Increasing Deformation Energy Absorption of AM Drone Fuselages Using a Low-Density Polymeric Material

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript has certain engineering significance. Before considering publishing this manuscript, the following comments should be revised.

1. The background in the Abstract is too long, and the author should focus on elaborating on the content and results of their research, as well as the significance it brings.

2. The Introduction Section did not emphasize the necessity of the author's research.

3. What is the purpose of setting up Figure 1 (b)? There is no specific analysis.

4. Line 181-183: What is the specific comparative analysis based on the three models, how to obtain the final model, and the lack of comparison and analysis of figures and text (or tables). The simplification process of Line 193-200 also requires specific reasons to be explained.

5. The reviewer suggest not placing figures 4 (a) and (b).

6. The definition of the samples only appears in the figure, and the main text needs to list it in detail.

7. The content in Section 3 and Conclusions requires detailed quantitative analysis and conclusions.

8. The boundary conditions set in the paper do not seem to belong to the category of collisions. Explain the difference between the two and how they are related to collisions?

Author Response

Acknowledgments: The Authors express their sincere gratitude to the Reviewer for sharing his/her time and knowledge. They revised the manuscript, incorporating the Reviewer’s constructive comments; the yellow color highlights the modifications made to the text.

 

1) Comment. The background in the Abstract is too long, and the author should focus on elaborating on the content and results of their research, as well as the significance it brings.

Answer. The Authors appreciate this comment and shortened the Abstract, clarifying the research idea and primary contribution to the applied sciences.

Correction in the manuscript: The Abstract was rewritten entirely.

 

2) Comment. The Introduction Section did not emphasize the necessity of the author's research.

Answer. The Authors accepted this criticism and extended the literature review to identify the current gaps and motivate this research.

Correction in the manuscript: The new text (Lines 89-126 of the updated manuscript) clarifies the necessity of the LW-PLA research and development of its metastructures.

 

3) Comment. What is the purpose of setting up Figure 1 (b)? There is no specific analysis.

Answer. This comment is understandable. This figure illustrates the internal structure of the cylindrical samples used for the preliminary calibration of the FFF settings and mechanical characterization of the polymeric materials. The Authors have extended Section 2.1, substantiating the choice of the FFF settings and describing the sample fabrication and testing procedures.

Correction in the manuscript:

• Lines 167-171. This text describes the PLA fabrication settings and provides a choice for the printing bed temperature.
• Lines 174-187. This explanation clarifies the selection of the LW-PLA manufacturing parameters.
• Lines 201-213. This text clarifies the testing setup and procedures.

 

4) Comment. Line 181-183: What is the specific comparative analysis based on the three models, how to obtain the final model, and the lack of comparison and analysis of figures and text (or tables)? The simplification process of Lines 193-200 also requires specific reasons to be explained.

Answer. The Authors sincerely appreciate these thoughtful notes. The drone images are copyrighted objects. Additionally, these descriptions do not significantly impact the illustrative research content. Therefore, the Authors provided the minimal clarifications necessary to understand the issue. In particular, the Opterra 2M Wing stood out as the most suitable candidate for further investigation and material substitution due to the possibility of isolating the front part of the fuselage, which is already formed as a separate, prototyping-ready fragment. The specified drone characteristics are necessary to determine the theoretical collision energy. The corresponding comments were added.

Correction in the manuscript:

• Lines 238-240. This sentence clarifies the choice of the Opterra 2M Wing drone.
• Line 261. This reference establishes a connection between the specified drone parameters and the theoretical calculation as outlined in Equation 1.

 

5) & 6) Comments. The reviewer suggests not placing Figures 4(a) and 4(b). The definition of the samples only appears in the figure, and the main text needs to list it in detail.

Answer. The Authors understand the comment. However, they respectfully disagree with the recommended modification. These figures reveal the total view (identical for all the test specimens) and internal structure of the reference specimen. The latter view is essential for imagining and comparing the internal structure of the front parts of the drone fuselage, which are involved in this test campaign. At the same time, the Authors accept the criticism addressed to the specimens’ description. Therefore, they carefully revised the manuscript and provided the correct references to the sub-parts of Figure 4 in the text.

Corrections in the revised version:

• Lines 281-282. This sentence introduces Figure 4.
• Lines 283, 285, and 331. These references link the samples’ descriptions to the proper parts of Figure 4.
• Lines 294-295. This comment clarifies the notations of the test samples, linking them to Table 3.

 

7) Comment. The content in Section 3 and Conclusions requires detailed quantitative analysis and conclusions.

Answer. The illustrative nature of the study, combined with the limited number of test specimens, does not permit a quantitative analysis of the test outcomes. However, the Authors accepted the criticism related to the discussion and conclusion drawbacks. They carefully verified the text and rephrased the misleading formulations in Section 3 and entirely rewrote Section 4 (“Conclusions”).

Correction in the manuscript:

• Section 3 was verified, rephrasing misleading wordings—yellow color highlights all corrections in the text.
• Section 4 was entirely rewritten.

 

8) Comment. The boundary conditions set in the paper do not seem to belong to the category of collisions. Explain the difference between the two and how they are related to collisions.

Answer. The Authors acknowledge this essential comment. It is necessary to note that the 300 J collision energy employed in this study does not accurately represent a typical drone collision scenario. Instead, it serves as a theoretical boundary condition to standardize the comparison of deformation energy absorption across different prototype configurations. This simplification enables a consistent evaluation framework without requiring drop-weight or dynamic impact tests. The corresponding clarifications were added throughout the text.

Correction in the manuscript. The corresponding comments were added in Lines 25-24, 256-258, 403-407, 490-494, and 540 of the modified manuscript.

Reviewer 2 Report

Comments and Suggestions for Authors

1. The abstract lacks key findings from the research.
2. The motivation for the study is not clearly articulated in the abstract.
3. The introduction should reference research on 3D printing as well as studies related to the mechanical characterization of PLA and its variants utilized in this investigation.
4. Clarification is needed regarding the rationale for setting the bed temperature at 55°C, as well as the methodology for determining the speed used in the current study; including relevant references would aid reader comprehension.
5. The selection of PLA and LW-PLA warrants further justification; conducting a material index analysis or using a modified model would strengthen the rationale for material selection in the design.
6. The temperature range should be corrected in line 138.
7. Figure 1 should include a label for part c to enhance clarity for the readers.
8. The choice of square internal infill requires justification, as alternative infill structures may exhibit superior performance.
9. In Figure 2, the displacement for one of the samples of PLA and LW-PLA is notably less compared to the other samples; an explanation is needed.
10. In Equation 1, the omission of the material constant should be addressed.
11. Figure 4 should be labeled to facilitate better understanding for the readers.
12. The authors must clarify how the compression test results at specific parameters can be compared with the collision test value of 300 J.
13. The authors need to incorporate drop tests and compare the performance of the design structures accordingly.
14. The results and discussion section should be revised for clarity and accessibility for readers.
15. The conclusions should be definitive and well-supported by the findings.

Author Response

Acknowledgments: The Authors express their sincere gratitude to the Reviewer for sharing his/her knowledge, thoughtful suggestions, and raised questions, which substantially improved the presentation quality and identified problems for further research. The Authors revised the manuscript, incorporating the Reviewer’s constructive comments; the yellow color highlights the modifications made to the text.

 

1) & 2) Comments. The abstract lacks key findings from the research. The motivation for the study is not clearly articulated in the abstract.

Answer. The Authors appreciate this comment and shortened the Abstract, clarifying the research idea and primary contribution to the applied science.

Correction in the manuscript: The Abstract was rewritten entirely.

 

3) Comment. The introduction should reference research on 3D printing as well as studies related to the mechanical characterization of PLA and its variants utilized in this investigation.

Answer. The Authors accepted this criticism and extended the literature review to identify the current gaps and motivate this research.

Correction in the manuscript: The new text (Lines 89-110 of the updated manuscript) clarifies the necessity of the LW-PLA research and development of its metastructures.

 

4) Comment. Clarification is needed regarding the rationale for setting the bed temperature at 55°C, as well as the methodology for determining the speed used in the current study; including relevant references would aid reader comprehension.

Answer. The Authors appreciate this valuable note. They have extended Section 2.1, substantiating the choice of the FFF settings and describing the sample fabrication procedures.

Correction in the manuscript:

• Lines 167-171. This text describes the PLA fabrication settings and provides a choice for the printing bed temperature.
• Lines 174-187. This explanation clarifies the selection of the LW-PLA manufacturing parameters.

 

5) Comment. The selection of PLA and LW-PLA warrants further justification; conducting a material index analysis or using a modified model would strengthen the rationale for material selection in the design.

Answer: This study builds on the research program [12] that explored additive drone manufacturing using a basic desktop printer and commercially available polymer materials. The choice of PLA and LW-PLA in this work is also based on research [12], which thoroughly examined the mechanical and fabrication properties of various polymer filaments for use in UAVs. PLA was chosen for its non-toxicity, ease of processing, and affordability, while LW-PLA showed strong potential for lightweight applications. Šostakaitė et al. [12] summarized key material properties, including tensile strength, elastic modulus, and thermal characteristics. These results, along with their compatibility with desktop FFF printers, justify the selection of PLA for this study, which aims to improve deformation energy absorption in drone fuselage parts.

Correction in the manuscript. The corresponding clarification is presented in Lines 111-122 of the modified manuscript.

 

6) Comment. The temperature range should be corrected in line 138.

Answer: The specified temperature range is correct; however, it is related to the FFF nozzle parameters. This issue was unclear from the specification provided. Therefore, the Authors rephrased this comment.

Correction in the manuscript. The comment on Lines 160-161 was rephrased.

 

7) Comment. Figure 1 should include a label for part c to enhance clarity for the readers.

Corrections in the revised version: The suggested labels were added.

 

8) Comment. The choice of square internal infill requires justification, as alternative infill structures may exhibit superior performance.

Answer: This thoughtful comment is appreciated.

Corrections in the revised version: The corresponding clarification was added in Lines 141-147.

 

9) Comment. In Figure 2, the displacement for one of the PLA and LW-PLA samples is notably less compared to the other samples; an explanation is needed.

Corrections in the revised version: The corresponding clarification was added in Lines 201-213.

 

10) Comment. In Equation 1, the omission of the material constant should be addressed.

Answer: The error is acknowledged.

Corrections in the revised version: The equation has been corrected, and the corresponding description has been added in Line 262.

 

11) Comment. Figure 4 should be labeled to facilitate better understanding for the readers.

Answer: The Authors acknowledge the comment and recognize the critique regarding the specimen description. Consequently, they have carefully revised the manuscript and corrected the references to the sub-parts of Figure 4 within the text.

Corrections in the revised version:

• Lines 281-282. This sentence introduces Figure 4.
• Lines 283, 285, and 331. These references link the samples’ descriptions to the proper parts of Figure 4.
• Lines 294-295. This comment clarifies the notations of the test samples, linking them to Table 3.

 

12) & 13) Comment. The authors must clarify how the compression test results at specific parameters can be compared with the collision test value of 300 J. The authors need to incorporate drop tests and compare the performance of the design structures accordingly.

Answer: The Authors acknowledge this fundamental comment. It is essential to note that the 300 J collision energy employed in this study does not accurately represent a typical drone collision scenario. Instead, it serves as a theoretical boundary condition to standardize the comparison of deformation energy absorption across different prototype configurations. This simplification enables a consistent evaluation framework without requiring drop-weight or dynamic impact tests, which are beyond the scope of this study.

Corrections in the revised version: The corresponding comments were added in Lines 25-24, 256-258, 403-407, 490-494, and 540 of the modified manuscript.

 

14) Comment. The results and discussion section should be revised for clarity and accessibility for readers.

Answer: The Authors accepted this criticism. They carefully verified the text and rephrased the misleading formulations in Section 3.

Corrections in the revised version: Section 3 was verified, rephrasing misleading wordings—yellow color highlights all corrections in the text.

 

15) Comment. The conclusions should be definitive and well-supported by the findings.

Corrections in the revised version: Section 4 was entirely rewritten to reflect the key findings and the essential contribution of this study to applied sciences.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors The author has well addressed to the reviewer's comments. The manuscript could be accpeted before responsing the following issues: The load of real collision scenarios should be distinguished from the conditions in this manuscript, and attention should be paid to their differences, as well as potential reasons that can be used for the research in this article.

Author Response

Comment: The author has addressed the reviewer's comments. The manuscript could be accepted after addressing the following issues: The load of real collision scenarios should be distinguished from the conditions presented in this manuscript, and attention should be paid to their differences, as well as potential reasons that can be used for the research in this article.

Answer: The Authors understand and accept this criticism. The assumed deformation energy facilitates a comparison of the mechanical resistance of the tested prototypes shown in Figures 9b, 10, and 12. These test specimens exhibit distinct deformation resistance and cannot be compared without introducing a more or less realistic deformation limit. At the same time, neither the monotonic (Figure 9) nor the repeated (Figure 10) loads adequately reflect real collision scenarios. Therefore, future studies must utilize drop-weight or dynamic tests for more accurate comparisons. The corresponding comment has been added in Section 3.3. The authors also slightly modified Section 4 (“Conclusions”) to reflect the current limitations of the research. All corrections in the text are highlighted in yellow.

Corrections in the manuscript:

• Lines 493-496. This text highlights the research limitation concerning the failure of the conducted test to reflect the loads observed in real collision scenarios accurately.
• Lines 545-547. This revised conclusion highlights the limitations of the current mechanical tests.
• Lines 551-552. This new sentence highlights the necessity of advanced algorithms to achieve a multi-objective optimization solution.