Low Velocity Impact Energy Monitoring and Recognition of Composite Laminates with Variable Thickness Based on Optical Fiber Sensor Network
Round 1
Reviewer 1 Report
The current study employs fibre Bragg grating sensors to study and analyse the impact energy on composite specimens with variable thickness. The optic sensor used collects the impulses to determine the actual impact energy. The sensing system using the optical fibre shows it is successful of recognising results which states that thickness coefficient correction method can predict the energy more accurately. The proposed method successfully identifies impact energies with minimal error on average.
The abstract is too long and requires rephrasing at certain parts. The first portion of the text in the abstract can be removed as it does not add any value to it. Also consider proper rephrasing and using simpler wording to shorten the overall length of the abstract ~250 words.
This paper does not have numbering on the left side and therefore it is difficult to track comments…I will do my best to refer to each page and it’s the duty of reviewers to track down my comments in each page…
Please avoid using first person such as we in the paper.
In page 3, what other algorithms have been used in the past similar to the ones you are using in your study and how does your differ from them?
Is there a minimum number of fibre sensors needed to improve the accuracy and robustness of the impact study when measuring the impact energy levels during different tests. Does a thicker sample for example needs more fibre sensors and vice versa?
Please avoid using short paragraphs, consider combining short ones together in one large paragraph. For example, check middle of page 4.
Section 2.3 is this really necessary to mention every single step and detail of how the process was carried out, this does not seem to add any value to the paper. Please consider removing or shortening. Only mention the main steps and remove all the extra details that make the paper read more like a report or a manual.
Page 5 can be replaced with a diagram instead of this lengthy and detailed text same as Fig.1.
Figure 2 it is not clear where the sensors are placed on the samples. Please indicate that clearly in the figure or use a bigger more detail figure to show the complete setup and sensor installation.
Did the authors calibrate the sensors before using them in the study?
Table 1 needs a reference.
For Table 2, was the choice of layup randomly chosen or based on specific needs in the study?
Figure 3 is bulky and difficult to interpret. Consider removing all the dimensions or just keep few or enlarge the image
Figure 4 is not clear and needs to be updated with a higher resolution one.
Ok here you show the location of the sensors, the question is does the location of the sensors influence the measurement process? If yes/no then did the authors prove this by testing different combination of sensor locations? Please explain and justify this point.
Figure 5-9 not very clear too please update and enlarge, use landscape view to better fit each one.
Page 13 “The larger error of the point in large thickness areas is caused by…”
The authors mention here several factors that influence the error such as reduction in spectrum amplitude and location of impact and layer thickness. Have the authors did any preliminary investigation to find optimum sensor locations with respect to the impact location in order to minimise errors in the measuring process?
Figure 10 is not clear and needs updating..
For the conclusion it is recommended to use bullet points instead of a paragraph to clearly state what was done and what was achieved and most importing findings from the impact study.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
REVIEW
on article
Low velocity impact energy monitoring and recognition of composite laminates with variable thickness based on optical fiber sensor network
Guan Lu, Tianyu Zhu, Yiming Xu
SUMMARY.
The article deals with the problem of determining the characteristics of impact on composite structures of variable thickness. This article is experimental. Impact pulse analysis is based on the Empirical Mode Decomposition method. The authors propose a signal processing technology and a fiber Bragg grating impact energy monitoring system for determining the low velocity impact load of composite laminates of variable thickness during operation. The proposed method determines the impact energy of 1-3 J with a maximum error of 14% and an average error of 4.82%.
- "In particular, the internal damage caused by low velocity impact is not easily discernible from the outside".
Internal damage is not considered in the article. The Abstract must be revised in accordance with the requirements of the journal. Editors strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: Describe briefly the main methods or treatments applied; (3) Results: Summarize the article's main findings; and (4) Conclusions: Indicate the main conclusions or interpretations. The abstract should be an objective representation of the article.
- At the end of the Introduction, it is necessary to clearly formulate the purpose of the article. What problem are you solving?
- What do you mean by low velocity impact? What speed range is being considered?
- What deformation did rates arise in this case?
- What are the advantages of your method in comparison with the known ones?
- There is no Discussion section. It is necessary to conduct a deep analysis of the results obtained and to compare the data obtained with the results of other researchers.
- Are you considering a perfectly elastic impact? Or are there local elastic-plastic deformations?
- What is the shape of the striker and the contact surface? Is it plane-plane or sphere-plane? This is very important when hitting.
In general, the article deals with interesting tasks. Still, there are many ambiguities in the article, so I recommend the article for publication after major corrections.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
All answers have been addresses and the pape can now be accepted.
Reviewer 2 Report
The article has been significantly revised and all comments have been taken into account. I recommend article for publication in present form
