Buckling Test of Composite Cylindrical Shells with Large Radius Thickness Ratio
Round 1
Reviewer 1 Report
The authors analyze the influence of the ratio between radius and thickness on the evaluation of the knockdown factor (i.e. the ratio of the experimental buckling load and theoretical buckling load) of cylindrical CFRP shells under axial compression. In particular, the effect of different positions of the point of application of the load, and the effect of the shape imperfections are taken into account. The following minor revisions are suggested:
- The introduction of this manuscript can be improved by considering additional studies available in the literature
- some sentences are not clear, such as “Buckling of composite cylindrical shells under axial compression with r/t = 893 was investigated to investigate the radius-thickness ratio (r/t)”.
- Please explain how the theoretical buckling load was evaluated, and how the effect of shape imperfections was considered, both from a theoretical and experimental point of view. These aspects are not clear.
- explain better the meaning of the offset degree of the load center.
- Figures 19-26 should be improved by adding the axis titles and the unit of measure and making clear the meaning of the numbers in legend.
Author Response
Please see the attachment.
Author Response File: 
Author Response.docx
Reviewer 2 Report
The manuscript is dedicated to the experimental study of the performance of the thin-walled cylinders made of CFRP with radius-thickness ratio more than 850 under the buckling load tests and focused on obtaining dependence between Knockdown Factor (KDF) and radius-thickness ratio. As studied material appears to have significant application in most field of the industry this study appears to be important and actual.
Revealed decreasing of the KDF with the growing of radius-thickness ratio appears to be a new result provided in the manuscript.
A comprehensive description of all aspects of performed tests including detailed preprocessing of such delicate samples, control of specimen shape, test setup and test procedure itself appears to be the strongest part of the manuscript.
Some significant weaknesses and issues of the manuscript should be also underlined.
1. The manuscript provides no theoretical basis except exact value referenced to previous studies for calculation of theoretical bucking loading used to calculate KDF. I suggest providing at least a brief overview of the theory and steps to obtain used value. Nature of this value is also mandatory for placing obtained data on figure 27 into comparison with data from independent sources.
2. Figure 27 appears to be a revision of figure 2 updated with new data collected in the manuscript and in previous studies of its authors. Figure 2 was also obviously prepared to plot NASA SP-8007 curve from figure 1 on it, but this curve is absent which makes figure 2 to look odd. This two fact and poor quality of figure 2 make the need for the presence of this figure in the manuscript debatable. I suggest the authors of the manuscript consider the need for the presence of this figure.
3. Manuscript provides no information about measurement errors meet during the tests. So it makes it difficult for example to determinate segregation of the load values on figures 15-18.
4. As a big body of data on shape imperfections was collected during the test some quantitative metrics on it should be taken into consideration during data analysis.
5. Figures 20, 23 and 24 provide imperfection profiles which look the same. If there is the same profile on these three figures they should be merged into the single one providing information on tests of the first sample. The same procedure should be considered for figures 22, 25 and 26.
6. Figures 15-26 require a more detailed explanation of their contents in the captions.
7. I also noticed some inconsistencies in the text of manuscript which actually may be typos but may significantly skew the text. Here two of them looking most noticeable. Line 52 of the manuscript references the origin of figure 2 as [7] but the caption of this figure on line 54 provides a reference to the source [6]. Figures 25 and 26 have the same caption (see lines 194 and 195). These two examples demonstrate the necessity of additional proofreading of the manuscript.
A low number of tested samples may be considered as an inextinguishable disadvantage of the study provided in the manuscript but it provides proof-of-concept results and may still be published after elimination of noticed issues and providing the strong theoretical base in it.
Author Response
Please see the attachment.
Author Response File: Author Response.docx
Round 2
Reviewer 2 Report
Authors did improve the quality of the manuscript significantly. And I think it now may be accepted for publication.
