Effects of Hybridization on Tensile, Flexural, and Damage Behaviors of Flax/Carbon Epoxy Composites
Round 1
Reviewer 1 Report
The authors have performed an interesting study on the hybridization of unidirectional composites made reinforced with flax and carbon fibers. The use of Acoustic Emission registration provides for interesting insight about damage behavior of hybrid natural fibers/ carbon fiber composites. Below are some minor comments:
- Figure 1: there is a mistake in the legend. The figure shows that 100% flax fibers have the highest strength and stiffness which is not in line with the text. The authors should correct this.
- Page 7 line 197: please provide a reference for the amplitude range and their relation with interface damage.
- Authors should clarify why the increase of hybridization rate results in increase in fiber breakage, although delamination damage mode should is more expected.
- The authors should add a few lines outlining if they think there would be an effect for stacking sequence and whether this can be explored in future studies.
Author Response
Point 1: Figure 1: there is a mistake in the legend. The figure shows that 100% flax fibers have the highest strength and stiffness which is not in line with the text. The authors should correct this.
Point 2: Page 7 line 197: please provide a reference for the amplitude range and their relation with interface damage.
Point 3: Authors should clarify why the increase of hybridization rate results in increase in fiber breakage, although delamination damage mode should is more expected.
Point 4: The authors should add a few lines outlining if they think there would be an effect for stacking sequence and whether this can be explored in future studies.
Response to Reviewer 1 Comments
Thank you for taking the time to review our manuscript and for your positive feedback. We are pleased to hear that you found our research on the hybridization of unidirectional composites made reinforced with flax and carbon fibers and acoustic emission to locate and classify damage to be of scientific and practical interest.
We appreciate your recommendation for publication. Thank you again for your valuable feedback.
Response to point 1: We appreciate your keen observation regarding the inconsistency between Figure 1's legend and the corresponding text. We have now amended the figure legend to accurately represent the data, ensuring it aligns with the textual description. The figure now correctly shows the strength of each material. We apologize for any confusion the initial error may have caused.
Response to point 2: Thank you for your suggestion to provide a reference for the amplitude range and its relation with interface damage. We agree that this will improve the understanding of our methodology. We have now included relevant references to support this relationship. These are established studies that demonstrate the correlation between amplitude range and interface damage in similar materials. We hope this addition will clarify our approach.
Response to Point 3: Thank you for your insightful question regarding the correlation between the hybridization rate and fiber breakage. Indeed, the observation that an increase in hybridization rate leads to more fiber breakage rather than delamination, which is often more expected, may initially seem counterintuitive. Our observation is due to the change in stress distribution within the composite as the hybridization rate increases. As hybridization becomes more prevalent, stress is transferred more efficiently across the interfaces, resulting in higher loads on the fibers themselves. This increased load can, in turn, lead to more fiber breakage. We recognize that this connection might not have been clear in the conclusion. However, we have provided a detailed discussion of this phenomenon in earlier sections, considering the specific characteristics of our material system.
Response to point 4: Thank you for highlighting the importance of considering the potential impact of stacking sequence on our results. We concur that the stacking sequence is a significant determinant of the mechanical properties and failure modes in composite materials and should not be disregarded. While our study was concentrated on a specific stacking sequence, we acknowledge the potential for diverse outcomes with alternative sequences. As such, future research endeavors could benefit from exploring the effects of varying stacking sequences, potentially leading to further optimization of composite performance.
We have incorporated this perspective into our manuscript, specifically within the conclusion section from lines 428 to 437, to underscore this potential area for future exploration. Your constructive feedback is instrumental in refining our manuscript and highlighting future research directions.
Thank you for your constructive feedback that has helped improve our manuscript.
Reviewer 2 Report
The paper experimentally investigated lax/carbon hybrid composite behaviors. It is a good work. The paper can be suggested after the revision.
-Please add a notation list.
- In order to provide a more comprehensive literature review, the authors should cite and discuss the following relevant paper in lines 27-29:
Stress concentration factors in tubular T/Y-joints strengthened with FRP subjected to compressive load in offshore structures. International Journal of Fatigue, 140, 2020;p.105719.
Stress concentration factors in tubular X-connections retrofitted with FRP under compressive load. Ocean Engineering, 229, 2021;p.108562.
- Please explain about the debonding between the layers.
-Fig. 9 needs more discussion in the text.
- In lines 60 and 61, “Flax fibers are characterized by Young's modulus of 72.9 GPa and strength of 742 MPa” Why is just this one Young's modulus value used? The composites have different Young's modulus. How it can be used in industry, when just one type is investigated.
Author Response
Point 1: Please add a notation list.
Point 2: in order to provide a more comprehensive literature review, the authors should cite and discuss the following relevant paper in lines 27-29 :
Stress concentration factors in tubular T/Y-joints strengthened with FRP subjected to compressive load in offshore structures. International Journal of Fatigue, 140, 2020;p.105719.
Stress concentration factors in tubular X-connections retrofitted with FRP under compressive load. Ocean Engineering, 229, 2021;p.108562.
Point 3: Please explain about the debonding between the layers.
Point 4: Fig. 9 needs more discussion in the text.
Point 5: In lines 60 and 61, “Flax fibers are characterized by Young's modulus of 72.9 GPa and strength of 742 MPa” Why is just this one Young's modulus value used? The composites have different Young's modulus. How it can be used in industry, when just one type is investigated.
Response to Reviewer 2 Comments
Thank you for reviewing our manuscript and for your valuable feedback. We appreciate your positive comments and your suggestions for improvement. We will address each of your points below.
Response to point 1: Thank you for your suggestion to include a notation list. We understand that this can enhance readability and quick reference. However, the journal's guidelines do not typically require the inclusion of a notation list. Our aim was to maintain adherence to the journal's formatting requirements while ensuring that all notations were clearly defined within the text at their first occurrence. If you believe that a notation list would significantly improve the manuscript's clarity, we are open to adding one despite the journal's guidelines. Please let us know if you strongly recommend this addition.
Response to point 2: Point 2: We appreciate your suggestion to include the mentioned references to provide a more comprehensive literature review. These papers indeed contribute significantly to the current understanding of stress concentration factors in tubular connections in the context of offshore structures, and it would be beneficial to discuss them in our manuscript.
We have now revised lines 27-29 of our manuscript to incorporate these relevant studies.
Response to point 3: Point 3: Thank you for bringing up the topic of debonding between the layers. Debonding indeed refers to the loss of adhesion between the fiber and the matrix within a layer, while delamination refers to the separation between different layers of a composite material. In our study, both debonding and delamination were carefully considered and discussed.
Our manuscript outlines the effects of both debonding and delamination on the mechanical properties of our composite material. If you would like a more detailed explanation of these aspects, we will revise the manuscript to provide a more thorough discussion of debonding and delamination, including their implications for our study and the field at large. We appreciate your feedback, as it assists us in enhancing the comprehensiveness and clarity of our work.
Response to point 4: We appreciate your remark concerning Figure 9. Within our manuscript, we have already presented an in-depth analysis of the observations derived from Figures 3 (c) and (d), as well as Figures 8 (c) and (d) in their corresponding sections. As a result, the discussion associated with Figure 9, which primarily reinforces and corroborates the conclusions from the preceding figures, may seem less extensive in comparison.
However, to address your feedback, we have ensured that the relationship and correlation between these figures and their findings are emphasized within the manuscript..
Response to point 5: Thank you for your inquiry about the Young's modulus value stated in lines 60 and 61. The given value of 72.9 GPa represents the modulus of the specific flax fibers used in our study, as provided by our supplier. We acknowledge that there can be variability in these values for different types of flax fibers, but the fibers we use consistently in our work have this specified modulus.
Our focus on this particular type of flax fiber is based on its consistent performance in our research over the years. Despite this, we agree with your point about the diversity of composite materials and their respective properties. Each composite's Young's modulus can vary depending on multiple factors, including the specific properties of its constituent materials.
Reviewer 3 Report
1. Figure 1 is not clear; the quality can be improved as well as author is advised to cross check whether strain is in %. It is advised to use dot (.) rather than comma (,) to put decimal point.
2. Line 96 it is said that F16 shows non-linear elastic behavior, which is not visible in the Figure 1, it seems linear.
3. Please correct the line 104 (“This brittle fracture is due to lower strain to the failure of carbon fibers, conducting a typical catastrophic explosive fracture of the hybrid composite.”). It is advised to avoid the term “explosive fracture”, or if, author intends to use it, please justify it’s meaning.
4. Please explain Figure 2 in detail.
5. Improvement in quality of Figure 4 and table 4 is required.
6. Authors should talk more about AE technique and other damage evaluations tools in the introduction. And conclusion should discuss quantitative data for comparison.
Author Response
Reviewer 3
Comments and Suggestions for Authors
In this paper, a combination of digital image correlation (DIC) and acoustic emission (AE) was used to locate and classify the type of damage depending on the stacking sequence of the laminate during flexural loading. It can be accepted after revision.
Point 1: Figure 1 is not clear; the quality can be improved as well as author is advised to cross check whether strain is in %. It is advised to use dot (.) rather than comma (,) to put decimal point.
Point 2: Line 96 it is said that F16 shows non-linear elastic behavior, which is not visible in the Figure 1, it seems linear.
Point 3: Please correct the line 104 (“This brittle fracture is due to lower strain to the failure of carbon fibers, conducting a typical catastrophic explosive fracture of the hybrid composite.”). It is advised to avoid the term “explosive fracture”, or if, author intends to use it, please justify it’s meaning.
Point 4: Please explain Figure 2 in detail.
Point 5: Improvement in quality of Figure 4 and table 4 is required.
Point 6: Authors should talk more about AE technique and other damage evaluations tools in the introduction. And conclusion should discuss quantitative data for comparison.
Response to Reviewer 3 Comments
Thank you for reviewing our manuscript and for your valuable feedback. We appreciate your positive comments and your suggestions for improvement. We will address each of your points below.
Response to point 1: We appreciate your feedback regarding Figure 1. We understand the importance of clear, high-quality figures for conveying our results effectively. We will take steps to improve the quality of this figure, ensuring the readability and clarity of all elements.
In terms of the strain measurement, we assure you that it is indeed expressed in percentage. We apologize if this was not made clear and will make the necessary adjustments for accuracy.
Regarding your suggestion to use a dot (.) instead of a comma (,) for decimal points, we acknowledge that this is the standard practice in scientific writing, particularly for international audiences. We would also like to inform you that the figures were generated using Originpro software. However, we are currently experiencing difficulties in modifying the decimal point format within the software. Rest assured, we will ensure that this change is implemented in the final revised version of the manuscript. Furthermore, we anticipate that the journal's review process will also require us to adhere to this modification.
Response to point 2: We appreciate your observation regarding the non-linearity in the curve. Indeed, this behavior is typical for flax fibers and can be attributed to their unique mechanical properties.
Flax fibers often exhibit non-linear behavior due to specific characteristics inherent to natural fibers. This non-linear behavior is typically observed close to the test beginning, at a strain level of less than 0.25%.
To provide a more comprehensive understanding of this behavior, we highly recommend referring to our previous research works, which extensively discuss the mechanical properties and behavior of flax fiber composites. The following articles are particularly relevant in this context:
"Combining short flax fiber mats and unidirectional flax yarns for composite applications: effect of short flax fibers on biaxial mechanical properties and damage behavior"
"Replacing stitching and weaving in natural fiber reinforcement manufacturing, part 1: mechanical behavior of unidirectional flax fiber composites"
"Replacing stitching and weaving in natural fiber reinforcement manufacturing, part 2: Mechanical behavior of flax fiber composite laminates"
These articles provide comprehensive discussions on the non-linearities observed in flax fiber composites, along with detailed insights into their underlying mechanisms. Reviewing these works will undoubtedly enhance the understanding of the observed non-linear behavior.
Response to point 3: Thank you for your comment regarding the terminology used in line 104 of the manuscript. We apologize for any confusion caused by the phrase "explosive fracture" and understand your concern about its usage. We have updated the sentence as follows:
"This brittle fracture is attributed to the lower strain-to-failure of carbon fibers, resulting in a typical catastrophic fracture with abrupt failure of the hybrid composite.".
Response to point 4: Thank you for pointing out that a more detailed discussion has been added between lines 100 and 115 of the manuscript.
Response to point 5: Thank you for your feedback regarding Figure 4 and Table 4. We understand the importance of ensuring high-quality figures and tables that effectively convey the relevant information to readers.
Figure 4 presents the determination of the best cluster number based on the Davies-Bouldin index for both tensile (a) and flexural (b) testing of the different composites. We believe that these figures provide clear visual representations of the clustering analysis results, aiding in the understanding of the optimal cluster numbers for the tested composites.
However, we appreciate any specific suggestions or recommendations you may have for improving the quality or clarity of these figures. If there are any specific modifications you would like us to consider, please kindly provide us with the details, and we will promptly address them to enhance the figures accordingly.
Response to point 6: Thank you for your suggestion to provide more information about the Acoustic Emission (AE) technique and other damage evaluation tools in the introduction. We acknowledge the importance of discussing these techniques as they contribute to a comprehensive understanding of composite material behavior.
While the AE technique is a well-known method for monitoring and evaluating damage in materials, including composites, we would like to clarify that the emphasis of our article is primarily on the analysis of the results related to the carbon/linen hybridization. As such, the focus of the manuscript is to investigate the effects of hybridization on the mechanical properties and failure modes of the composite.
Regarding the conclusion, we appreciate your suggestion to include quantitative data for comparison. We have revised and enhanced the conclusion by providing a quantitative summary of the obtained results, enabling a more thorough comparison and evaluation of the effects of hybridization on the composite's mechanical properties and failure modes.
Round 2
Reviewer 1 Report
Article can be published in the present form. No further corrections.
Reviewer 2 Report
ok
Reviewer 3 Report
I am satisfied with the answers, manuscript can be accepted.
