Research on the Blow-Off Impulse Effect of a Composite Reinforced Panel Subjected to Lightning Strike
Round 1
Reviewer 1 Report
The paper "Research on blow-off impulse effect of composite reinforced panel subject to lightning strike" is interesting and within the scope of Applied Sciences. The content is coherent with recent development of the aircraft industry: the more composite materials are used, the more their structural performances should be investigated. Particularly, consequences of lightning strike could lead to serious damage and premature failure of structures.
The paper is well written and organized. However, I have some questions for the authors:
Table 1 and Table 2 are not clear: what are the values of the thickness column?
In table 3, the unit of measure of density is not correctly indicated;
Figure 1 could be improved;
I think that SOLID69 and SOLID164 refer to elements available in the software ANSYS. The authors should clarify both elements and declare and justify the software they used.
In Figure 5 the scale of representation lacks. The same for Figures 6 and 8;
Legends in figures 10 and 11 are not readable;
The conclusion section should be improved: why this study? are the obtained results useful for the sector? What are further developments?
Author Response
Response to Reviewer 1 Comments
Open Review (x) I would not like to sign my review report
( ) I would like to sign my review report
English language and style ( ) Extensive editing of English language and style required
( ) Moderate English changes required
(x) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style
Yes | Can be improved | Must be improved | Not applicable | |||
Does the introduction provide sufficient background and include all relevant references? | ( ) | (x) | ( ) | ( ) | ||
Is the research design appropriate? | (x) | ( ) | ( ) | ( ) | ||
Are the methods adequately described? | ( ) | (x) | ( ) | ( ) | ||
Are the results clearly presented? | ( ) | (x) | ( ) | ( ) | ||
Are the conclusions supported by the results? | ( ) | ( ) | (x) | ( ) | ||
Reviewer #1: Comments and Suggestions for AuthorsThe paper "Research on blow-off impulse effect of composite reinforced panel subject to lightning strike" is interesting and within the scope of Applied Sciences. The content is coherent with recent development of the aircraft industry: the more composite materials are used, the more their structural performances should be investigated. Particularly, consequences of lightning strike could lead to serious damage and premature failure of structures.
The paper is well written and organized. However, I have some questions for the authors:
Point 1: Table 1 and Table 2 are not clear: what are the values of the thickness column?Response 1: Because carbon fiber/epoxy composite materials can be regarded as transverse isotropic ones, the values of the thickness column are the same as those of transverse column. Therefore, we combine them into one column.
Point 2: In table 3, the unit of measure of density is not correctly indicated;Response 2: Relative revision has been made in our manuscript.
Point 3: Figure 1 could be improved;Response 3: Relative revision has been made in our manuscript.
Point 4: I think that SOLID69 and SOLID164 refer to elements available in the software ANSYS. The authors should clarify both elements and declare and justify the software they used.Response 4: Relative revision has been made in our manuscript.
Point 5: In Figure 5 the scale of representation lacks. The same for Figures 6 and 8;Response 5: Relative revision has been made in our manuscript.
Point 6: Legends in figures 10 and 11 are not readable;Response 6: Relative revision has been made in our manuscript.
Point 7: The conclusion section should be improved: why this study? are the obtained results useful for the sector? What are further developments?Response 7: Relative revision has been made in our manuscript.
Author Response File: 
Author Response.doc
Reviewer 2 Report
This paper presents a numerical analysis on the effect of lightening strike to composite reinforced panel.
The main topic is interesting, but the paper need major improvements in order to reach a the scientific level of an international publication.
However, the remarks below are provided in order to improve the paper: (Both editorial and technical comments are given in the order they appear in the text.)
- line 14-> Please change "Mises" into "von Mises"
- line 119-> Please change "temperature-dependent" into "temperature-dependence".
- line 121-> Please accurately define what is the considered composite material and report this definition also in the tables 1-3 captions.
- line 127, Section 2.2-> Please define the adopted software (I imagine that it is Ansys) and the mesh characteristics. I mean, what is the time step? And how did the authors select it? How many elements for each layer? How many degree of freedom per element etc. In addition please give information about the computational cost of the model.
- line 138, Figure 1-> Please introduce the geometrical dimensions also in this figure.
- line 175-> What is the meaning of "JWL" acronym?
- line 179-> What does 59# represent?
- line 183-185-> What is the adopted reference system? Please clarify it with reference to the fiber orientation.
- line 188, Figure 4-> What are the information exchanged between the two modules? Did the authors manually perform the exchange of information or is it automatic?
- line 191, Section 3-> Without a thorough model validation using experimental results (or other numerical models available in literature) it is difficult to assess the quality of the presented numerical results. This is one of the main weak point of the paper. I consider this point of paramount relevance for my judgement on the paper.
- line 201->Please report the temperature unit of measure in the legend or figure captions. The same point is valid for Figure 6 and 8.
- line 203-> Did the authors check the quality of this result (max temp= 83937.3 °C) comparing it with known result published in literature? Are the authors sure that this result is not biased by a poor mesh quality?
-line 208-> Please be consistent with the notation, please change "Fig.6 and Fig.7" into "Figure 6 and Figure 7".
- line 215-> I would like to know if the solid69 element is capable of accounting different fiber orientation for different layer? Please clarify how is built the model, there is one layer of element for each layer of fibers? Or there is another strategy? I imagine that the solid model can homogenize the behavior of multiple layers but how is possible that an homogenized model have different layer of stress or thermo-mechanical properties? Please clarify.
- line 257, Section 3.2-> Please give all the details of the numerical analysis: time step, element dimension, non linear solver etc. Then, is there any other load in addition to the blow-off? I mean, gravitational load.. etc.
- line 267-> Please change "Mises" into "von Mises"
- line 269-> Please clarify what is the collapse criterion. How are deleted the elements? Is the mesh modified at each time step?
- line 271-> Please change "Mises" into "von Mises"
- line 312-> Please use the same legend scale for each sub-figure in order to easily compare the results.
- line 336-> Please change "Mises" into "von Mises"
- What are the main advances in science produced by this paper? What are the novelty presented to the scientific community? I can see the use of a commercial software on a known problem, what is the original part?
- The overall grammar and sentence construction is very poor. Some paragraphs are practically unreadable. I would recommend a professional proof editing from English native speakers. As an example:
* abstract: “Pressure contours are not presented as obvious anisotropic characteristic while they are presented as isotropic characteristic under blow-off impulse effect. It indicates characteristic of composite material is presented as anisotropic in low pressure while it is presented as isotropic in high pressure.”
* line 54-55: " under the action of lightning strike and abundant achievements have been achieved."
* line 87: "most importantly"
* line 333-341: "What’s more, pressure around blow-off impulse area presents isotropic but not anisotropic characteristic, which agrees well the characteristic that composite materials present anisotropic in low pressure while isotropic in high pressure. Figure 16 presents the contours of Mises stress and pressure in ribs and strippers, which can be seen that Mises stress and pressure in ribs and strippers are very small and no elements are deleted in surface of ribs and strippers, but there are elements deleting in internal of ribs and strippers, as shown in Fig.12, indicating that blow-off impulse effect causes serious influence on the center areas in the top 6 layers of benchmark skin, but the influences on ribs, strippers and the rest areas are less serious relatively."
Author Response
Response to Reviewer 2 Comments
Open Review (x) I would not like to sign my review report
( ) I would like to sign my review report
English language and style (x) Extensive editing of English language and style required
( ) Moderate English changes required
( ) English language and style are fine/minor spell check required
( ) I don't feel qualified to judge about the English language and style
Yes | Can be improved | Must be improved | Not applicable | |
Does the introduction provide sufficient background and include all relevant references? | ( ) | (x) | ( ) | ( ) |
Is the research design appropriate? | ( ) | ( ) | (x) | ( ) |
Are the methods adequately described? | ( ) | ( ) | (x) | ( ) |
Are the results clearly presented? | ( ) | (x) | ( ) | ( ) |
Are the conclusions supported by the results? | ( ) | (x) | ( ) | ( ) |
Reviewer #2: Comments and Suggestions for AuthorsThis paper presents a numerical analysis on the effect of lightening strike to composite reinforced panel.
The main topic is interesting, but the paper need major improvements in order to reach a the scientific level of an international publication.
However, the remarks below are provided in order to improve the paper: (Both editorial and technical comments are given in the order they appear in the text.)
Point 1: -line 14-> Please change "Mises" into "von Mises"Response 1: Relative revision has been made in our manuscript.
Point 2: -line 119-> Please change "temperature-dependent" into "temperature- dependence".Response 2: Relative revision has been made in our manuscript.
Point 3: -line 121-> Please accurately define what is the considered composite material and report this definition also in the tables 1-3 captions.
Response 3: Relative revision has been made in our manuscript.Point 4: -line 127, Section 2.2-> Please define the adopted software (I imagine that it is Ansys) and the mesh characteristics. I mean, what is the time step? And how did the authors select it? How many elements for each layer? How many degree of freedom per element etc. In addition please give information about the computational cost of the model.Response 4: Relative revision has been made in our manuscript. The time step is selected according to our experience in previous works. Electric-thermal coupling module and blow-off impulse module are decoupled in this study. Lightning current is divided into 12 steps to load and sub-time step is equal to 10 in each load step. So, there are 120 steps in total and computation time is just 80μs in electric-thermal coupling module. Calculation results in this module can be completed within 3 hours. In blow-off impulse module, there are 22 output steps and solution time is 2μs, this module can be completed within 1 hour. So, computational cost of the model can be finished within 4 hours in total.
Point 5: -line 138, Figure 1-> Please introduce the geometrical dimensions also in this figure.Response 5: Relative revision has been made in our manuscript.
Point 6: -line 175-> What is the meaning of "JWL" acronym?Response 6: Relative revision has been made in our manuscript. "JWL" is the name of an equation of state in keyword user’s manual of ANSYS/LS-DYNA, which means "Jones-Wilkins-Lee" equation of state.
Point 7: -line 179-> What does 59# represent?Response 7: Relative revision has been made in our manuscript. 59# represents that material type of Mat_composite_failure_solid_model ranks No.59 in keyword user’s manual of ANSYS/LS-DYNA.
Point 8: -line 183-185-> What is the adopted reference system? Please clarify it with reference to the fiber orientation.Response 8: The reference system of this model is the global coordinate system in ANSYS software, fiber orientation is defined through establishing a local coordinate system in each layer. When yield function is used, stress components of each element should be transformed to the corresponding material principal axis in each layer. In this paper, X represents the fiber orientation, Y represents perpendicular to fiber orientation in-plane and Z represents perpendicular to fiber orientation out-plane. S is shear direction.
Point 9: -line 188, Figure 4-> What are the information exchanged between the two modules? Did the authors manually perform the exchange of information or is it automatic?Response 9: The information exchanged between two modules is about element type and material model. As it is described in our manuscript, element type is SOLID69 in electric-thermal coupling module. When electric-thermal coupling analysis is finished, blow-off impulse elements are selected and then SOLID69 is replaced by SOLID164 in blow-off impulse module for all the elements of composite reinforced panel. At the same time, high-explosive material model is defined in blow-off impulse area and Mat_composite_failure_ solid_model is defined in the areas except for blow-off impulse area. At this time, the exchange of information between the two modules is completed and all the information is manually performed.
Point 10: -line 191, Section 3-> Without a thorough model validation using experimental results (or other numerical models available in literature) it is difficult to assess the quality of the presented numerical results. This is one of the main weak point of the paper. I consider this point of paramount relevance for my judgement on the paper.Response 10: Blow-off impulse effect is an important dynamical damage response of composite materials according to lightning strike experiment. The previous works mainly focus on the lightning ablation damage of composite materials. The blow-off impulse effect is rarely studied, the relative reports hasn’t been seen. Obvious fiber fracture, dissipation and cocking phenomenon can be observed in lightning strike experiment. These damage modes can also be attributed to thermal explosion effect within materials. So, lightning strike damage cannot be analysed by ablation damage only. The simulation method proposed in our manuscript can well consider thermal explosion effect within materials. Simulation results can well reflect the bulge phenomenon around lightning attachment area. So, our numerical model is valuable although there are no experimental results supported at present.
Point 11: -line 201->Please report the temperature unit of measure in the legend or figure captions. The same point is valid for Figure 6 and 8.Response 11: Relative revision has been made in our manuscript.
Point 12: -line 203-> Did the authors check the quality of this result (max temp= 83937.3℃) comparing it with known result published in literature? Are the authors sure that this result is not biased by a poor mesh quality?Response 12: As failure for elements exceeding 3316℃ is not defined, elements deletion is not considered in electric-thermal coupling module. Energy disposition will continue to increase with the time increasing subject to lightning strike. Then it causes a sharply rise of temperature around attachment area. So, the highest temperature may reach 83937.3℃. The model in our manuscript is divided by hexahedral elements. At the same time, element dimension and mesh density are appropriate for this model, which can guarantee the calculation precision. The calculation time will increase dramatically if mesh density is larger.Point 13: -line 208-> Please be consistent with the notation, please change "Fig.6 and Fig.7" into "Figure 6 and Figure 7".Response 13: Relative revision has been made in our manuscript.
Point 14: -line 215-> I would like to know if the solid69 element is capable of accounting different fiber orientation for different layer? Please clarify how is built the model, there is one layer of element for each layer of fibers? Or there is another strategy? I imagine that the solid model can homogenize the behavior of multiple layers but how is possible that an homogenized model have different layer of stress or thermo-mechanical properties? Please clarify.Response 14: According to keyword user’s manual of ANSYS/LS-DYNA and other published literatures, solid69 element is capable of accounting different fiber orientation for different layers. The modelling methods for composite materials exist in ANSYS software. When composite materials model is established, each layer can be built through a solid and is defined as a part through APDL language. Size of the solid in each layer is equal to the geometrical dimension of each layer. Then, the stacking sequence in each layer can be defined through establishing a local coordinate system. When the model is meshed, there is one layer of elements for each layer of fibers, respectively. It is that the number of element division is equal to one in thickness direction of each layer. As the stacking sequence of each layer is different, fiber orientation of each layer is set and then material properties of composite materials are defined. When calculation is done, calculation results of each layer can be extracted through APDL language. As the stacking sequence in each layer is different, calculation results of each layer will be different too. Thus, the results can present the stress and thermo-mechanical properties of different layers.
Point 15: -line 257, Section 3.2-> Please give all the details of the numerical analysis: time step, element dimension, non linear solver etc. Then, is there any other load in addition to the blow-off? I mean, gravitational load.. etc.Response 15: Relative revision has been made in our manuscript. Element dimension and meshing method have described in Section 2.2. In our manuscript, we mainly study the blow-off impulse effect of composite reinforced panel induced by lightning strike. Other loads have little influence on calculation results. So, other loads are neglected.
Point 16: -line 267-> Please change "Mises" into "von Mises"Response 16: Relative revision has been made in our manuscript.
Point 17: -line 269-> Please clarify what is the collapse criterion. How are deleted the elements? Is the mesh modified at each time step?Response 17: As it is expressed in Eq.(3), Mat_composite_failure_solid_model can be used to build the yield function through strength parameters and stress tensor of composite materials. The elements will enter plastic phase when f is greater than zero. Then the elements will deform continuously subject to external load and the stiffness will be reduced too. The maximum failure strain is defined in keyword file of ANSYS/LS-DYNA. If the equivalent strains of the elements are greater than the maximum failure strain, then the elements will be deleted. Since there are no non-convergence and negative volume phenomena at each time step during numerical calculation, the meshes will not be modified at each time step.
Point 18: -line 271-> Please change "Mises" into "von Mises"Response 18: Relative revision has been made in our manuscript.
Point 19: -line 312-> Please use the same legend scale for each sub-figure in order to easily compare the results.Response 19: Relative revision has been made in our manuscript.
Point 20: -line 336-> Please change "Mises" into "von Mises"Response 20: Relative revision has been made in our manuscript.
Point 21: -What are the main advances in science produced by this paper? What are the novelty presented to the scientific community? I can see the use of a commercial software on a known problem, what is the original part?Response 21: Our paper can reveal dynamical damage mechanism of composite materials induced by lightning strike from the perspective of thermal explosion. The novelty of our manuscript is to propose a new method integrating electric-thermal coupling with explicit dynamic to study blow-off impulse effect of composite materials. The original part in our paper is to develop and realize a calculation process for blow-off impulse effect. The calculation process is divided into electric-thermal coupling module and blow-off impulse module, in which each module has its own analysis process and subroutines. Blow-off impulse effect of composite materials induced by lightning strike can be studied through combining with the analysis process and these subroutines.
Point 22: -The overall grammar and sentence construction is very poor. Some paragraphs are practically unreadable. I would recommend a professional proof editing from English native speakers. As an example:
* abstract: “Pressure contours are not presented as obvious anisotropic characteristic while they are presented as isotropic characteristic under blow-off impulse effect. It indicates characteristic of composite material is presented as anisotropic in low pressure while it is presented as isotropic in high pressure.”
* line 54-55: " under the action of lightning strike and abundant achievements have been achieved."
* line 87: "most importantly"
* line 333-341: "What’s more, pressure around blow-off impulse area presents isotropic but not anisotropic characteristic, which agrees well the characteristic that composite materials present anisotropic in low pressure while isotropic in high pressure. Figure 16 presents the contours of Mises stress and pressure in ribs and strippers, which can be seen that Mises stress and pressure in ribs and strippers are very small and no elements are deleted in surface of ribs and strippers, but there are elements deleting in internal of ribs and strippers, as shown in Fig.12, indicating that blow-off impulse effect causes serious influence on the center areas in the top 6 layers of benchmark skin, but the influences on ribs, strippers and the rest areas are less serious relatively."Response 22: Relative revision has been made in our manuscript. Additionally, we also invite a professor with good English writing to help us to modify the whole paper.
Author Response File: Author Response.doc
Reviewer 3 Report
This paper presents results on numerical analysis that was conducted to evaluate response of composite panels under effects of lightening strikes. The authors are encouraged to revised their works according to the following items/questions.
Major Questions, Comments and Concerns
1) How does the effects of thermal damage differ in the case of lightening strikes as compared to that from traditional thermal loading such as fire? Please add few lines on this aspect.
2) Tables 1 and 2 seem to be missing data on thickness.
3) The applied temperature from lightening strikes (of about 80,000°C) seems to be higher than average lightening temperature of about 50,000°C. Is there any justification for this?
4) What is the expected degradation in material properties of panels due to the rise in temperature/lightening? Please provide a list of thermal and mechanical properties if applicable.
5) Were the elements deleted manually? Or were they automatically deleted upon reaching a certain temperature? The discussion on this aspect can use some refinement and addition of clear discussion.
6) A question arises, what would be the effect of impulse (i.e. loss of elements) on mechanical properties/structural response of the panels? Will this significant affect the structural integrity?
Author Response
Comments and Suggestions for Authors
This paper presents results on numerical analysis that was conducted to evaluate response of composite panels under effects of lightening strikes. The authors are encouraged to revised their works according to the following items/questions.
Major Questions, Comments and Concerns
Point 1: How does the effects of thermal damage differ in the case of lightning strikes as compared to that from traditional thermal loading such as fire? Please add few lines on this aspect.
Response 1: Relative revision has been made in our manuscript. Thermal damage induced by lightning strike attributes to ablation, phase-transition, thermal shock and blow-off impulse effect, etc. While traditional thermal loading such as fire does not include dynamical effects of thermal shock and blow-off impulse, etc.
Point 2: Tables 1 and 2 seem to be missing data on thickness.
Response 2: Because carbon fiber/epoxy composite materials can be regarded as transverse isotropic ones, the values of the thickness column are the same as those of transverse column. Therefore, we combine them into one column.
Point 3: The applied temperature from lightning strikes (of about 80,000°C) seems to be higher than average lightening temperature of about 50,000°C. Is there any justification for this?
Response 3: Because the failure for elements exceeding 3316℃ is not defined in electric-thermal coupling module, elements deletion is not considered. Therefore, energy disposition will continue to increase with the time increasing subject to lightning strike. Then it causes a sharp rise in temperature of each element around attachment area. So, the highest temperature may reach 83937.3℃ and higher than average lightening temperature such as 50,000°C.
Point 4: What is the expected degradation in material properties of panels due to the rise in temperature/lightning? Please provide a list of thermal and mechanical properties if applicable.
Response 4: Relative revision has been made in our manuscript.
Point 5: Were the elements deleted manually? Or were they automatically deleted upon reaching a certain temperature? The discussion on this aspect can use some refinement and addition of clear discussion.
Response 5: Relative revision has been made in our manuscript. Failure elements are deleted automatically. Failure elements are not defined upon reaching a certain temperature while they are defined upon the maximum failure strain. As it is expressed in Eq.(3), Mat_composite_failure_solid_model can be used to build the yield function through strength parameters and stress tensor of composite materials. The elements will enter plastic phase when f is greater than zero. Then the elements will deform continuously subject to external load and the stiffness will be reduced too. The maximum failure strain is defined in keyword file of ANSYS/LS-DYNA. If equivalent strains of the elements are greater than the maximum failure strain, the elements will be deleted.
Point 6: A question arises, what would be the effect of impulse (i.e. loss of elements) on mechanical properties/structural response of the panels? Will this significant affect the structural integrity?
Response 6: Blow-off impulse induced by lightning strike will cause delamination, bulking damage and internal implosion within composite materials, which will aggravate damage degree and reduce mechanical properties or structural response of composite panels. So, it will affect the structural integrity greatly.
Author Response File: Author Response.doc
Round 2
Reviewer 2 Report
This paper presents a numerical analysis on the effect of lightening strike to composite reinforced panel.
I appreciate the work done by the authors to improve the paper, but the main weak points are still present.
Point 10: -line 191, Section 3-> Without a thorough model validation using experimental results (or other numerical models available in literature) it is difficult to assess the quality of the presented numerical results. This is one of the main weak point of the paper. I consider this point of paramount relevance for my judgement on the paper.
Response 10: Blow-off impulse effect is an important dynamical damage response of composite materials according to lightning strike experiment. The previous works mainly focus on the lightning ablation damage of composite materials. The blow-off impulse effect is rarely studied, the relative reports hasn't been seen. Obvious fiber fracture, dissipation and cocking phenomenon can be observed in lightning strike experiment. These damage modes can also be attributed to thermal explosion effect within materials. So, lightning strike damage cannot be analysed by ablation damage only. The simulation method proposed in our manuscript can well consider thermal explosion effect within materials. Simulation results can well reflect the bulge phenomenon around lightning attachment area. So, our numerical model is valuable although there are no experimental results supported at present.
**** The model is not reliable in my opinion without accurate validation.
----------------
Point 12: -line 203-> Did the authors check the quality of this result (max temp= 83937.3℃) comparing it with known result published in literature? Are the authors sure that this result is not biased by a poor mesh quality?
Response 12: As failure for elements exceeding 3316℃ is not defined, elements deletion is not considered in electric-thermal coupling module. Energy disposition will continue to increase with the time increasing subject to lightning strike. Then it causes a sharply rise of temperature around attachment area. So, the highest temperature may reach 83937.3℃. The model in our manuscript is divided by hexahedral elements. At the same time, element dimension and mesh density are appropriate for this model, which can guarantee the calculation precision. The calculation time will increase dramatically if mesh density is larger.
**** This result seems not reliable. Probably a sensitivity analysis on the mesh is required.
------------------------
Point 21: -What are the main advances in science produced by this paper? What are the novelty presented to the scientific community? I can see the use of a commercial software on a known problem, what is the original part?
Response 21: Our paper can reveal dynamical damage mechanism of composite materials induced by lightning strike from the perspective of thermal explosion. The novelty of our manuscript is to propose a new method integrating electric-thermal coupling with explicit dynamic to study blow-off impulse effect of composite materials. The original part in our paper is to develop and realize a calculation process for blow-off impulse effect. The calculation process is divided into electric-thermal coupling module and blow-off impulse module, in which each module has its own analysis process and subroutines. Blow-off impulse effect of composite materials induced by lightning strike can be studied through combining with the analysis process and these subroutines.
*** Main advances are still poor from my point of view. The model requires accurate validation and the innovative parts are not sufficient for an international publication.
Author Response
Comments and Suggestions for Authors
This paper presents a numerical analysis on the effect of lightening strike to composite reinforced panel.
I appreciate the work done by the authors to improve the paper, but the main weak points are still present.
Point 10: -line 191, Section 3-> Without a thorough model validation using experimental results (or other numerical models available in literature) it is difficult to assess the quality of the presented numerical results. This is one of the main weak point of the paper. I consider this point of paramount relevance for my judgement on the paper.
Response 10: Blow-off impulse effect is an important dynamical damage response of composite materials according to lightning strike experiment. The previous works mainly focus on the lightning ablation damage of composite materials. The blow-off impulse effect is rarely studied, the relative reports hasn't been seen. Obvious fiber fracture, dissipation and cocking phenomenon can be observed in lightning strike experiment. These damage modes can also be attributed to thermal explosion effect within materials. So, lightning strike damage cannot be analysed by ablation damage only. The simulation method proposed in our manuscript can well consider thermal explosion effect within materials. Simulation results can well reflect the bulge phenomenon around lightning attachment area. So, our numerical model is valuable although there are no experimental results supported at present.
The model is not reliable in my opinion without accurate validation.
Response 10: At present, there are actually no experimental results on the study of blow-off impulse effect of composite materials induced by lightning strike. Lightning strike damage is a comprehensive result which includes ablation damage, phase-transition, thermal shock wave and blow-off impulse effect etc. Blow-off impulse effect is a key issue in lightning strike damage and is very difficult to measure by experimental method. In our manuscript, we propose a numerical method to predict the blow-off impulse effect of composite materials induced by lightning strike, which are seldom reported available in literatures.
Point 12: -line 203-> Did the authors check the quality of this result (max temp= 83937.3℃) comparing it with known result published in literature? Are the authors sure that this result is not biased by a poor mesh quality?
Response 12: As failure for elements exceeding 3316℃ is not defined, elements deletion is not considered in electric-thermal coupling module. Energy disposition will continue to increase with the time increasing subject to lightning strike. Then it causes a sharply rise of temperature around attachment area. So, the highest temperature may reach 83937.3℃. The model in our manuscript is divided by hexahedral elements. At the same time, element dimension and mesh density are appropriate for this model, which can guarantee the calculation precision. The calculation time will increase dramatically if mesh density is larger.
This result seems not reliable. Probably a sensitivity analysis on the mesh is required.
Response 12: Relative revision has been made in our manuscript. The sensitivity analysis on the mesh has been added in our manuscript. Finite element model of composite reinforced panel is divided by hexahedral elements and we try to make mesh density meet the requirement of numerical precision. Calculation errors will be larger indeed when element dimension changes. However, we find that numerical simulation will not be performed and calculation results cannot be obtained in our workstation if element dimension is smaller than that in our paper. So, we select the smallest element dimension within the range that our workstation can bear.
Point 21: -What are the main advances in science produced by this paper? What are the novelty presented to the scientific community? I can see the use of a commercial software on a known problem, what is the original part?
Response 21: Our paper can reveal dynamical damage mechanism of composite materials induced by lightning strike from the perspective of thermal explosion. The novelty of our manuscript is to propose a new method integrating electric-thermal coupling with explicit dynamic to study blow-off impulse effect of composite materials. The original part in our paper is to develop and realize a calculation process for blow-off impulse effect. The calculation process is divided into electric-thermal coupling module and blow-off impulse module, in which each module has its own analysis process and subroutines. Blow-off impulse effect of composite materials induced by lightning strike can be studied through combining with the analysis process and these subroutines.
Main advances are still poor from my point of view. The model requires accurate validation and the innovative parts are not sufficient for an international publication.
Response 12: Although there is no experimental validation in our study, numerical method proposed by us can provide a reference to research dynamical damage of composite materials induced by lightning strike. We thank the reviewer’s advice to revise our paper and hope to find a validation method in the future.
Author Response File: Author Response.doc
Reviewer 3 Report
Thank you for your efforts.
