Acoustic Emission Testing and Ib-Value Analysis of Ultraviolet Light-Irradiated Fiber Composites

Round 1

Reviewer 1 Report

This work may contain interesting results. However, it needs more work before submission. I note you recently have a new publication 

https://www.mdpi.com/1996-1944/14/13/3641

How is this different from this work? There was a significant amount text that is the same in both works (mainly section 2). The novelty is not clear. The introduction also needs more explanations about why this work is needed and what the b and Ib values mean. What is different about "damage" factor from IB value apart from scaling. A few more detailed comments:

Line 43: What is meant by hits? 

Line 47: A "b-value" is mentioned but not clear what this means. Does mention "derived from the amplitude–cumulative hits distribution". Similarly "Ib" a few lines down. Perhaps a few more words to make it clearer?

Line 54: "However, the conventional b-value is not suitable for SHM of FRPs; a modified parametric value is needed, which is the subject of this research." This statement comes with no justification. Why is this needed? What is wrong with existing methods?

The introduction does not provide a statement of novelty. What is novel about this work? Where are the gaps in knowledge that this work fills?

Figure 1: The text resolution is low.

Methodology: 

Table 1: What sampling rate was used? Is this "Rate" in the table? What is "Length" - number of samples? Is 1k meant to be 1000 samples?  What preamplifier - data acquisition units were used?

Equation 2: (Where is equation 1?) The equation and font looks strange? This needs checking? It is not clear what it means.

Equation 3: Again not professional looking. Not clear what the parameters mean. 

Damage factor appears to be a claimed novelty of the paper. However, it appears to just be a scaled version of the Ib-values. 

Author Response

Thank you for your review and comment. We revised our paper reflecting your valuable comments.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors of the manuscript "Acoustic emission testing and Ib-value analysis of ultraviolet light-irradiated fiber composites" discussed the influence of glass fiber-reinforced plastics (GFRPs) composites exposed to UV radiation on their mechanical properties. For this purpose, Authors used the acoustic emission method and the Ib-value analysis. They also proposed a new parameter - the damage factor as the Structural Health Monitoring (SHM) indicator of FRP structures. Laboratory test results are promising, but need confirmation under real conditions.

The manuscript is basically well compiled, but I have a few comments:

1. The name “Figure 1"., "Figure 2.", "Figure 9." are not bold. The names of the other Figures are shown in bold. Each Figure should have the same style of writing.
2. Please check the notation of equations 2 and 3 (lines 92 and 103). In my version of the pdf file I have e.g. log_10()N where in place of () I have a square with variable f0 - generally there are no subscripts. The same for a_1, a_2, V_1, V_2 (should be a₁, a₂, V₁, V₂). By the way, why do you start numbering equations with 2? - I don't see equation 1.
3. Lines 103 (starting from text "3. Results") to 106 are redundant - I think it's the remaining fragment of another text.
4. In lline 151 you write: "High hit-per-second peaks are labelled #1-4" - in Figure 7b I can't see the labels #1, #2, #3, #4 (only red points).
5. All values on the left vertical axis (Ib-value) in Figure 9 and 10a should be given with the same accuracy (e.g. 0.015, 0.030 (instead of 0.03), 0.045, 0.060 (instead of 0.06), 0.075, 0.090 (instead of 0.09)).

Author Response

Thank you for your careful review. We revised the manuscript reflecting your valuable comment. 

Author Response File: Author Response.docx

Reviewer 3 Report

Dear authors,

This study applies acoustic emission technique to photodegradation diagnosis in order to evaluate the state of fiber-reinforced composite.  The study can be significant to industrial applications if it is successful.  The data shown in your article are not enough to explain the relationship between AE signals and photodegradation.  I recommend you, in order to re-submit your article, to discuss the correlation between the AE signals and the observation and/or analysis of cracking in detail.  The paper may be accepted for publication provided the following points were addressed:

1) Please address not only the model number of the AE sensor, but also the type and frequency band.  Why did you choose it?  Please add the explanation.

2) In your experiment, how was the AE sensor mounted to the experimental setup?  Please add the explanation.

3) If the sensor is fixed with an adhesive, is there any effect of deterioration of the adhesive surface?    Please explain it.

4) Please explain in detail the influence of background noise and the SN ratio.

5) The formula seems to be partly garbled.  Please, correct them.

6) Please elaborate on the reproducibility of the experiment and the reliability of the data.

7) Please add the microscopic observation and/or analysis of cracking.  Also, please add the discussion about the correlation between the AE signals and the results.  The change in the AE signal should be different depending on the progress of the crack.

Author Response

Thank you for your careful review. We revised the manuscript reflecting your valuable comment. 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

No text has been added to the document to better describe/justify the novelty of the paper. This needs to be added. A statement is required to specify how this work is different from other works. You should include references to literature that is similar. Please address this in the text not just in the response to the reviewer. I do not believe you have addressed my comment.

You state that:

"recent publications have focused on the analysis according to the damage mode, and this work is mainly about detecting changes in the structure's condition due to environmental degradation."

Are you stated that a novelty of this work is due to you investigating the effect of UV degradation. However, I note you have another paper which is similar to this.

"Effect of Ultraviolet Irradiation on the Material Properties and Acoustic Emission of a Fiber-reinforced Composite"

https://link.springer.com/content/pdf/10.1007/s12221-021-0423-1.pdf

I am still a bit unsure about your damage factor. You state that the starting and ending Ib-values will vary depending on the scale of the specimen and the UV environment. If one is doing measurements in the field (e.g. a wind turbine blade), will one know by what amount the Ib-values should be scaled. Would one need to do measurements in the lab to know this? However, would such have any relevance to the full size blade?

Equation 2: Check that N is defined. I had a quick look but could not see it - may have missed it.

Author Response

Thank you for your careful review. Please find the attached file.

Author Response File: Author Response.docx

Reviewer 3 Report

Nothing

Author Response

Thank you for your review.