Experimental Characterization of Screw-Extruded Carbon Fibre-Reinforced Polyamide: Design for Aeronautical Mould Preforms with Multiphysics Computational Guidance

Round 1

Reviewer 1 Report

1. The phrase of “Error! Reference source not found.”appeared many times in the manuscript, they should be corrected.

2. All the titles of the standards referred in Table 1 should be listed in the “References”.

3. When comparing the tensile properties, it was found that, at 180℃, the tensile strengths in the printing bead direction and the stack direction reduced to almost the same extent, however, at 80℃, the reduction differs greatly, in this situation, the reduction in the two directions is by 37% and 10%, respectively. How to explain? Additionally, both the tensile modulli at 80℃ and 180℃ in the stack direction are reduced more greatly that those in the printing bead direction, this phenomena should also be explained reasonably. Moreover, the significant decrease in both the tensile strength and tensile modulus with temperature should be explained.

4. Generally, at least five pieces of samples should be used for the mechanical properties test, error bar should be given when illustrating the test results of each kind of mechanical properties in figures.

5. Line 515, what is the basis for determining the minimum FoS as 2.8? How to get the FoS in this study?

6. The layout of lines 521and 522 should be reset.

7. In figure 8, it seemed that, the values of the modulli shown in the figure are not equal to those listed in the table at bottom. For example, the tensile modulus for the sample in the bead direction at RT shown in the figure is obviously smaller than 12GPa, while it is written as 12.10GPa in the bottom table. 

8. Figure 8 is drawn with a full border, while figure 9 without border, they should be shown in the same manner.

9. The contents in Table 6 should be rearranged.

10. The left picture in Figure 13 is almost the same with that shown in Figure 1. Please confirm its necessity. 

Author Response

Dear reviewer,

The authors appreciate very much your contributions and suggestions because they help to improve this paper. Also, an English native reviewer has checked the article improving its composition.

Please find in the attached file the details of how each point has been fully addressed.

Thank you very much in advance for your review.

Regards

Juan Carlos Antolin-Urbaneja

TECNALIA

Author Response File: Author Response.pdf

Reviewer 2 Report

1. The information of raw materials (PA6+CF) is needed.

2.  Line 272 “Additionally, tensile properties at room temperature (RT) are compared with that 272 published in the Technical Data Sheet of injected BergamidTM B70 KF20 Black by Avient.” Does the “injected” mean inject molding? Please include the data in main paper or support information. Why not prepare the molded samples (injection or compression molding) yourself to compare with the 3D printed samples?

3.  Figure 6, Table 1 introduce various characterization methods (flexural, shear, etc), The claim in Line 339 “The rest of properties generated during the current research are available on request.” is quite confusing. Please include all results in main paper or support information.

4.   What is the motivation to include the computer modeling in this paper? What is the relation between 3D printing and the computer modeling?

5. the introduction and conclusion need to be more concise.

Author Response

Dear reviewer,

The authors appreciate very much your contributions and suggestions because they help to improve this paper. Also, an English native reviewer has checked the article improving its composition.

Please find in the attached file the details of how each point has been fully addressed.

Thank you very much in advance for your review.

Regards

Juan Carlos Antolin-Urbaneja

TECNALIA

Author Response File: Author Response.pdf

Reviewer 3 Report

In this manuscript, Polyamide 6 reinforced with carbon fibre is applied as material for aeronautical purposes. The application of 3D printing techniques allows the production of tailor-made devices that are extensively analysed to evaluate the mechanical, density and porosity properties, with a final evaluation of possible problems and the relative solution to overcome them. In general, the manuscript is well-written and is worth being published.

There are some issues that should be addressed before publication:

1.       The introduction is too long, and the data reported for comparison should be included in a Table to allow a better understanding of the context of this work.

2.       Why room temperature, 80°C and 180°C were chosen as relevant temperatures?

3.       There are no indications about how they prepared the polyamide 6 reinforced with carbon fibre or if they bought it from a supplier (in case, please indicate the specific properties of the product).

4.       They classified the product as semi crystalline. Was Differential Scanning Calorimetry (DSC) carried out to evaluate the properties of the 3D printed polymer?

5.       “Material Characterization” should be Section 3.1 and not 2.1.

6.       In Figure 5 the ruler is not clear, please can you insert a scale? Same considerations also for Figure 5c (the right one) that show no scale bar.

7.       In Section 4.1, lines 333-334 the authors referred to other possible data available on request. If there are some relevant data about material characterizations, they can be included in a Supporting Information

8.       The final properties required from end users, for the eventual real application of polyamide 6 with carbon fibre, are not clearly reported and the comparison among the obtained and expected features cannot be easily made.

9.       Please, check reference 8 (the last access is Aug 4 2003).

In general, thanks to the huge and in-depth characterizations carried out by the authors, the article resulted in many sections in which all data are examined in detail, demonstrating the applicability of Polyamide 6 with carbon fibre as reinforcing agent in 3D printing. Advantages respect to the materials usually used for these applications should better pointed out to clarify the applicability of this polymer in aeronautical applications.

Author Response

Dear reviewer,

The authors appreciate very much your contributions and suggestions because they help to improve this paper. Also, an English native reviewer has checked the article improving its composition.

Please find in the attached file the details of how each point has been fully addressed.

Thank you very much in advance for your review.

Regards

Juan Carlos Antolin-Urbaneja

TECNALIA

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The previous questions and concerns have been addressed. However, please include the Q3 answer in the main paper.

Author Response

Dear reviewer,

The authors appreciate very much your suggestion. The given explanation in previous review has been included in the main paper. Therefore, in Line 349, we have added the following sentence (highlighted in green): “They are included in a registered software as part of TECNALIA´s intellectual property.”

The authors hope that questions and concerns have been addressed.

Thank you very much in advance.

Regards

Juan Carlos Antolin-Urbaneja

TECNALIA