Cumulative Shear Damage Mechanism to Short Fiber Type C/SiC

Round 1

Reviewer 1 Report

This study “Cumulative Shear Damage Mechanism to Short Fiber type C/SiC” focuses on the cumulative shear damage behavior and mechanisms of short fiber type C/SiC by conducting loading–unloading tests and by measuring the stress–strain relations. Here are my comments and questions:

1. authors should describe the novelty of the work and the difference between this work with other similar research. There are several works published with this subject. The abstract must be rewritten.

2.The authors should review the other new investigation on their study way in the introduction part and finally note the novelty of the manuscript. The introduction part needs to develop.

3- Provide characterization tests for the materials used.

4. - The language used in the manuscript can be more specific to the scope and aim of the study.
5. In test methods, authors should introduce all of the instruments and devise used in this research. Also, the manuscript needs to figure of the materials used with scale.
6. The result of “Comparison of peak strain and permanent strain” is superficial. The authors should try to provide more explanations.
7. - page 9, the authors said:” After fracture, cracks propagated perpendicularly to the tensile direction from the notch. Comparing the crack locations found before and after fracture, some of them correspond well, which also suggests that fracturing was caused by linkage of propagating cracks”, how can authors prove this?
8. The conclusion section is very general. Must be rewritten and revised.
9. The authors should indicate experimental errors throughout the paper.

Author Response

1. Authors should describe the novelty of the work and the difference between this work with other similar research. There are several works published with this subject. The abstract must be rewritten.
2. The authors should review the other new investigation on their study way in the introduction part and finally note the novelty of the manuscript. The introduction part needs to develop.
3. The language used in the manuscript can be more specific to the scope and aim of the study.
4. The conclusion section is very general. Must be rewritten and revised.

(l. 8-18, 35-77, 415-428) We deeply regret less impressive abstract, conclusion and ambiguous introduction of the previous version of the paper. The revised paper tried to emphasis on the importance and novelty of current study in that this study can predict shear stress-strain relation of randomly oriented short fiber reinforced ceramic matrix composite from measured damage characteristics, which is profitable for nondestructive health monitoring technique().

 

3 Provide characterization tests for the materials used.

5. In test methods, authors should introduce all of the instruments and devise used in this research. Also, the manuscript needs to figure of the materials used with scale.

(l. 80-98, 102, 129-131, 145-150) We added material, shear loading test configuration and image analysis information into the section of “Materials and Methods” . Besides, we put scale in to Figure 11.

 

6. The result of “Comparison of peak strain and permanent strain” is superficial. The authors should try to provide more explanations.

(l. 200-206) We added explanations, comparing these behaviors to those reported in the previous works.

 

7. page 9, the authors said:” After fracture, cracks propagated perpendicularly to the tensile direction from the notch. Comparing the crack locations found before and after fracture, some of them correspond well, which also suggests that fracturing was caused by linkage of propagating cracks”, how can authors prove this?

(l. 227-228) We agree the jump of logic of this sentence. We put complemental sentence that based on the crack propagation behavior in micro scale.

 

9. The authors should indicate experimental errors throughout the paper

Basically, we tried to put error bars in all the data to tell the truth as it is. However, we are afraid that regarding Figure 13 and 14 only one sample was obtained at some close stress levels to the overall fracture. Some data have no error bar because other samplesfractured earlier.

Author Response File: Author Response.docx

Reviewer 2 Report

Title: Cumulative Shear Damage Mechanism to Short Fiber type C/SiC

Authors: Yuta Tobata, Shinsuke Takeuchi, Ken Goto

Manuscript number: jcs-1292899

General comments:

The authors studied apparent and unloaded modulus of C/SiC short fiber experimentally. The manuscript is well written. The authors explained the test details clearly. I don’t have any major comments but with a few minor suggestions before accepting the manuscript for publication.

Specific comments:

• Line 36, can you please briefly explain what is “apparent modulus”? also, line 38, “unload modulus”?
• Line 39, in addition to “Observation of crack propagation processes suggests that this reason 39 is the lack of fiber fracture and crack propagation between transverse fibers.”, what about matrix crack?
• Why to italicize lines 83-84?
• Could you please comment the role of using progressive damage analysis to explain the nonlinear relation of stress-strain presented in Figures 3, 4 and 6?

 

 

 

 

Author Response

Line 36, can you please briefly explain what “apparent modulus” is? 　also, line 38, “unload modulus”?

(l. 37-40) The “apparent modulus” was calculated from the slope between the points of peak stress and the end of unloading of each cycle. The “unloading” modulus was calculated from the tangent of stress-strain curve in unloading. In the static condition, unloading modulus is true. However, during the dynamic deformation process of unloading, nonlinear stress-strain behavior starts because of crack closing, which causes the difference from the true modulus. Therefore, we call the modulus, “Apparent”.

Considering this comment, we put information on the definition of “unloading modulus” and “Apparent modulus”.

 

Line 39, in addition to “Observation of crack propagation processes suggests that this reason 39 is the lack of fiber fracture and crack propagation between transverse fibers.”, what about matrix crack?

(l. 40-42) We are sorry for the lack of information. The crack actually propagated in the matrix phase but also fiber-matrix interface. It was difficult to distinguish the propagation area precisely during observation. Therefore, we explained the crack as “crack propagation between transverse fibers”.

 

Why to italicize

(l.98-99) We deeply apologize the mistake. We have changed the font style.

 

lines 83-84? Could you please comment the role of using progressive damage analysis to explain the nonlinear relation of stress-strain presented in Figures 3, 4 and 6

We believe that this proposed damage mechanics model is profitable for the nondestructive health monitoring for verifying the threshold of the failure risk. To assess the risk, we think it is a reasonable to predict these stress-strain relations of 1 cycle loading-unloading and its variation affected by the increase of the peak stress for the first step. Once we obtained prediction model of 1 cycle, it is expected that the model is applicable to prediction of life span under fatigue test.

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

The comments of my first report have been addressed by the authors.

Reviewer 2 Report

Thanks the authors for taking care of my comments and questions. I am glad to accept this revised manuscript.