Surface Pretreatment and Fabrication Technology of Braided Carbon Fiber Rope Aluminum Matrix Composite

Round 1

Reviewer 1 Report

The submitteed manuscript deals with the surface treatment copper coating by electroless plating and incorporation into MMC of braided carbon fibers.

The concept as such is interesting. Carbon fibers are first de-sized than treated by diffent chemical methods to enhance surface activity and subsequently copper-coated by electroless plating to enhance bonding to the aluminium matrix and suppress formation of Al4C3 at the carbon aluminium interface, which inevitably happens in uncoated state. 

The main focus and the majority of experiments and results are presented for the surface treatment processes. This part of the paper is OK.

The final manufacturing of the MMC is poorly described, only the general idea is presented. In so far the results in Fig.11 are difficult to evaluate and reproduce. Moreover it is just one test that was performed, effects such as mis-alignment or positioning problems in the mold might be much more significant than the difference between the different materials, so this experiment has the character of a preliminary test, its results should not be overstressed.

Some general remarks:

the English does need improvment, it is understandable what the authors want to express but is is by far not sufficient.

Some results are given with five digit accuracy (e.g. page 13 line 339), this makes no sense and by far exceeds the measurement accuracy, three digits are enough in case of a single experiment with not statistical coverage 2 digits are enough.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

This manuscript presents the results of experimental studies on braided carbon fiber-reinforced Al composites. The surface of carbon fibers are modified with copper to improve the interaction with the metal matrix. Various experiments are carried out to control and characterize the fiber coating of fiber. The results of tensile test on composite specimens is also presented. However, the manuscript requires major revisions before being considered for publication in Metals.

- In manufacturing of composites, entrapment of voids within fibers (intratow voids) is always a major issue. In this work, void formation is not controlled and it is not clear what the effect of braiding is (compared to simple tows) in void formation and the quality of resulting composites.

- Composite samples are produced by placing one bundle or rope of fibers in the center of a mold, resulting in very low fiber volume fractions. Why did not the authors consider higher volume fractions of fibers? It is hard to make any conclusions about composites if the reinforcement is localized and non-uniform, especially considering that there is no information about void content and distribution.

- How many samples were tested for mechanical testing? The fabrication and testing procedure should be explained in more details. Again, by just looking at stress-strain curve for one specimen, no scientific conclusions can be made.

- Why adding fibers (bundle or braided) results in improved strength but not modulus? The rule of mixer is more valid for modulus than strength but no effect is seen here for modulus!

- In the last paragraph of page 7, authors mention that the coating thickness should be 0.5 to 1 micron. How did they choose this number? If there any scientific evidence for this claim?

- The structure of coating in fig. 2 is non-uniform but more ordered in fig. 3. Is the difference due to different levels of pH in surface modification? If so, it is suggested that the analyses be done on similar specimens.

- To show the effectiveness of surface coating and fiber pattern, more control experiments are required in mechanical tests: Coated and uncoated braided fibers, coated and uncoated fiber bundle (tows). It is hard to make any conclusions without enough control specimens. Also, it is not clear if the fiber bundle used in the tensile test was coated or uncoated.  

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors have made many changes which helped improve the manuscript.

One issue is still insufficient and should be improved. In the first review I mentioned that the authors should not give measured values four of even more significant digits which exaggerates accuracy.

Some values were corrected, at the same time it seems the meaning of my comment was not fully understood.

Authors should always consider the limits of the individual measurements and the standard deviations between groups of experiments.Values and accuracy must be in the same order of magnitude.

So if you can measure with an accuracy of 5 % and the standard deviation is 5 % you cannot give numbers in an accuracy exceeding 1%.

Examples from the text:

line 169: ...thickness ranges from 614.44-797.62 nm...

If you have a good SEM you may be able to measure +/- 10 nm so the maximum accuracy is 610-800 nm (two significant digits)

line 345-347: strength is 69 MPa (corrected from the original OK) ... 30.55 % higher than...

If you give the strength in two digits give the increment rounded to two significant digits => 31 %

Authors are requested to go through their manuscript again and check all numbers for plausibility of the accuracies given.

 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Authors have addressed the comments in the revised manuscript.

Author Response

Thank you for the comments concerning our manuscript. Those comments are all valuable and helpful for improving our paper.

Thank you again for your valuable comments.