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Article
Peer-Review Record

Experimental and Numerical Study of Vacuum Resin Infusion for Thin-Walled Composite Parts

Appl. Sci. 2020, 10(4), 1485; https://doi.org/10.3390/app10041485
by Sergey Shevtsov 1,*, Igor Zhilyaev 2, Shun-Hsyung Chang 3, Jiing-Kae Wu 4, Jyun-Ping Huang 5 and Natalia Snezhina 6
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Reviewer 4: Anonymous
Appl. Sci. 2020, 10(4), 1485; https://doi.org/10.3390/app10041485
Submission received: 31 January 2020 / Revised: 19 February 2020 / Accepted: 19 February 2020 / Published: 21 February 2020
(This article belongs to the Special Issue Physics and Mechanics of New Materials and Their Applications 2019)

Round 1

Reviewer 1 Report

This work concerning modeling of the liquid composites molding is interesting and it's an important process in industries. the authors propose a soft tool, which is able to detect the formation of dry spots or defects in fiber impregnation during vacuum infusion as the optimization module in a fluid-dynamics model solved in Comsol Multiphysics suite. This work provided sufficient information for people who are interested in modeling the process and is quite practical for real application.

Overall, this manuscript is well organized well and logic. Thus, the reviewer suggests acceptance after the following some minor revisions.

 

The introduction is too long and confused. The state of the art is exhaustively reported, however, the proposed arguments are not organically exposed. The authors should consider reorganizing the section. Please reduce the introduction should be reduced removing the too generic parts (e.g. description of the process) that are already well know and focusing it more on the main topic of the manuscript. The literature analysis on the modelling of resin infusion should be improved. Authors marginally mentioned the multiscale approach to deal with fabrics having dual scale permeability, as reported in published literature (see of example Kuentzer, Appl.Sci.Manuf. 2006, and Carlone, Appl. Compos Mater. 2014 and JAMT 2018) The approach proposed to deal with the change in pemeability during vacuum bagging infusion is not exhaustive. Reduction in porosity depends not only on the compression of fiber preform but also in the lubricant effect the resin when it wets the fibers. This phenomenon is called “wetting compaction” (see for example Acheson, Composites Part A 2004 and Carlone, Polymers 2018, and). It is reasonable neglecting this aspect in a preliminary approach, but it should be clearly mentioned. Graphs and equations should not be placed in the introduction. If they report relevant data or concepts necessary to understand the work presented in the manuscript, they should be summarized, and their contributions highlighted. If the equations are relevant to explain how the model proposed by the authors has been developed, they should placed in the section 3 of the manuscript Please, use the term “resin” instead of “binder”. It is more technically appropriate. Lines 86-90: the sentence is hardly understandable. Please rewrite. Lines 510-512 the sentence is repeated. Probably it is a typo. Please carefully check all typing and grammar errors in this manuscript.

Comments for author File: Comments.docx

Author Response

Response to 1st reviewer. Our answers and the corrections you proposed in the article are marked in red.

 Dear reviewer! We thank you very much for your comments, suggestions and corrections.

The introduction is too long and confused. The state of the art is exhaustively reported, however, the proposed arguments are not organically exposed. The authors should consider reorganizing the section. Please reduce the introduction should be reduced removing the too generic parts (e.g. description of the process) that are already well know and focusing it more on the main topic of the manuscript.

Thank you VM for your advice. Introduction was reduced, and well known information was excluded from it. The text of the article has improved in our opinion.

 

The literature analysis on the modelling of resin infusion should be improved. Authors marginally mentioned the multiscale approach to deal with fabrics having dual scale permeability, as reported in published literature (see of example Kuentzer, Appl.Sci.Manuf. 2006, and Carlone, Appl. Compos Mater. 2014 and JAMT 2018) The approach proposed to deal with the change in pemeability during vacuum bagging infusion is not exhaustive. Reduction in porosity depends not only on the compression of fiber preform but also in the lubricant effect the resin when it wets the fibers. This phenomenon is called “wetting compaction” (see for example Acheson, Composites Part A 2004 and Carlone, Polymers 2018, and). It is reasonable neglecting this aspect in a preliminary approach, but it should be clearly mentioned.

Thank you VM for you suggested papers. We referred to one article you proposed because we found very interesting information in it (lines 673-674). Of course, we are familiar with the phenomenon of wetting compaction. And we indicate this phenomenon in the text of the article (lines 72-76, 222). But we assumed that this wetting compaction is of secondary importance under vacuum infusion, when the porous preform is subjected to intense compression by external pressure. Moreover, we didn't have enough experimental data to reasonably describe his contribution to overall compaction. We intend to conduct relevant research and additions to model representations in the near future.

 

Graphs and equations should not be placed in the introduction. If they report relevant data or concepts necessary to understand the work presented in the manuscript, they should be summarized, and their contributions highlighted. If the equations are relevant to explain how the model proposed by the authors has been developed, they should placed in the section 3 of the manuscript

These suggestions were taken into account, and the text of the article was amended. Now this part of the text are replaced to the lines 343-396

 

Please, use the term “resin” instead of “binder”. It is more technically appropriate.

The term has been adjusted everywhere

 

Lines 86-90: the sentence is hardly understandable. Please rewrite.

The structure of the sentence is changed to clarify its meaning. (lines 70-72)

 

Lines 510-512 the sentence is repeated. Probably it is a typo.

Thank you very much for the careful analysis of the text. We apologize for the typo

 

Please carefully check all typing and grammar errors in this manuscript.

We tried to eliminate the grammatical errors in the text by using help of our friend, who studied in USA and works for an American company.

We are very grateful for your expertise.

Author Response File: Author Response.doc

Reviewer 2 Report

This paper presents the modeling and numerical simulation of Vacuum Assistant Resin Transfer Molding (VARTM) while focusing on predicting the formation of dry spots during resin impregnation. The numerical method proposed has novel aspects and presented in detail. The authors show the capability of the model by simulating the filling of a geometrically complex composite part. The paper can be published after minor changes.

Overall, I found the article quite informative but difficulty to read. The writing style is unnecessarily cumbersome and repetitive. I strongly suggest a careful proofreading by a professional language editor. Below, I gave a few examples of the necessary editorial changes, but there are too many to cover in this review.

Below, I took the liberty of slightly editing the abstract, which I believe, has improved its readability without loosing any substance.

This paper considers a new approach to the modeling of the vacuum infusion process for manufacturing of geometrically complex, three‐dimensional composite parts. The developed approach and numerical methods are focused on the reliable and accurate prediction and elimination the unrecoverable defects such as the dry spots. The paper presents some experimental results, which demonstrate two cases of dry spots formation in large aircraft composite panels, and analyses the reasons for the formation of these defects. Our numerical technique is based on the vacuum infusion of the liquid resin into porous preform as the two phase flow, which is described by the phase field equation coupled with the Richards equation describing the fluid motion in unsaturated soils with spatially varied pressure dependent porosity and saturation. This problem statement allowed to correctly reconstruct the resin front motion and formation of inner and outer dry spots depending on its movement. For the rapid detection of potential sites for defect formation, two indicators calculated during process simulation are proposed and tested by the numerical experiments. The auxiliary program tool has been developed in MATLAB environment to correctly detect the time of formation, localization and dimensions of the dry spots by using the results of finite element simulations

The consequence of this is a higher permeability near the inlet which is decreasing gradually towards the flow front.

Page 2: “application of temperature” needs to be “application of heat”

It is not clear what the authors are referring to in the statement: “the industrial use of the process remains insufficient.”

The following statement “… as well as leads to the layers deformation that disrupt their packing” can be revised to “… as well as leads to the layer’s deformation that disrupt their packing”, or “… as well as leads to the layer deformation that disrupt their packing”, or “… as well as leads to the deformation of layers that disrupt their packing”.

Please consider revising to: “Such problems can cause insufficient impregnation and formation of dry spots, which are not repairable.”

There are some font changes in the text, see for example, the last paragraph on page 9.

Please review the equations given for the parameters A and B on page 11 (line 357). There seems to be an inconsistent use of the symbols.

It is very difficulty to follow the equations written on page 12, mostly due to formatting and page layout.

On page 12, please revise to: “The Richards equation [48] representing fluid motion in unsaturated soils is adopted as:”

On page 13, please revise to: “However, the viscosities of the liquid resin and air differ several orders of magnitude”.

The change of air viscosity with temperature is not accounted for in this study. Air viscosity is taken as constant. Therefore, it not necessary to give Figure 12 that shows the viscosity dependence of air with temperature.

Author Response

Response to 2nd reviewer. Our answers and the corrections you proposed in the article are marked in blue.

Dear reviewer! We thank you very much for your comments and corrections.

Overall, I found the article quite informative but difficulty to read. The writing style is unnecessarily cumbersome and repetitive. I strongly suggest a careful proofreading by a professional language editor. Below, I gave a few examples of the necessary editorial changes, but there are too many to cover in this review.

We tried to eliminate all the most bulky and duplicate expressions based on your suggestions. We are very grateful to you for this valuable help.

 

Below, I took the liberty of slightly editing the abstract, which I believe, has improved its readability without loosing any substance.

This paper considers a new approach to the modeling of the vacuum infusion process for manufacturing of geometrically complex, three‐dimensional composite parts. The developed approach and numerical methods are focused on the reliable and accurate prediction and elimination the unrecoverable defects such as the dry spots. The paper presents some experimental results, which demonstrate two cases of dry spots formation in large aircraft composite panels, and analyses the reasons for the formation of these defects. Our numerical technique is based on the vacuum infusion of the liquid resin into porous preform as the two phase flow, which is described by the phase field equation coupled with the Richards equation describing the fluid motion in unsaturated soils with spatially varied pressure dependent porosity and saturation. This problem statement allowed to correctly reconstruct the resin front motion and formation of inner and outer dry spots depending on its movement. For the rapid detection of potential sites for defect formation, two indicators calculated during process simulation are proposed and tested by the numerical experiments. The auxiliary program tool has been developed in MATLAB environment to correctly detect the time of formation, localization and dimensions of the dry spots by using the results of finite element simulations.

The text of the abstract has been corrected in accordance with your suggestions.

The consequence of this is a higher permeability near the inlet which is decreasing gradually towards the flow front.

(lines ???)

Page 2: “application of temperature” needs to be “application of heat”

(lines ???)

It is not clear what the authors are referring to in the statement: “the industrial use of the process remains insufficient.”

The marked text was corrected. (lines 44-47)

The following statement “… as well as leads to the layers deformation that disrupt their packing” can be revised to “… as well as leads to the layer’s deformation that disrupt their packing”, or “… as well as leads to the layer deformation that disrupt their packing”, or “… as well as leads to the deformation of layers that disrupt their packing”. The marked text was corrected  (lines 79-80)

Please consider revising to: “Such problems can cause insufficient impregnation and formation of dry spots, which are not repairable.” The marked text was corrected (lines 84-85)

There are some font changes in the text, see for example, the last paragraph on page 9. Thank you, The font of the part you specified is fixed. (lines 277-282)

Please review the equations given for the parameters A and B on page 11 (line 357). There seems to be an inconsistent use of the symbols.

We have included a brief addendum to clarify the meaning of the sentence. (lines 308-309)

It is very difficulty to follow the equations written on page 12, mostly due to formatting and page layout.

These equations are inserted into Tables 1 - 3 for the better visibility. (lines 331-336 and 397-398)

On page 12, please revise to: “The Richards equation [48] representing fluid motion in unsaturated soils is adopted as:”

Thank you VM for your remark. (line 339)

On page 13, please revise to: “However, the viscosities of the liquid resin and air differ several orders of magnitude”.

Thank you VM for your remark. (line 388)

The change of air viscosity with temperature is not accounted for in this study. Air viscosity is taken as constant. Therefore, it not necessary to give Figure 12 that shows the viscosity dependence of air with temperature.

Corresponding sentences in the text were changed (lines 390-393), and Figure 12 was deleted.

 

Dear reviewer! We are very grateful for your expertise.

 

Author Response File: Author Response.doc

Reviewer 3 Report

Although the content of the paper is adequate and scientifically sound, the manuscript requires a detailed linguistic control.

Author Response

Dear reviewer! We tried to eliminate the grammatical errors in the text by using help of our colleague who studied in USA.

Thank you very much for your advice

Reviewer 4 Report

The paper presents an experimental, analytical and FE study of vacuum assisted resin infusion of carbon fibre parts, including those with complex geometry, in order to assess the formation of dry spot imperfections. This is a difficult problem in the industry and prediction tools are a useful measure to save time in fabrication and part design. 
1. line 328 - please replace "bizarre" with a quantitative explanation
2. line 510 - the sentence is repeated twice
3. experiments are presented then the analytical method - did you apply your analytical method to your experiments to see how well they match? If so, it would be useful to include this information to demonstrate the accuracy of the analytical method
4. conclusion section - the method is proposed to be used to assist in designing the fabrication process in a manner that will not create dry spots - in the Section 4 for the complex part did you undertake this type of analysis? If so, it would be useful to include this information to demonstrate the utility of the method with regards to the study aims
5. While the English language is not poor, I think it would benefit review from a native speaker or paid service, as in some cases it is hard to understand the authors meaning

Author Response

Response to 3rd reviewer. Our answers and the corrections you proposed in the article are marked in green.

Dear reviewer! We thank you very much for your comments and suggestions.

 

The paper presents an experimental, analytical and FE study of vacuum assisted resin infusion of carbon fibre parts, including those with complex geometry, in order to assess the formation of dry spot imperfections. This is a difficult problem in the industry and prediction tools are a useful measure to save time in fabrication and part design. 

  1. line 328 - please replace "bizarre" with a quantitative explanation

This sentence was changed to clarify its meaning:  The considered defects most often arise during the infusion of large-sized structures of complex geometry, when some parts of the convoluted front of the resin move towards each other or towards to the boundary corners of the infusing structure forming a closed loops. (lines 278-279)


  1. line 510 - the sentence is repeated twice

Thank you, repeat was deleted


  1. experiments are presented then the analytical method - did you apply your analytical method to your experiments to see how well they match? If so, it would be useful to include this information to demonstrate the accuracy of the analytical method.

In this paper we present most hard cases with complex geometry of the infused preform. So, the experimentally observed forming of the dry spots in the relatively simple preforms is out the framework of this paper that is due to its limited volume We plan to include such a comparison in our report for presentation at the next scientific conference.


  1. conclusion section - the method is proposed to be used to assist in designing the fabrication process in a manner that will not create dry spots - in the Section 4 for the complex part did you undertake this type of analysis? If so, it would be useful to include this information to demonstrate the utility of the method with regards to the study aims.

I'm sorry. The presented part of our project is only modeling, not process quality optimization. To implement such an optimization tool, we must add to the equations used those that can describe the thermal, kinetic and rheological effects to determine the evolution of the properties of the resin over several hours of its spreading.

  1. While the English language is not poor, I think it would benefit review from a native speaker or paid service, as in some cases it is hard to understand the authors meaning

Thanks for the advice. We applied to a specialist for help.

 

Dear reviewer! We are very grateful for your expertise.

Author Response File: Author Response.doc

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