Experimental Linear and Nonlinear Vibration Methods for the Structural Health Monitoring (SHM) of Polymer-Matrix Composites (PMCs): A Literature Review

Round 1

Reviewer 1 Report

The article reviews current experimental vibration analysis based SHM methods for PMC's. While, the article is well designed, revisions are required to consider the article for publication.

1) In the Introduction section, 4 basic tasks in SHM is listed, but in the review article, only detection, localization and in some cases severity is discussed with out any recommendations on service life estimations. If the authors believe, this is not in scope of the review article, it would be better to add a statement at the end of introduction that the article doesn't cover the prognostic part of SHM.

2) Since the audience of the Vibration journal might not be familiar with composites, their various fiber architectures, adding an image of various fiber architectures (woven, continuous, short etc.) for the sake of the readers in section 2.1

3) Composite are inherently visco-elastic, but there is no discussion of this in the review article, except for damping methods (loss factors, damping ratio) to detect damage (linear and non linear methods). It's recommended that the authors add a subsection before damage mechanisms in composites to discuss about inherent damping in composites, which is one of their key advantages over metals. A discussion over storage and loss modulus also can provide insight of why frequency might play a key role in detecting damage using vibration analysis.

3) In section 2.2.1, it would be worthwhile for the authors to discuss the severity of damage modes with material state parameters (e.g. stiffness) or energy release (for e.g. as the fibers start to fracture, they do release a lot of energy which is why most of the nde techniques are able to pick them up easily), but where as matrix cracks might not be associated with significant energy release although lead to stiffness change (based on density of cracks) which results in natural frequency shift. This discussion could help readers in understanding some of the vibration analysis response from composite materials.

4) BVID, one of the most important damage in composites is not discussed in the review article, except where any methods were used to detect this. It is important that the authors discuss BVID in the damage section as most of the vibration analysis techniques are based on low velocity impacts.

5) in section 3, before going in to modal analysis, it is recommended to state the equation of motion, how natural frequency, and other parameters such as damping factors are calculated or include this discussion in the introduction section.

6) in section 3.2.6, figure 22 should be replaced by equations.

7) on page 21, subsection number is incorrect, should be 3.3.1, instead of 3.2.1

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

This manuscript presents a review on the experimental techniques and procedures using vibration methods for the structural health monitoring (SHM) of polymer matrix composites (PMC).  The used equipment and configurations, effectiveness, as well as the drawbacks and limitations of various methods are discussed to some extent.  The manuscript is sufficient for a review with 145 references.  Some suggestions for further improvements are below:

(1) Section 1 Introduction, the literature review is insufficient to show current research status and main challenges to define the research gap and significance to publish this review.

(2) Non-destructive testing of composite is a big topic, with more than a thousand annual publication as reported in DOI: 10.1177/1687814020913761, why the authors focused on the SHM of PMCs, how the reference papers are selected, the review methodology and innovation of this manuscript need to be specified and highlighted in Introduction. 

(3) Section 2, for different types of composite materials, it needs to be clear why current manuscript only focused on PMCs, what are the main fundamental differences for the techniques not suitable for MMCs, CMCs, etc.  The correlation of Section 2 with vibration is also weak. 

(4) The logical flow and structural division of the writing need optimization as the article tends to feel disjointed, and the sections do not always smoothly transition.

(5) Most of the discussion are shallow, focusing on the very surface and brief explanation of the reviewed methods, lack of in-depth discussion to indicate the state-of-the-art review, scientific research should go deeper.

(6) Section 4 Conclusions, artificial intelligence algorithms for SEM of PMCs have already been applied and reported in literature.

(7) Section 4 Conclusions, what are the current state-of-the-art for SEM of PMCs, what are the technical limitations and findings of this review, also suggestions for future trend need to be detailed. 

(8) Most of the references and cases cited are not up-to-date, with only one reference published in 2023. 

Quality of English is acceptable. 

Author Response

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Author Response File: Author Response.docx

Reviewer 3 Report

This article dives deep into vibration-based techniques for monitoring the health of polymer-matrix composites (PMCs). It serves as a comprehensive guide for researchers, showcasing different experimental methods and procedures. The focus starts with classic linear methods, but delves into their limitations like low sensitivity to minor damage and environmental influences. Recognizing the complexity of PMCs, the article then explores nonlinear methods, capitalizing on the material's inherent nonlinear behavior after damage occurs. By thoroughly explaining various damage mechanisms, it evaluates the effectiveness of each vibration method in detecting them.

The proposed review is definitely extensive. I stayed with a few minor comments, which are set out in the attached review.

Comments for author File: Comments.PDF

This manuscript is well written.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The authors have addressed most of the suggestions and comments, can be accepted for publication

Author Response

Thank you for your time and relevant suggestions, that helped to make a better version of this article.

Reviewer 2 Report

The authors need to be clear that they are publishing a literature review on a specific research field: it cannot be focused only on their own research laboratory, worldwide research progress is supposed to be discussed in-depth to address the significance and effectiveness of current manuscript.  

English of the manuscript is acceptable.

Author Response

Thank you for your comments.

The introduction section has been expanded thanks to your first-round comments. It now better highlights the significant rise in articles published on PMC over the past 40 years, indicating the increasing worldwide research interest in this subject matter and thereby justifying the article's exclusive focus on PMC. While our laboratory's expertise is certainly included in this topic, it is not the primary reason for the article's relevance.

Furthermore, this review article already spans 40 pages. While it would be valuable to delve into the advancements and discussions surrounding vibration methods for various materials, such an expansion would result in a substantial increase in information and references, potentially transforming the article into more of a book than an article.

To conclude, I agree with your comment about entering more in-depth into the methods and discussion, it will be very interesting. However, this is a "literature review" and not a "critical review". In our laboratory, we are slowly testing the efficiency of different vibration methods (cf the article I gave you in my first-round answer). After testing many methods in many different scenarios of testing, then it will be interesting and relevant to write a critical review.