In Situ FBG Monitoring of a Henequen-Epoxy Biocomposite: From Manufacturing to Performance

Round 1

Reviewer 1 Report

In this paper, the authors introduced the in-situ instrumentation from manufacturing to loading of a henequen fiber woven-bioepoxy composite. The track curing behavior of the biolaminate by vacuum assisted resin infusion (VARI) was continuously monitored by fiber bragg gratings (FBGs). And the instrumented composite was later tested mechanically under bending. Experimental results show that micro-deformations were detected as a consequence of curing residual stresses and the FBG data had similarity with the strain calculated according to the standard. The inscriptions of the experimental results are well described, but there are still the following problems. The specific comments are given as followed:

1. The introduction of this paper mainly introduces the rise and application of composite materials, the importance of detecting the structural integrity of new bio-materials, and the detection method of Bragg gratings. However, the author's description is too cumbersome. It should be more concise and brief to let readers quickly understand the author's intent.
2. Figure 1 should fully demonstrate the FBG fiber optic monitoring VARI device fabricated from bio-composites, and the devices mentioned in Section 2.4 should be marked in the figure.
3. In Figure 3(b), it is impossible to see how to perform the bending test of the composite material, and the details of the picture should be added.
4. From pictures 4 to 14, the units of the Microstrain are “me”, but the units during the experimental analysis are “me”, please explain the reason?
5. Lin210-214, it is hard for readers to understand the statement “It can be noticed the decrease ... the exothermic reaction contributes to the variation in the microstrains monitored by the FBG, as shown in Figure 10”. As shown in Fig.10，there is a more notable variation in the microstrains sensed by the FBG at the beginning, then, smooth,and it changes drastically at last. Please give the explanation.

Author Response

In this paper, the authors introduced the in-situ instrumentation from manufacturing to loading of a henequen fiber woven-bioepoxy composite. The track curing behavior of the biolaminate by vacuum assisted resin infusion (VARI) was continuously monitored by fiber bragg gratings (FBGs). And the instrumented composite was later tested mechanically under bending. Experimental results show that micro-deformations were detected as a consequence of curing residual stresses and the FBG data had similarity with the strain calculated according to the standard. The inscriptions of the experimental results are well described, but there are still the following problems. The specific comments are given as followed:

 

The introduction of this paper mainly introduces the rise and application of composite materials, the importance of detecting the structural integrity of new bio-materials, and the detection method of Bragg gratings. However, the author's description is too cumbersome. It should be more concise and brief to let readers quickly understand the author's intent.

 

1. The authors appreciate the kind comments of the Reviewer. The introduction section was modified to be more concise about the goal of the manuscript. Thank you.

 

Figure 1 should fully demonstrate the FBG fiber optic monitoring VARI device fabricated from bio-composites, and the devices mentioned in Section 2.4 should be marked in the figure.

In Figure 3(b), it is impossible to see how to perform the bending test of the composite material, and the details of the picture should be added.

 

1. A full description on the figures is set.

 

 

From pictures 4 to 14, the units of the Microstrain are “me”, but the units during the experimental analysis are “me”, please explain the reason?

 

1. All units are properly fixed in the figures

 

Lin210-214, it is hard for readers to understand the statement “It can be noticed the decrease ... the exothermic reaction contributes to the variation in the microstrains monitored by the FBG, as shown in Figure 10”. As shown in Fig.10，there is a more notable variation in the microstrains sensed by the FBG at the beginning, then, smooth,and it changes drastically at last. Please give the explanation.

 

1. Paragraph was rewritten.

Reviewer 2 Report

1. Table 1. A table with one component does not make sense, it should be deleted, and the characteristics should be indicated in brackets in the description in the appropriate section and with the specified reference to the literature.
2. The same with tables 2-4.
3. In the Materials and Methods section, the description of technical details should be limited, and all figures should be transferred to the results and discussion.

Author Response

Table 1. A table with one component does not make sense, it should be deleted, and the characteristics should be indicated in brackets in the description in the appropriate section and with the specified reference to the literature.

The same with tables 2-4.

 

1. All tables are now inserted in the main text.

 

In the Materials and Methods section, the description of technical details should be limited, and all figures should be transferred to the results and discussion.

 

1. Technical details are summarized. Figures concerning the results of the experimentation are included in the results and discussion.

 

Reviewer 3 Report

This paper reports a study about an in-situ FBG monitoring of a henequen-epoxy biocomposite. I have some comments.

1- Introduction: when is mentioned "FBGs are fabricated from the inscription of periodic or quasi-periodic refractive index variations of a SiO2 fiber optic core..." It is incompleted. Please add some words about plastic fiber optic core and not only about SiO2, since both are very used in sensors. Please read and refer: a) Optics express 25 (8), 9028-9038, 2017; Optics Express 26 (2), 2013-2022, 2018. It is critical to mention it to be more complete.

2- Section 2.3: How the FBGs were inscribed? What laser used, frequency, time, etc? How many FBGs were tested? How about a typical spectrum of the FBG used?

3- Figs. 4 to 12: The results are only for one FBG? How many sensores were tested? How about error associated?

 

4- Fig. 14: these results were tested for more than one cycle? Please include more data to discuss and undetstand the repeatability.

Author Response

This paper reports a study about an in-situ FBG monitoring of a henequen-epoxy biocomposite. I have some comments.

 

1- Introduction: when is mentioned "FBGs are fabricated from the inscription of periodic or quasi-periodic refractive index variations of a SiO2 fiber optic core..." It is incompleted.

Please add some words about plastic fiber optic core and not only about SiO2, since both are very used in sensors. Please read and refer: a) Optics express 25 (8), 9028-9038, 2017; Optics Express 26 (2), 2013-2022, 2018. It is critical to mention it to be more complete.

 

1. A paragraph citing these references has been added.

 

2- Section 2.3: How the FBGs were inscribed? What laser used, frequency, time, etc? How many FBGs were tested? How about a typical spectrum of the FBG used?

 

1. Only 1 FBG was inscribed. Preset conditions from the MicronOptics si155 interrogator were used.

 

3- Figs. 4 to 12: The results are only for one FBG? How many sensors were tested? How about error associated?

 

1. We have tested 2 more FBG sensors each one on different biocomposites (Henequen+EVO+graphene particles) and (Henequen+Green epoxy), sensing from infusion to bending load. Those results are similar and will be published later on.

 

4- Fig. 14: these results were tested for more than one cycle? Please include more data to discuss and understand the repeatability.

 

1. Bending test was repeated 3 times, with minimal changes. As lines were undistinguishable, authors preferred to plot only one case.

 

Reviewer 4 Report

The presented article discusses the results of a well-staged experiment on the study of in-situ instrumentation from manufacturing to loading of a Henequen fiber woven - bioepoxy composite.

The introduction quite fully reflects the methods and means of testing the materials under consideration using fiber Bragg gratings. The setting of the experiment and the measurement methods are set very scrupulously and clearly. Each result obtained is discussed in detail, all the features of the research are given and discussed. The conclusion fully reflects the subject of the article and the significance of the results obtained. The use of a high-tech interrogator removes all questions about the given graphical dependencies.

However, taking into account the well-known relationship between the wavelength and strain, which do not go beyond the limit values, I ask the authors to evaluate whether it is really necessary to give two graphs for both the wavelength and the strain. Solving this issue is my recommendation. If the authors want to leave the graphs unchanged, for example, to demonstrate the possibilities of the method, namely, for chemists, then this will be understandable.

The main opponent of such measurements is temperature, but even here the authors found all the necessary tools to take it into account and value it influence as for changes in the properties of the material under study, so and on the accuracy of the measurement process.

Thus, only the question-recommendation remained, whether two parametric graphs are needed in Fig. 1-12, or only a controlled parameter is enough - strain.

Author Response

The presented article discusses the results of a well-staged experiment on the study of in-situ instrumentation from manufacturing to loading of a Henequen fiber woven - bioepoxy composite.

 

The introduction quite fully reflects the methods and means of testing the materials under consideration using fiber Bragg gratings. The setting of the experiment and the measurement methods are set very scrupulously and clearly. Each result obtained is discussed in detail, all the features of the research are given and discussed. The conclusion fully reflects the subject of the article and the significance of the results obtained. The use of a high-tech interrogator removes all questions about the given graphical dependencies.

 

However, taking into account the well-known relationship between the wavelength and strain, which do not go beyond the limit values, I ask the authors to evaluate whether it is really necessary to give two graphs for both the wavelength and the strain. Solving this issue is my recommendation. If the authors want to leave the graphs unchanged, for example, to demonstrate the possibilities of the method, namely, for chemists, then this will be understandable.

 

The main opponent of such measurements is temperature, but even here the authors found all the necessary tools to take it into account and value its influence as for changes in the properties of the material under study, so and on the accuracy of the measurement process.

 

Thus, only the question-recommendation remained, whether two parametric graphs are needed in Fig. 1-12, or only a controlled parameter is enough - strain.

 

1. Thanks for your kind suggestion. We think is better for the readers to see the wavelength variation because mechanical and thermal strain are coupled. If anyone wants to repeat our experiment, and add a thermocouple, they can decouple the temperature and pressure.

 

 

Round 2

Reviewer 3 Report

I am happy with the revision