Experimental and Numerical Investigations of the Vibration and Acoustic Properties of Corrugated Sandwich Composite Panels

Round 1

Reviewer 1 Report

The authors presented the investigation of the acoustic properties of two kinds of composite corrugated panels fabricated with two types of fibres (carbon and glass). The experimental and numerical results are demonstrated. The manufacturing process of corrugated-core sandwich panel is carefully described. The results of the experimental analysis were verified via the finite element method, and a parametric study was provided for the improvement of the acoustic properties of the corrugated composite panels. The conclusions and results are clearly presented.

I recommend the manuscript for publication after minor corrections:

1. The caption of Fig. 5 is not clearly written. At least, the meaning of percents is not clear from the caption.

2. A figure similar to Fig. 5b-e showing the maximum amplitudes excited in a panel is suggested to show the contribution of each mode.

Author Response

Dear reviewer,

Thanks for your carefully work. We have study the valuable comments from you carefully, and tried our best to revise the manuscript. The point to point responds to the reviewer’s comments are listed as following.

 

Reviewer 1

The authors presented the investigation of the acoustic properties of two kinds of composite corrugated panels fabricated with two types of fibres (carbon and glass). The experimental and numerical results are demonstrated. The manufacturing process of corrugated-core sandwich panel is carefully described. The results of the experimental analysis were verified via the finite element method, and a parametric study was provided for the improvement of the acoustic properties of the corrugated composite panels. The conclusions and results are clearly presented.

I recommend the manuscript for publication after minor corrections:

1. The caption of Fig. 5 is not clearly written. At least, the meaning of percents is not clear from the caption.
2. A figure similar to Fig. 5b-e showing the maximum amplitudes excited in a panel is suggested to show the contribution of each mode.

 

Response 1:

We have added the following text to explain the meaning of percents in Fig. 5.

 

(line276-288)

The error between the simulation results and the experimental results is expressed by

(7)

where  is the ith mode frequency which the reference value, and the  is the ith mode frequency which is compared to the reference frequency.

As shown in Fig. 5(b), the experimental mode of GFP is the reference value, it can be found that the mode frequencies of CFP are larger than that of the GFP, and the 4th experimental mode error is highest. The simulation mode analysis is shown in Fig. 5(c), and the simulation mode of GFP is the reference value. It can be seen that the simulation results show the same law as the experimental results. In Fig. 5(d) and Fig. 5(e), the experimental modes of panels are the reference values. It can be seen that the errors between the experimental modes and simulation modes are all less than 6%, it indicates that the results obtained from the proposed FE model showed a very good agreement to the experimental results.

 

Response 2:

We have added the bars into the simulation results in Fig. 5(a), so the deformation of different mode can be expressed more clearly. The new figure is as follows. The purpose of this paper is investigating the effect of design parameters on the modes of the panels, however, the vibration transmission properties of the panels are not studied. Therefore, the contribution of modes on the vibration amplitude is not studied here. However, the question from the reviewer is very valuable. The sandwich panel has different structure and properties in different in-plane direction, which will inevitably lead to different vibration transmission properties. This is also an important vibration performance of composite plate, and we will investigated this in the future work. 

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,
In the beginning, I would like to congratulate you on the very interesting paper with a comprehensive approach allowing you to see not only the analytical and numerical solutions to the problem but also very professionally performed experimental tests. Below I would like to point out some elements worth improving.

A)    General remarks
1.    The main question that must be answered is how the authors' approach is different from typical case study tests. The reviewer is not convinced about the novelty of the study. In the last paragraph of the introduction, the authors, are providing the aim and scope of the study but do not present in a strong manner what is the novelty of the presented case. Please make sure this is presented both here and later in the conclusions.
2.    Article is clearly written and easy to follow. The authors give relevant references which are linked to their study. It must be pointed out that the majority of the references are from Chinese authors. It is suggested to look also on the worldwide literature. Some additional possibilities of references can be found in the following points but it is also suggested to add or change some references to present the achievements of other scientific centres.
3.     The abstract is well written introducing the basic overview of the paper. It is also written in a way that even a person not familiar with the topic can understand what the authors are proposing in their research. However, some sentences are difficult to follow and suggest checking them with a native speaker.
4.    The introduction provides basic background and overview of the methods used by the authors. However, the introduction is not presenting the state of the art for some measurement techniques in the case of modal analysis. Look at point 6.
5. Chapter  2 is well written and no significant changes are required.
6.    The research design is appropriate with the methodology explained and presented. The approach of using springs to mimic the free boundary condition is correct. Another way is using elastic strings. The missing element is information on sensors (accelerometers) and actuators (modal hammers). What were the models of sensors, accuracy, and signal acquisition settings? It must be pointed out that the authors are using a classical approach to modal analysis. This element should be described in the introduction. Additionally, modern, contactless methods should be evaluated for state of art analysis in the introduction. Especially the use of 3D Laser Vibrometry (perfect for free-free conditions where the sample can be supported on elastic strings) and Digital Image Correlation (DIC). You can use example for measurements on composite truss M.Guinchard "Non-invasive measurements of ultra-lightweight composite materials using Laser Doppler Vibrometry system" Proceedings of the 26th International Congress on Sound and Vibration (ICSV19) and modal analysis on steel blades "Quality Assurance and Control of Steel Blade Production Using Full Non-Contact Frequency Response Analysis and 3D Laser Doppler Scanning Vibrometry System" 2021 11th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems. The use of 3D laser vibrometry is especially beneficial for users who want to evaluate and directly connect measurements and simulations. In the case of DIC, you can use Emilio Di Lorenzo et. Al, “Full-Field Modal Analysis by Using Digital Image Correlation Technique”
Moreover, DHDAS is not well recognized worldwide and the sentence in lines 170-172 can be misleading. Please indicate if this is the acquisition system or the software. Please make an informative statement that this is in fact dynamic signal acquisition and analysis software system. Moreover, the specification of data acquisition parameters and signal processing is also required for the possibility of future cross-checks of this research.
7.    The simulation methods are described in detail. 
8.    There are no significant remarks to the results which are clearly presented.
9.     In the case of the conclusions the authors emphasize what was done in the paper and the result presentation. It is more discussion of the results than real conclusions. The reviewer would suggest distinguishing both elements (discussion of results and conclusions). The conclusions should emphasize the usefulness of the results and their application. This should also inform the reader on what was the novelty of the study and are possible next steps. If the authors decide to leave the conclusions as they are I would suggest adding a few sentences on this matter.

B)    Item remarks
All figures and pictures are clear. No significant changes are required or suggested.

C)    Conclusions
The article is clear and interesting with no significant errors found in the research. Both methodology and results acquisition is correct. However, some changes have to be made in case of explanation of equipment used, and signal parameters. Moreover, some additional state-of-the-art analysis of modern modal analysis testing techniques has to be incorporated in the introduction. At the current stage, the reviewer asks for major changes in those areas and will be happy to accept the paper after sufficient corrections.
 

Author Response

Dear reviewer,

Thanks for your carefully work. We have study the valuable comments from you carefully, and tried our best to revise the manuscript. The point to point responds to the reviewer’s comments are listed as following.

 

Dear authors,

In the beginning, I would like to congratulate you on the very interesting paper with a comprehensive approach allowing you to see not only the analytical and numerical solutions to the problem but also very professionally performed experimental tests. Below I would like to point out some elements worth improving.

1. A)    General remarks

Comment 1.

 The main question that must be answered is how the authors' approach is different from typical case study tests. The reviewer is not convinced about the novelty of the study. In the last paragraph of the introduction, the authors, are providing the aim and scope of the study but do not present in a strong manner what is the novelty of the presented case. Please make sure this is presented both here and later in the conclusions.

 

Response 1:

At the end of the introduction,the following text is added for emphasizing the novelty of this work.  

(line 138-143) On the basis of the model validation, a parametric study on the vibration and acoustics properties of the corrugated composite panels was performed. The coupling effect of the vibration and acoustic properties is revealed and the sensitive design factors to the vibration and acoustic properties of the panel are found, which is the main novelty of the present work. This work can provide a fundamental support for the comprehensive design of vibration and acoustics of the composite sandwiched panel.

 

Comment 2.

Article is clearly written and easy to follow. The authors give relevant references which are linked to their study. It must be pointed out that the majority of the references are from Chinese authors. It is suggested to look also on the worldwide literature. Some additional possibilities of references can be found in the following points but it is also suggested to add or change some references to present the achievements of other scientific centres.

Response 2:

In the paper, we have added some new references to present the achievements of other scientific centres.

 

(line 73-83) Arunkumar et al. [29] investigated the influences of electric and magnetic potential on the vibro-acoustic response of the different types of truss core and honeycomb core sandwich panels, and provided an exact solution for a vibro-acoustic response of Magneto-electro-elastic (MEE) composite plate and sandwich panels with MEE facings. Mohammadi et al. [30] used the Kirchhoff-Love shell theory to model the kinematic behavior of sinusoidally corrugated panels with a variable radius of curvature, and studied the effects of different configurations of carbon nanotubes and various geometrical parameters such as corrugation amplitude, number of corrugation units. Furthermore, panel aspect ratio are presented on the natural frequency and dynamic response of the sinusoidally corrugated functionally graded carbon nanotube reinforced composite panels.

 (line 86-94)In recent years, in order to solve the problems encountered in the application of traditional modal testing methods (for example, the sensor must contact the measured object, the force hammer is easy to damage the measured object, et al), many new modal testing methods and equipment, such as Laser Doppler Vibrometry system [31-32] and Digital Image Correlation Technique [33], have been developed. These work presents the use of non-destructive, non-contact experimental modal analysis using the single or multipoint approach for measurement over the surface of the product, and enable modal testing to be performed in more working environments.

(line 106-118) Shahsavari et al. [39] presented an analytical study on the sound wave propagation across a sandwich cylindrical shell with a corrugated core filled with porous materials, and investigated the vibroacoustic effects of various parameters, such as porosity, types of the porous materials, the thickness of the corrugated core, structural damping factor, incident angle, and Mach number of the external flow. Jin et al. [40] proposed a perforated metastructure combining fish-belly panels and a corrugated sandwich structure for broadband sound absorption, and developed an effective impedance theory to study the relationship between sound absorption performance and geometric factors. Luo et al. [41] designed 49 kinds of aramid honeycomb sandwich panels by the orthogonal test method, and tested their sound insulation properties, furthermore, predicted the sound insulation performance of aramid honeycomb sandwich panel based on artificial neural network.

 

 

Comment 3.

 The abstract is well written introducing the basic overview of the paper. It is also written in a way that even a person not familiar with the topic can understand what the authors are proposing in their research. However, some sentences are difficult to follow and suggest checking them with a native speaker.

Response 3:

The grammar of this paper has been modified by the corresponding author Prof. Tian Zhao, who received his Ph.D. from Delft University of Technology.

 

Comment 4.

The introduction provides basic background and overview of the methods used by the authors. However, the introduction is not presenting the state of the art for some measurement techniques in the case of modal analysis. Look at point 6.

Response 4:

We added some references to introduce the new modal testing methods, the text is as follows.

(line 86-94)In recent years, in order to solve the problems encountered in the application of traditional modal testing methods (for example, the sensor must contact the measured object, the force hammer is easy to damage the measured object, et al), many new modal testing methods and equipment, such as Laser Doppler Vibrometry system [31-32] and Digital Image Correlation Technique [33], have been developed. These work present the use of non-destructive, non-contact experimental modal analysis using the single or multipoint approach for measurement over the surface of the product, and enable modal testing to be performed in more working environments.

 

Comment 5.

Chapter  2 is well written and no significant changes are required.

Response 5:

Thank you for your work.

 

Comment 6.

The research design is appropriate with the methodology explained and presented. The approach of using springs to mimic the free boundary condition is correct. Another way is using elastic strings. The missing element is information on sensors (accelerometers) and actuators (modal hammers). (1)What were the models of sensors, accuracy, and signal acquisition settings? It must be pointed out that the authors are using a classical approach to modal analysis. This element should be described in the introduction. 

(2)Additionally, modern, contactless methods should be evaluated for state of art analysis in the introduction. Especially the use of 3D Laser Vibrometry (perfect for free-free conditions where the sample can be supported on elastic strings) and Digital Image Correlation (DIC). You can use example for measurements on composite truss M.Guinchard "Non-invasive measurements of ultra-lightweight composite materials using Laser Doppler Vibrometry system" Proceedings of the 26th International Congress on Sound and Vibration (ICSV19) and modal analysis on steel blades "Quality Assurance and Control of Steel Blade Production Using Full Non-Contact Frequency Response Analysis and 3D Laser Doppler Scanning Vibrometry System" 2021 11th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems. The use of 3D laser vibrometry is especially beneficial for users who want to evaluate and directly connect measurements and simulations. In the case of DIC, you can use Emilio Di Lorenzo et. Al, “Full-Field Modal Analysis by Using Digital Image Correlation Technique”

(3)Moreover, DHDAS is not well recognized worldwide and the sentence in lines 170-172 can be misleading. Please indicate if this is the acquisition system or the software. Please make an informative statement that this is in fact dynamic signal acquisition and analysis software system. Moreover, the specification of data acquisition parameters and signal processing is also required for the possibility of future cross-checks of this research.

 

Response 6:

We have added the text to describe the information of the accelerometer sensor and modal hammer. And the DHDAS is a dynamic signal acquisition and analysis software system. Three new  references are added to introduce the novel modal methods and equipment. The text is as follows.

Response to (1) and (3)

(line 210-217) In this paper, the accelerometer sensor and modal hammer are from Donghua Testing Technology Co., Ltd. The accuracy of the accelerometer is 1.075 mV/(m▪s2) and the frequency response range is 1-10000Hz. The accuracy of modal hammer is 2.118 mV/N and the working range is 1-5000N. The sampling frequency for the modal test is 2000Hz. The PolyLSCF is used to fit the frequency response function. The dynamic signal, mode shapes, mode frequencies and damping ratios are obtained using the dynamic signal acquisition and analysis software system, DHDAS, from Donghua Testing Technology Co., Ltd.

 

Response to (2)

(line 86-94) In recent years, in order to solve the problems encountered in the application of traditional modal testing methods (for example, the sensor must contact the measured object, the force hammer is easy to damage the measured object, et al), many new modal testing methods and equipment, such as Laser Doppler Vibrometry system [31-32] and Digital Image Correlation Technique [33], have been developed. These work presents the use of non-destructive, non-contact experimental modal analysis using the single or multipoint approach for measurement over the surface of the product, and enable modal testing to be performed in more working environments. 

 

[31] L. Scislo, M. Guinchard, Non-invasive measurements of ultra-lightweight composite materials using Laser Doppler Vibrometry system, 26^th International Congress on Sound and Vibration, (2019).

[32] L. Scislo, Quality Assurance and Control of Steel Blade Production Using Full Non-Contact Frequency Response Analysis and 3D Laser Doppler Scanning Vibrometry System, 2021 11th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications (IDAACS) IEEE, 1 (2021).

[33] E.D. Lorenzo, P. Lava, R. Balcaen, et al., Full-field modal analysis by using digital image correlation technique, Rotating Machinery, Optical Methods & Scanning LDV Methods, 6 (2020) 119-130.

 

 

 

 

Comment 7.

The simulation methods are described in detail. 

Response 7:

Thanks for your work.

 

 

Comment 8.

There are no significant remarks to the results which are clearly presented.

Response 8:

We have added some text to summary the results in the parametric analysis.

 

(line 409-411) In summary, the layer thickness of the surface resin is the most sensitive design factor to the vibration properties of the sandwich corrugated panel, and changing the layer thickness of surface resin is easy to operate in engineering.

 

(line 461-465) In summary, the modulus of resin is the most sensitive factor to the initial frequency of the panel’s resonant sound transmission, which can be easy to operate by changing the layer thickness of surface resin in engineering. The thickness of fiber cloth is the most sensitive factor to the STL of the sandwich corrugated panel, which can be easily to operate by changing the layer number of the fibre cloth in engineering.

 

Comment 9.

 In the case of the conclusions the authors emphasize what was done in the paper and the result presentation. It is more discussion of the results than real conclusions. The reviewer would suggest distinguishing both elements (discussion of results and conclusions). The conclusions should emphasize the usefulness of the results and their application. This should also inform the reader on what was the novelty of the study and are possible next steps. If the authors decide to leave the conclusions as they are I would suggest adding a few sentences on this matter.

Response 9:

(line 472-490) The conclusions are corrected as follows, and some few sentences are added to summary the research.

(1)Low-order mode frequencies are greatly influenced by the resin layer on the panel surface, despite of the extremely low thickness.

(2)The density of fibre is the main factor affecting low-order modes of composite sandwiched panels. In contrast, the effect of fibre modulus on the low-order modes is slight.

(3)The layer thickness of the surface resin is the most predominant factor affecting  the initial frequency of the panel’s resonant sound transmission.

(4)The sound transmission loss (STL) of the sandwiched panel is mainly following the mass law. Increasing the fibre volume fraction or the fibre density can significantly increase the STL property of the corrugated panels. However, this is achieved at the cost of a decrease of the resonance frequency. Fortunately, this can be compensated by increasing the layer thickness of the surface resin. Increasing the foam density also improves the STL, while this tends to significantly increase the weight of the entire panels.

In summary, the thickness of fibre cloth, the fibre density and the layer thickness of the surface resin are the most sensitive design factors to the vibration and acoustic properties of the lightweight sandwich corrugated panel, and  the vibration and acoustic properties of composite panels can be flexibly designed by different parameter combinations.

 

 

 

1. B)    Item remarks

All figures and pictures are clear. No significant changes are required or suggested.

Response :

Thanks for your work.

 

 

1. C)    Conclusions

The article is clear and interesting with no significant errors found in the research. Both methodology and results acquisition is correct. However, some changes have to be made in case of explanation of equipment used, and signal parameters. Moreover, some additional state-of-the-art analysis of modern modal analysis testing techniques has to be incorporated in the introduction. At the current stage, the reviewer asks for major changes in those areas and will be happy to accept the paper after sufficient corrections.

Response :

Thanks for your work. I have answered your valuable comments point by point.

 

Author Response File: Author Response.docx

Reviewer 3 Report

In reviewer's opinion, the paper can be recommended for publication in Journal of Applied sciences with addressing the reviewer's comments listed below:

- The most recent references (2021-2022) should be added to the introduction section.

- Section 4. Numerical simulation: how the sensitivity of the mesh elements is tested in the numerical model.

- The material behavior model chosen for the sandwich panel is not well described.

- The interaction between the different layers of the sandwich panel is not described in the text.

Author Response

Dear reviewer,

Thanks for your carefully work. We have study the valuable comments from you carefully, and tried our best to revise the manuscript. The point to point responds to the reviewer’s comments are listed as following.

 

Review 3

In reviewer's opinion, the paper can be recommended for publication in Journal of Applied sciences with addressing the reviewer's comments listed below:

Comment 1

The most recent references (2021-2022) should be added to the introduction section.

Response 1:

We have added 7 new references to the introduction section.

 

[29] M.P. Arunkumar, V. Bhagat, Q. Geng, et al., An exact solution for vibro-acoustic response of smart sandwich panels with MEE composite Layer, Compos. Struct. 286 (2022) 115201.

[30] H. Mohammadi, A.R. Setoodeh, A.P. Vassilopoulos, Isogeometric Kirchhoff-Love shell patches in free and forced vibration of sinusoidally corrugated FG carbon nanotube-reinforced composite panels, Thin Wall Struct. 171 (2022) 108707.

[32]L. Scislo, Quality Assurance and Control of Steel Blade Production Using Full Non-Contact Frequency Response Analysis and 3D Laser Doppler Scanning Vibrometry System, 2021 11th IEEE International Conference on Intelligent Data Acquisition and Advanced Computing Systems: Technology and Applications (IDAACS) IEEE, 1 (2021).

 

[39] H. Shahsavari, M. Kornokar, R. Talebitooti, et al., The study of sound transmission through sandwich cylindrical shells with circumferentially corrugated cores filled with porous materials, Compos. Struct. 291 (2022) 115608.

[40]Y. Jin, Y. Yang, Z. Wen, et al., Lightweight sound-absorbing metastructures with perforated fish-belly panels, Int. J. Mech.l Sci. 226 (2022) 107396.

[41]Z. Luo, T. Li, Y.Yan, et al., Prediction of sound insulation performance of aramid honeycomb sandwich panel based on artificial neural network, Appl. Acous. 190 (2022) 108656.

 

[47] H. Ji, B. Han, L. Cheng, et al., Frequency attenuation band with low vibration transmission in a finite-size plate strip embedded with 2D acoustic black holes, Mech. Syst. Signal Pr. 163 (2022) 108149.

 

 

 

 

 

 

 

Comment 2:

Section 4. Numerical simulation: how the sensitivity of the mesh elements is tested in the numerical model.

 

Response 2:

In the paper, we have added some sentences and a new reference to the section 4.

 

(line 247-249) According to the literature [47], at least ten elements per local wavelength were ensured at the highest frequency in the simulation analysis. Therefore,the element size was set to be 2 mm to guarantee the precision of analysis.

 

[47] H. Ji, B. Han, L. Cheng, et al., Frequency attenuation band with low vibration transmission in a finite-size plate strip embedded with 2D acoustic black holes, Mech. Syst. Signal Pr. 163 (2022) 108149.

 

 

Comment 3

The material behavior model chosen for the sandwich panel is not well described.

Response 3:

The text about the material behavior is corrected as follows.

(line 145-155)In this paper, the corrugated composite panel is a sandwiched panel composed of reinforced fibre cloth, resin and foam strips. The fibre cloth and foam are bonded together by the resin, and the cured resin is also an important part of the corrugated composite panel. In the research, two types of plain woven fabric fibre cloths, i.e. T300 carbon fibres and S-PC/EWR400 glass fibres, were utilized to fabricate different corrugated composite panels. The related material properties of the two fibre cloths were listed in Table 1, which were supplied by Hebei Optfilm Composite Co. Ltd. The lightweight M60 PVC foam strips were used to maintain the corrugate shape, and it was supplied by Sino Composite. The MERICAN 30-200P vinyl epoxy resin was supplied by Sino Polymer, China. The related material properties of the foam and resin are listed in Table 2.

 

 

 

Comment 4

The interaction between the different layers of the sandwich panel is not described in the text.

 

Response 4:

We have added some text to describe the interaction between the different layers of the sandwich panel.

(line 145-148)In this paper, the corrugated composite panel is a sandwiched structure composed of reinforced fibre cloth, resin and foam strips. The fibre cloth and foam are bonded together by the resin, and the cured resin is also an important part of the corrugated composite panel.

(line 245-247)The components were assembled by using a merge technique which makes the joint surface between components have common nodes.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Authors,

Thank you for revising the previous version of the manuscript.

Concerning the previous comments, all the points were addressed and the reviewer can state that the paper is of sufficient quality for publication in the present form.

Best regards,

The reviewer