Conceptual Design of Compliant Structures for Morphing Wingtips Using Single-Row Corrugated Panels

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors!

The problem discussed in the article is extremely relevant; it has been the subject of research by aviation specialists for more than 20 years, but has not yet been solved. There are a number of comments regarding the text of the article.

 

Line 12:”  and parameter analysis is performed to investigate the effects of design parameters.” The meaning is unclear. What parameters were analyzed and the effect of which design parameters was studied

Lines 15-16: “The results demonstrate that the asymmetric stiffness corrugated panels have the capability to improve the shape-changing capability”. Bad expression

Lines 29-30: “… the aerodynamic shape of the wing can be adaptively changed to improve flight performance and…”.

Line31: “…morphing wingtips can also reduce the ground space, and have…”. the ground space for takeoff and landing??

Lines 37,38: “…and fiberglass to achieve wingtips deformation [7].”; “…actuators to achieve wingtips deformation [8].” Unwanted repeat

Lines 42-43: “Sun Jian et al. introduced honeycomb structures with negative Poisson's ratio as the filling structure [11].” Honeycomb filling is widely used in aircraft structures. How does this relate to the problems of the article?

Line 70: “In this paper, a conceptual level study is performed to verify the feasibility.” feasibility of what?

Line 74: “…and a parameter analysis explores the effect of different parameters of corrugated panels”. What is the effect of different parameters of corrugated panels on? Incomprehensible expression

Line 76: “…under the actuation displacement.” actuated? Unclear

Lines 82-84: “The compliant morphing wingtips based on unsymmetrical stiffness is shown in Figure 1. It is mainly composed of three parts: the main part of the wing, the fixed wingtip and the compliant morphing wingtip.” morphing wingtip= the main part of the wing U the fixed wingtip U compliant morphing wingtip? Consequently, morphing wingtip = morphing wingtip

Lines 117-119: “According to the asymmetric stiffness corrugated panels shown in Figure 2, a parametric model of the asymmetric stiffness corrugated panels is established to …” Duplicate!

 

Many such comments can be made about the text, but this does not seem to be the main drawback of the article’s material. Unfortunately, the article does not contain the schemes of the numerical and full-scale experiment with the panel. Such the schemes should indicate all the dimensions mentioned in the text both in the undeformed state of the panel and as a result of the action of forces on the part of the actuator. It is also necessary to clearly indicate the scheme for applying forces on the part by the actuator, as well as indicate its capabilities (able of creating forces of compression and/or tension, as well as possible displacement). If wing tip deflection is required in both directions, a force-deflection or force-deflection angle dependences must be provided explaining how each quantity described is measured or calculated. Without such a clear definition of all the properties of the structure, the characteristics of the actuator parameters and the response of the system to the forces applied to it, the meaning of optimization is unclear. In addition, the introduction states that controlled wingtip deflections must resist external aerodynamic influences. This is a natural requirement for active structures. But the text of the article says nothing about either modeling or experiment simulating such a situation.

The conclusions in the article are not specific, and most of them lack supporting results.

In addition to the studies of the properties of active aircraft structures presented in the article, there are a large number of other, very important ones. These are effective frequency range, structural damping of active structures and much more. Unfortunately, the state of the reviewed part shows that the authors are not familiar with the classic works in this area.

However, every new research in the field under consideration is useful for its progress.

Comments on the Quality of English Language

The article contains many incorrectly formulated expressions that violate the meaning of what is written. Too many repetitions. There are simple grammatical errors.

Author Response

Authors’ Response to the Reviews of aerospace-3106781, “Conceptual design of compliant structures for morphing wingtips using single-row corrugated panels”.

Many thanks for the comments and questions from the reviewers, which have significantly improved the manuscript. Below are the detailed replies to the reviewers. The modifications are summarised in this response and highlighted in red in the revised manuscript.

Author response to Reviewer: 1

Many thanks for the comments. The authors' replies are given below. The changes made in the manuscript are in red.

1) Line 12:”  and parameter analysis is performed to investigate the effects of design parameters.” The meaning is unclear. What parameters were analyzed and the effect of which design parameters was studied

Thanks for your suggestion. In this paper, we established a corrugated panel structure model based on asymmetric stiffness to explore the effect of asymmetric stiffness on the folding angle of the corrugated panel structure. We conducted a parameter analysis to investigate the impact of the thickness difference between the upper and lower parts of the corrugated panel structure, as well as the difference in the thickness of the individual units, on the folding angle.

The following sentences are now included in the lines 15-18 of revised manuscript as:

“A finite element model of the single-row corrugated panels is established, and parameter analysis is performed to investigate the impact of the thickness difference between the upper and lower parts of the corrugated panel structure, as well as the difference in the thickness of the individual units, on the folding angle.”

2) Lines 15-16: “The results demonstrate that the asymmetric stiffness corrugated panels have the capability to improve the shape-changing capability”. Bad expression

 

Thanks for your suggestion. We have updated the text, and the text change section has been marked with red font in lines 20-22.

“The results demonstrate that the asymmetric stiffness corrugated panels have the capability to increase the wingtips folding angle”.

 

 

3) Lines 29-30: “… the aerodynamic shape of the wing can be adaptively changed to improve flight performance and…”.

 

Sorry for causing any misunderstanding due to typo errors, which should be “changed”. We have updated the text, and the text change section has been marked with red font in lines 36-37.

“By folding the wingtips, the aerodynamic shape of the wing can be adaptively change to improve flight performance and reduce fuel consumption.”

4) Line31: “…morphing wingtips can also reduce the ground space, and have…”. the ground space for takeoff and landing??

 

Sorry for causing any confusion, which should be “Morphing wingtips on the tarmac helps save ground space for takeoff and landing.” We have updated the text, and the text change section has been marked with red font in lines 37-39.

5) Lines 37,38: “…and fiberglass to achieve wingtips deformation [7].”; “…actuators to achieve wingtips deformation [8].” Unwanted repeat

 

Thanks for your suggestion. We have updated the text, and the text change section has been marked with red font in lines 43-44.

“Shape memory alloy wire and spring are used as actuators to achieve wingtips folding [7-8]”

 

6) Lines 42-43: “Sun Jian et al. introduced honeycomb structures with negative Poisson's ratio as the filling structure [11].” Honeycomb filling is widely used in aircraft structures. How does this relate to the problems of the article?

 

Thanks for your suggestion. In this paper, we used honeycomb structures for the design of the leading and trailing edges of the flexible folding wingtip to maintain the overall aerodynamic shape of the structure, hence the mention of honeycomb structures.

 

7) Line 70: “In this paper, a conceptual level study is performed to verify the feasibility.” feasibility of what?

 

Sorry for causing any confusion. We have updated the text, and the text change section has been marked with red font in lines 76-77.

“In this paper, a conceptual level study is performed to verify the feasibility of asymmetric stiffness in increasing the folding angle of the corrugated panels.”

 

8) Line 74: “…and a parameter analysis explores the effect of different parameters of corrugated panels”. What is the effect of different parameters of corrugated panels on? Incomprehensible expression

 

Sorry for causing any confusion. We have updated the text, and the text change section has been marked with red font in lines 80-82.

“Secondly, a parametric model of this structure is established, and a parameter analysis explores the effect of different parameters of corrugated panels on the folding angle. “

 

9) Line 76: “…under the actuation displacement.” actuated? Unclear

 

Sorry for causing any misunderstanding. We have updated the text, and the text change section has been marked with red font in lines 82-84.

“Then, using Von Mises stress and strain as constraints, the corrugated panels are optimised with a genetic algorithm when the actuator works to achieve the maximum folding angle.”

 

10) Lines 82-84: “The compliant morphing wingtips based on unsymmetrical stiffness is shown in Figure 1. It is mainly composed of three parts: the main part of the wing, the fixed wingtip and the compliant morphing wingtip.” morphing wingtip= the main part of the wing U the fixed wingtip U compliant morphing wingtip? Consequently, morphing wingtip = morphing wingtip

 

Sorry for causing any confusion. We have updated the text, and the text change section has been marked with red font in lines 90-93.

“The wing including the compliant morphing wingtips based on unsymmetric stiffness is shown i n Figure 1(a). It is mainly composed of three parts: the inboard section of the wing, the extended outboard section and the compliant morphing wingtip. The compliant morphing wingtip includes the leading and trailing edges as well as the corrugated panel structure.”

 

 

11) Lines 117-119: “According to the asymmetric stiffness corrugated panels shown in Figure 2, a parametric model of the asymmetric stiffness corrugated panels is established to …” Duplicate!

 

 Thanks for your suggestions. We have updated the text, and the text change section has been marked with red font in lines 134-137.

“According to the structure shown in Figure 2, a parametric model of the asymmetric stiffness corrugated panels is established to conduct parameter analysis so that the effect of the two ways mentioned above on the shape-changing capability of corrugated panels is verified.”

 

 

12) Many such comments can be made about the text, but this does not seem to be the main drawback of the article’s material. Unfortunately, the article does not contain the schemes of the numerical and full-scale experiment with the panel. Such the schemes should indicate all the dimensions mentioned in the text both in the undeformed state of the panel and as a result of the action of forces on the part of the actuator. It is also necessary to clearly indicate the scheme for applying forces on the part by the actuator, as well as indicate its capabilities (able of creating forces of compression and/or tension, as well as possible displacement). If wing tip deflection is required in both directions, a force-deflection or force-deflection angle dependences must be provided explaining how each quantity described is measured or calculated. Without such a clear definition of all the properties of the structure, the characteristics of the actuator parameters and the response of the system to the forces applied to it, the meaning of optimization is unclear. In addition, the introduction states that controlled wingtip deflections must resist external aerodynamic influences. This is a natural requirement for active structures. But the text of the article says nothing about either modeling or experiment simulating such a situation.

The conclusions in the article are not specific, and most of them lack supporting results.

In addition to the studies of the properties of active aircraft structures presented in the article, there are a large number of other, very important ones. These are effective frequency range, structural damping of active structures and much more. Unfortunately, the state of the reviewed part shows that the authors are not familiar with the classic works in this area.

However, every new research in the field under consideration is useful for its progress.

 

Thank you for your suggestions. In this paper, we propose a flexible folding wingtip structure based on asymmetrical stiffness, where the asymmetrical stiffness is primarily controlled by adjusting the upper and lower thicknesses of the corrugated panel structure as well as the thicknesses between the units. Therefore, the focus of this study is to explore the feasibility of these two stiffness tailoring methods in enhancing the folding angle performance of the corrugated panel structure. Consequently, we did not perform simulations and experimental analyses on a full-scale model.

Regarding the choice of actuator in this study, we used the Actuonix Motion Devices linear actuator P16-100-256-12-P. The actuator has a maximum driving force of 300N and a maximum displacement of 100mm. The flexible folding wingtip structure designed in this paper is only intended for upward deflection.

For the measurement of the folding angle, we used motion capture to capture the deformation of the point marked with a red circle in Figure 8, and then calculated the angle between the central axes of the structure before and after deformation.

In this paper, the main focus is on the impact of asymmetric stiffness corrugated panel structures on the deformation capability of flexible folding wingtips. Therefore, we did not consider the load-bearing capacity of the structure under aerodynamic loads and effective frequency range, structural damping of active structures. This aspect will be studied in detail in future research.

We have updated the text, and the text change section has been marked with red font in lines  106-107、lines112-116、 lines 140-142、lines 275-278、lines 310-313 and lines 315-318.

“As shown in the Figure 1(b), the folding angle is the angle between the connecting lines of the endpoints of the central axis before and after deformation.”

“Based on the previous research, this paper establishes a single-row corrugated panel structure based on asymmetric stiffness within the compliant morphing wingtip as shown in Figure 1 （the blue structure in the Figure 1）.Optimisation analysis is conducted on the corrugated panel structure to obtain the maximum folding angle, providing a basis for the full-scale model design in the future research.”

“In this paper, the main research is to verify the effect of the single-row corrugated panels based on the asymmetric stiffness on shape-changing capability without the flexible honeycomb structures in the leading and trailing edge.”

“The stroke of the actuator is 100mm, and the maximum actuation can be as large as 300N with the gear ratio 256:1. The actuator is controlled by its affiliated software and the extension of the actuator is given as a feedback signal.”

“Experimental results indicate that the folding angle of the asymmetric stiffness corrugated panel structure is increased by 55% compared with symmetric stiffness, demonstrating its potential in the design of compliant morphing wingtip structures.”

“Besides, the focus of this study is to explore the feasibility of two stiffness tailoring methods in enhancing the folding angle performance of the corrugated panel structure without considering the capability to carry aerodynamic loads, and the entire wingtip structure can be established for the simulation analysis and experimental work.”

 

13)The article contains many incorrectly formulated expressions that violate the meaning of what is written. Too many repetitions. There are simple grammatical errors.

Thank you for your valuable and thoughtful comments. We have carefully checked and improved the English writing in the revised manuscript. The changes made in the manuscript are in red.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

see attached file

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Please revise some mistyping errors.

Author Response

Authors’ Response to the Reviews of aerospace-3106781, “Conceptual design of compliant structures for morphing wingtips using single-row corrugated panels”.

Many thanks for the comments and questions from the reviewers, which have significantly improved the manuscript. Below are the detailed replies to the reviewers. The modifications are summarised in this response and highlighted in red in the revised manuscript.

Author response to Reviewer: 1

Many thanks for the comments. The authors' replies are given below. The changes made in the manuscript are in red.

1) Figure 1 is the only place to show the wing properties. In this figure it is impossible to figure out how the folding wing tip occurs, which is the folding angle, where the corrugated panel are located or what is the relation between the corrugated panels and the leading and trailing edges honeycomb structures. Therefore, I consider that a more precise explanation and more figures should be added to this section so it is possible to follow the research work presented.

 

Many thanks for suggesting the accuracy of the description. The revisions have been made from the comments. The following sentences are now included in the lines 95-97、lines 99-100、lines 104-110 、lines 112-116 and lines140-142 of revised manuscript as:

 

“In this demonstration model, the electrical linear actuator is used. The actuator is pinned at both ends so that it can rotate with the structure. To install the actuator and avoid interference, the middle part of the corrugated panel structure is removed.

 

“The corrugated panel structure is integrated with the leading and trailing edge honeycomb structures and can be manufactured using 3D printing.”

 

“Moreover, introducing asymmetric stiffness in the corrugated panels can facilitate the folding of the wingtips. As shown in the Figure 1(b), the folding angle is the angle between the connecting lines of the endpoints of the central axis before and after deformation. When the actuator operates, the corrugated panel structure, with its excellent folding performance and asymmetric stiffness, will elastically deform, thereby achieving wingtip folding. Therefore, the asymmetric stiffness of the corrugated panel structure significantly impacts the overall folding performance of the wingtip.”

 

“Based on the previous research, this paper establishes a single-row corrugated panel structure based on asymmetric stiffness within the compliant morphing wingtip as shown in Figure 1 （the blue structure in the Figure 1）.Optimisation analysis is conducted on the corrugated panel structure to obtain the maximum folding angle, providing a basis for the full-scale model design in the future research.”

 

“In this paper, the main research is to verify the effect of the single-row corrugated panels based on the asymmetric stiffness on shape-changing capability without the flexible honeycomb structures in the leading and trailing edge.”

 

2) It is rather confusing if the objective was to increase the stiffness why along the paper is the folding angle, by the way never defined with respect to which line is this angle measured, the one computed. Do the authors try to demonstrate that a higher folding angle implies higher stiffness? If so, can they provide an equation to relate both parameters? If there is a relation between folding angle and stiffness please provide results to show how the asymmetry of the corrugated panels increase the stiffness of the wing.

 

We apologize for any confusion caused by the calculation of the folding angle. The specific folding angle refers to the angle between the central axis of the upper and lower corrugated panel structures before and after deformation, as shown in Figure 4(c). In this paper, the optimisation objective is to alter the stiffness differences within the corrugated panel structure by changing the thickness of the upper and lower parts of the corrugated panels as well as the thickness between individual units, thereby achieving a larger folding angle of the corrugated panels. From the parameter analysis results in Section 3.2, it is evident that increasing the stiffness differences between the upper and lower parts of the corrugated panel structure, as well as between the units, can effectively enhance the folding angle of the corrugated panels. Therefore, for this corrugated panel structure, stiffness differences are the primary factor in increasing the folding angle. Furthermore, the experimental results in Section 5.2 indicate that, for a given actuated displacement, the asymmetric stiffness corrugated panel structure exhibits a better folding angle compared to the symmetric stiffness corrugated panel.

The following sentences and figures are now included in the lines163-165 of revised manuscript as:

“The folding angle as shown in Figure 3(c) is the angle between the connecting lines of the endpoints of the central axis before and after deformation.”

 

 

3) At Table 1 the density is expressed in t/mm3 units. Can the authors provide the meaning of “t” for these units?

Sorry for causing any misunderstanding due to typo errors, which should be “ton/mm³”. In this paper, the finite element analysis software used is Abaqus, with the modeling units selected in SI(mm). Therefore, the unit for density should be ton/mm³.

The modification appears on the Table 1 in the revised manuscript.

 

4) Please revise some mistyping errors.

Thank you for your valuable and thoughtful comments. We have carefully checked and improved the English writing in the revised manuscript. The changes made in the manuscript are in red.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Dear authors!

It should be acknowledged that the inaccuracies identified during the first review of the article have been corrected, but the number of remaining inaccuracies and errors in the text is unacceptably large. In addition, there are clearly unsuccessful expressions that distort the meaning of sentences and numerous repetitions. Only a small part of these inaccuracies is listed below. 

Lines 16-18. “… the thickness difference between the upper and lower parts of the corrugated panel structure, as well as the difference in the thickness of the individual units, on the folding angle.”

It is not advisable to use terms and definitions in the abstract that are disclosed only in the main text. Therefore, it is advisable to avoid the terms "upper and lower parts of the corrugated panel" in the abstract, possibly replacing them with the term "thickness characteristics of the panel"

 

Lines 85-87. The results demonstrate that introducing asymmetric stiffness can effectively enhance the shape-changing capability.

There are two comments on this sentence. The authors state: "...introducing asymmetric stiffness can effectively enhance the shape-changing capability." But it is not specified what shape-changing requirements the structure under study should meet. Although the introduction allowed us to clearly define these requirements. In order to successfully complete the sentence, it is desirable to add the name of the developed structure at the very end.

 

Lines 95-96. “In this demonstration model, the electrical linear actuator is used. The actuator is pinned at both ends so that it can rotate with the structure”. The term "rotate" is a misnomer here. The actuator bends with the wing.

 

Lines 96-97. “To install the actuator and avoid interference, the middle part of the corrugated panel structure is removed.”. Here, too, we would like to have answers to two questions. What kind of interference is this sentence talking about? If it is a harmful phenomenon, it should be described. If the middle part of the panel is removed, how can this panel withstand bending loads? Does this mean that only the actuator takes up bending stresses?

 

Lines 112-114. “…this paper establishes a single-row corrugated panel structure based on asymmetric stiffness within the compliant morphing wingtip as shown in Figure 1 （the blue structure in the Figure 1”

It follows from this sentence that the corrugated panel structure of the flexible wing tip is depicted in blue in Figure 1. But in Figure 1 itself, an arrow is visible pointing to the blue structure with the name - linear actuator. What does the blue structure depict?

 

Lines 128-129. “…the thickness of the upper and lower parts within each corrugation unit has a thickness ratio N; Second, there is a linear variation K in thickness between individual corrugation unit.(units?)” Please clearly formulate what N, K and unit are.

 

 

Lines 131-133. “In order to improve the shape-changing capability of the corrugated structure, the actuator is installed on the lower half of the central axis of the corrugated panel.” Please clarify what "shape-changing capability" means, as well as what the "lower half of the central axis of the  corrugated panel" is and where it is located in the structure.

In this state, the article is unsuitable for publication and requires significant revision.

Comments on the Quality of English Language

Extensive editing of English language required

Author Response

Authors’ Response to the Reviewers of aerospace-3106781, “Conceptual design of compliant structures for morphing wingtips using single-row corrugated panels”.

 

Many thanks for the comments and questions from the reviewers, which have significantly improved the manuscript. Below are the detailed replies to the reviewers. The modifications are summarised in this response and highlighted in red in the revised manuscript.

 

Author response to Reviewer:

 

Many thanks for the comments. The authors' replies are given below. The changes made in the manuscript are in red.

 

• Lines 16-18. “… the thickness difference between the upper and lower parts of the corrugated panel structure, as well as the difference in the thickness of the individual units, on the folding angle.”It is not advisable to use terms and definitions in the abstract that are disclosed only in the main text. Therefore, it is advisable to avoid the terms "upper and lower parts of the corrugated panel" in the abstract, possibly replacing them with the term "thickness characteristics of the panel"

 

Many thanks for suggesting the accuracy of the description. We have updated the text, and the text change section has been marked with red font in lines 15-17.

“A finite element model of the single-row corrugated panel is established, and parameter analysis is performed to investigate the impact of the thickness characteristics of the corrugated panel on the folding angle.”

 

• Lines 85-87. The results demonstrate that introducing asymmetric stiffness can effectively enhance the shape-changing capability. There are two comments on this sentence. The authors state: "...introducing asymmetric stiffness can effectively enhance the shape-changing capability." But it is not specified what shape-changing requirements the structure under study should meet. Although the introduction allowed us to clearly define these requirements. In order to successfully complete the sentence, it is desirable to add the name of the developed structure at the very end.

 

Thanks for your suggestions. We have updated the text, and the text change section has been marked with red font in lines 85-87.

“The results demonstrate that introducing asymmetric stiffness on the compliant morphing wingtip could effectively increase the folding angle.”

 

• Lines 95-96. “In this demonstration model, the electrical linear actuator is used. The actuator is pinned at both ends so that it can rotate with the structure”. The term "rotate" is a misnomer here. The actuator bends with the wing.

 

Many thanks for suggesting the accuracy of the description. We have updated the text, and the text change section has been marked with red font in lines 98-99.

“In this demonstration model, the electrical linear actuator is used. The actuator is pinned at both ends so that it can bend with the structure.”

 

• Lines 96-97. “To install the actuator and avoid interference, the middle part of the corrugated panel structure is removed.”. Here, too, we would like to have answers to two questions. What kind of interference is this sentence talking about? If it is a harmful phenomenon, it should be described. If the middle part of the panel is removed, how can this panel withstand bending loads? Does this mean that only the actuator takes up bending stresses?

 

Thanks for your suggestions. In this paper, in order to avoid interference between the actuator and the corrugated panel after the actuator is installed, the middle part is removed and the distance removed is 25mm, which is greater than the actuator thickness of 20mm. Since the removed region only accounts for part of the overall size, the overall folding capability can still be presented by the structure. The actuator will take up a small part of the external loads, but the majority of the loads will be carried by the structure. There should be a trade-off study between the shape-changing (having a increased folding angle) and load-carrying (carrying external loads) capabilities. The current study is focused on the potential of increasing the folding angle of the corrugated panel, and only the folding angle is investigated. In the future study, a more comprehensive study will be performed.

The following sentences are now included in the lines 99-102 of revised manuscript as:

“To install the actuator and avoid interference between the actuator and the corrugated panel, the middle part of the corrugated panel structure is removed. The width of panel removed is 25mm, which is larger than the actuator width of 20mm.”

 

• Lines 112-114. “…this paper establishes a single-row corrugated panel structure based on asymmetric stiffness within the compliant morphing wingtip as shown in Figure 1 （the blue structure in the Figure 1” It follows from this sentence that the corrugated panel structure of the flexible wing tip is depicted in blue in Figure 1. But in Figure 1 itself, an arrow is visible pointing to the blue structure with the name - linear actuator. What does the blue structure depict?

 

Sorry for causing any confusion. The blue area in Figure 1 is the single-row corrugated panel structure based on asymmetric stiffness, which does not include the internal actuator. Therefore, an additional arrow is used to label the internal “linear actuator”.

 

• Lines 128-129. “…the thickness of the upper and lower parts within each corrugation unit has a thickness ratio N; Second, there is a linear variation K in thickness between individual corrugation unit.(units?)” Please clearly formulate what N, K and unit are.

 

Many thanks for suggesting the accuracy of the description. Corrugated panel is a kind of periodic structure. The unit is a single corrugated panel unit, which can be repeated as shown in Figure 2. To better explain what "Unit" means, we annotate each unit in Figure 2.

As shown in Figure 2, N represents the ratio of the structural thickness of the lower part to the upper part in a corrugation unit. K represents the increase in thickness between two corrugation units.

 

 

 

• Lines 131-133. “In order to improve the shape-changing capability of the corrugated structure, the actuator is installed on the lower half of the central axis of the corrugated panel.” Please clarify what "shape-changing capability" means, as well as what the "lower half of the central axis of the corrugated panel" is and where it is located in the structure.

 

Sorry for causing any confusion. In fact, "shape-changing capability" means a larger folding angle. In order to increase the folding angle of the corrugated panel, the actuator is installed on the lower half of the central axis of the corrugated panel structure, and the offset distance is 10mm. We have updated the text, and the text change section has been marked with red font in lines 134-135.

“In order to increase the folding angle of the corrugated structure, the actuator is stalled 10 mm below the central axis of the corrugated panel.”

 

 

• Comments on the Quality of English Language：Extensive editing of English language required

 

Thank you for your valuable and thoughtful comments. We have carefully checked and improved the English writing in the revised manuscript. The changes made in the manuscript are in red.

The modification appears on the lines 142-144、lines 183-186、lines 197-200、lines 209-212、lines 244-248 、lines 276-286、lines 289-290、lines 294-295 、lines 296-298 and lines 300-303 in the revised manuscript.

 

Author Response File: Author Response.docx

Reviewer 2 Report

Comments and Suggestions for Authors

1.      Lines 93-95 authors claim “continuous transition of the wing can be achieved. Compared with traditional hinge morphing wingtips, this structure enjoys a better aerodynamic shape.” Can the authors provide results to support this statement?

2.      At Fig. 3 authors claim to show five corrugated units. It is not clear to this referee that at Fig 3 five corrugated units are shown. Coul the authors better explain this assertion?

3.      At lines 249 to 254 it is not clear if the 23.1º is referred to the asymmetric case and the 13.1º to the symmetric case. If it is so, then 43.3% certainly it is not the relation between one and the other case. Please expand and clear up this issue.

4.      At line 312 authors claim that asymmetric corrugated panels increased 55% the folding angle compared with the symmetric case. However, as pointed out at the previous item also at lines 249 to 254 authors claim that a 43,3% increase was obtained in this angle. Can please clarify this issue or did I misunderstand something in the reasoning?

 

Author Response

Authors’ Response to the Reviewers of aerospace-3106781, “Conceptual design of compliant structures for morphing wingtips using single-row corrugated panels”.

 

Many thanks for the comments and questions from the reviewers, which have significantly improved the manuscript. Below are the detailed replies to the reviewers. The modifications are summarised in this response and highlighted in red in the revised manuscript.

 

Author response to Reviewer:

 

Many thanks for the comments. The authors' replies are given below. The changes made in the manuscript are in red.

1. Lines 93-95 authors claim “continuous transition of the wing can be achieved. Compared with traditional hinge morphing wingtips, this structure enjoys a better aerodynamic shape.” Can the authors provide results to support this statement?

 

Thanks for your suggestions. For the hinged wingtip, because the morphing wingtip relies on the hinge to achieve the wingtip folding. A gap will be generated due to the hinge between the wing and the wingtip and morphing skin is needed to cover the gap. If not, the aerodynamic efficiency of the morphing wingtip could be affected.

The following sentences are now modified in the lines 93-98 of revised manuscript to improve the manuscript as:

“For the hinged wingtips, since wingtip relies on the hinge to achieve the wingtip folding, a gap could be generated if no morphing skin is adopted, which could affect the aerodynamic efficiency of the morphing wingtip. On the other hand, Continuous shape-changing could be achieved for the compliant wingtip, since the shape-changing is based on the structural deformation of the compliant structure, which is placed between the wing and the wingtip.”

 

 

2. At Fig. 3 authors claim to show five corrugated units. It is not clear to this referee that at Fig 3 five corrugated units are shown. Could the authors better explain this assertion?

 

Sorry for causing any confusion. In this paper, an asymmetric stiffness corrugated panel is established by stiffness tailoring, as shown in Figure 2. And the number of the units will be affected by the overall size of the structure. And thus, in Figure 2, there will be n units.

In Figure 3, five units considering the length of the actuator and the structure are used. Also, to install the actuator, the middle part of the corrugated panel is removed.

We have modified Figure 3 and marked five units in the revised manuscript.

 

3. At lines 249 to 254 it is not clear if the 23.1º is referred to the asymmetric case and the 13.1º to the symmetric case. If it is so, then 43.3% certainly it is not the relation between one and the other case. Please expand and clear up this issue.

 

Sorry for causing any misunderstanding.

The folding angle of corrugated panel with asymmetric stiffness after optimisation is 23.1°, and that of corrugated panel with the symmetric stiffness is 13.1°.

In the previous calculation, we divided the angle increment (23.1-13.1=10 degrees) to the folding angle after the optimisation, so the result is 43.3% (10/23.1). In fact, it should be divided by the folding angle of the symmetric stiffness corrugated panel, which could be regarded as the basis of the design, and then the increment is 76.3% (10/13.1).

We have updated the text, and the text change section has been marked with red font in lines 244-248 as:

“Before the optimisation, the folding angle is 13.1 °. After the optimisation with asymmetrical stiffness introduced, the folding angle is 23.1°. A  76.3％ increase can be obtained compared to the original design when other parameters remain unchanged, which shows that the stiffness tailoring could increase the folding angle significantly.”

Also, Table 4 is updated to show the change of the folding angle before and after the optimisation

 

4. At line 312 authors claim that asymmetric corrugated panels increased 55% the folding angle compared with the symmetric case. However, as pointed out at the previous item also at lines 249 to 254 authors claim that a 43,3% increase was obtained in this angle. Can please clarify this issue or did I misunderstand something in the reasoning?

 

Sorry for causing any confusion.

These are two different calculations. Line 312 is from the experimental work, and Line 278 to 288 are from the numerical work. Both the comparisons are made to those before the optimisation.

We have updated the sentences and added a Table 5  showing the experimental results after Figure 9 as

“Table 5 summarises the experimental results and numerical results. Some errors remain between the experimental results and the simulation results, which could be mainly caused by the differences of the material properties used in the numerical simulation. However, both simulation and experimental results show that the introduction of asymmetric stiffness can increase the folding angle of corrugated panel.

The experimental results show that before the optimisation, the folding angle is 9.9°when the actuation displacement is set as 30mm. After the optimisation, the folding angle becomes 22.1°. The increase of the folding angle is divided by that of the symmetric stiffness corrugated panel, which leads to the increment of 123.2%, and verifies that the asymmetric stiffness could increase the folding angle significantly. ”

Author Response File: Author Response.docx

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