfect matching layer (PML) marked with blue areas surrounds the finite structure. The 0.8 m load line was excited by a harmonic force of 1 N. Figure 6(c) shows the experimental prototype made of Polycarbonate, which was processed by the high-precision milling machine. Six PZT-5H patches (25 mm×20 mm×1 mm) were pasted at three points on the left side of the prototype, and driven by a power amplifier with a sweep signal source.
See Page 5, Lines 163-171;
Comment 4:
Give more details on how ABH was implemented experimentally. This is not clear from the text. Please add the material properties and geometrical dimensions of the structures used.
Response: Thank you for your comments.
Figures 6(a-b) show the finite structure model (1 m×1 m) consisting of 8×8 unit cells in the frequency domain. A 5 cm thick perfect matching layer (PML) marked with blue areas surrounds the finite structure. The 0.8 m load line was excited by a harmonic force of 1 N. Figure 6(c) shows the experimental prototype made of Polycarbonate (Young’s modulus E=2.5 GPa, Poisson’s ratio ν=0.35, and density ρ=1100 kg/m3), which was processed by the high-precision milling machine. The parameters of the lattice are consistent with the lattice parameters in Fig. 3(a).
See Page 5, Lines 163-169;
Comment 5:
Lines 197-198: "Compared with the traditional hexagonal lattice, the proposed design provides greater advantages in practical application". Please describe in more detail examples of practical use of the structures developed in the article. Please provide a comparative description of the results of your work with the results of other authors in recent years.
Response: Thank you for your comments. The proposed design with ABHs is proved to have an ultra-wide band gap. It can be applied in the requirements, such as the battery package, which have periodicity. This structure can provide support for the battery units and has good vibration damping performance. Chen and Wang reported a class of hierarchically architected honeycombs in which structural hierarchy can be exploited to achieve prominent wave attenuation and load-carrying capabilities [28]. However, the narrow bandgap can’t meet the requirements.
[28] Y. Chen, L. Wang, Harnessing structural hierarchy to design stiff and lightweight phononic crystals, Extreme Mechanics Letters, 9 (2016) 91-96.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
no comments or suggestions
