Development of Fiber-Reinforced Polymer Composites for Additive Manufacturing and Multi-Material Structures in Sustainable Applications

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Comments to authors:

I believe that some statistical analysis of results should be provided to evaluate the methods presented.

Does Figure 10 provides one of the three testing for each material, or is it averaged?

What is the statistical significance of the data reported in tables?

Error bars should be provided for figure 16.

 

 

Author Response

Please find the response to the reviewer's comments in the attached file.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The current title of the paper is too long. The title needs to be concise and should provide the overview of the work presented in the research paper.

Abstract includes too many abbreviations; it is difficult to understand the main findings of the study.

The full form of the abbreviations must be defined, when the abbreviation is first used in the text.

The ASTM and ISO tests have been incorrectly cited in the text, please stick to the Numbered reference style.

The stress-strain curves in the Figures 9,  10 and 11, should start from 0-0 origin. All curves need to be corrected.

Testing standards have not been mentioned in the reference list at the end of the paper.

 

 

Author Response

Please see the response to the reviewer's comments in the attached file.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

A major revision is required to improve the quality of the work. The revised manuscript may be examined for final recommendation.

Comments   

·       Avoid using acronyms/abbreviations in title

·       Minimize using acronyms/abbreviations in Abstract and define them upon first appearance.

·       Too many acronyms/abbreviations! Quite confusing! Try to minimize them. Also prepare a list for all necessary acronyms/abbreviations in the beginning of paper after Abstract.

·       An extensive improvement in English language is necessary. Try to increase the consistency and fluency of the sentences/text. Correct typo and grammar errors accordingly.

·       Introduction should be concise and exhaustive including all relevant studies up to date. Some main relevant literature should be reviewed in introduction.

·       Which gap does this study fill in the field? The novelty of the work should be clearly highlighted, emphasized and compared with literature.

·       Add more in detail information in experimental section for materials specification, methods, instruments, standard test methods, etc.

·       For recycled polymers, full information (molecular weight (MW, molecular weight distribution (MWD), melt flow index (MFI), rheological properties, FTIR, etc) should be added and compared with parent neat polymers.

·       Fiber-polymer interface interaction/binding play crucial role in composite performance and mechanical properties. Composite morphology of all samples should be characterized/addressed with FESEM and used for discussion on mechanical results and composite performance.

·       Reproducibility should be investigated. Number of measurements for each sample should be mentioned. Add standard deviations and error bars for all data and figures.

·       Discussion on the results must be critically improved. In current form, mostly the results are reported and no significant scientific discussion is made. Give frank reasons for the results and trend of data, try to justify the results scientifically and compare with literature.

·       The optimum processing parameters and processing condition for each sample should be given.

·       Cost analysis of the process should be done.

·       Conclusion should be strengthened and include all significant findings.

Comments on the Quality of English Language

·       An extensive improvement in English language is necessary. Try to increase the consistency and fluency of the sentences/text. Correct typo and grammar errors accordingly.

 

Author Response

Please see the response to the reviewer's comments in the attached file.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Manuscript ID: processes-3197489-peer-review-v1

Manuscript Title: Characterization and Development of Fiber-Reinforced Polymer Composites for FDM Processing and Functional Gradient Multi-Materials for Structural and Sustainable Applications

1.       In general, I recommend that the manuscript be more concise.

2.       It is better to rewrite the abstract. Do you mean percentage by weight or by volume? Is the type of fiber continuous or short? The first line of the abstract can be omitted. Does "rPLA" mean recycled PLA? It is better to express the tensile strength values ​​in terms of megapascals.

3.       The keywords "tensile filaments testing" and "3D-printed tensile and compressive testing" are unclear.

4.       The first paragraph in the introduction can be much more concise. It is not necessary to say many things. This is also true for the second paragraph.

5.       Table 1 can be integrated into the text.

6.       Parts of the description given about the "microscope" can be removed.

7.       Is the fiber used the same as the one used in reference 42? (Table 3)

8.       The selection of printing parameters in Table 5 requires discussion, reasoning, and reference.

9.       Figure 5 can be deleted.

10.   On what basis and reference have the Multi-Material Design samples been selected?

11.   It is better to present Figures 10 and 11 more professionally.

12.   Expressing Figure 16 A in terms of strain stress is better. It is necessary to add the error bar to Figures 16 b and c.

13.   In Figure 17, the failure areas are not clear.

 

14.   It is better to remove references before 2018 and replace them with new references.

Comments on the Quality of English Language

Check and correct grammatical errors throughout the manuscript.

Author Response

Please see the response to the reviewer's comments in the attached file.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

Before being considered for publication, the manuscript should be improved. Below are some observations that should be addressed, in my opinion.

·       The entire manuscript should be thoroughly reviewed to ensure that all acronyms are defined at their first appearance in the text and subsequently used consistently. For instance, FDM is defined multiple times, but then the full term is used again. The standard term MEX should replace FDM throughout the manuscript. Additionally, acronyms such as PCFPP are not explained and should be defined. A similar inconsistency is present with the term carbon fiber, which is referred to variably as CF, carbon, and carbon fiber. Consistent terminology should be used throughout. There is also inconsistency when referring to additive manufacturing and 3D printing. The standardized term AM should be used consistently throughout the manuscript, as 3DP is more colloquial. Please choose one term and use it consistently.

·       Tables 1 and 2 should be combined into a single table, as they present related information. Similarly, Figures 1 and 2 can be combined into one figure with appropriate annotations to streamline the presentation of data. In Figure 3, each image should be annotated properly, and the extruder, which is currently not visible, should be shown clearly—please replace the image accordingly.

·       The Introduction is rather long and contains repetitions and redundant text, such as in lines 53-57, where standards names are mentioned multiple times. These should be removed to improve clarity. Additionally, I could not identify any examples to justify the first statement in the abstract related to industrial and architectural contexts—this needs to be more specific (justify the title). For example, in line 66, the term "multiple approaches" is used without specifying which approaches are being referred to.

·       In the Materials and Methods section, there are many materials subjected to tests, some of which are purchased, while others are manufactured. Please add a schematic (roadmap) to clarify which materials are which—especially since CF-PLA, CF-PETG, and natural fibers were not actually produced. It is important to clarify which materials are used in multi-material designs and which in single-gradient designs, as it is currently difficult to follow the methodology.

·       Is there a reason why hemp was mixed with PLA and jute with PETG, and not vice versa? The filament compositions seem somewhat arbitrary, and the percentages of jute, CF, or hemp fibers are not justified. The diameter of the extruder nozzle should also be specified, especially since the diameters of the manufactured filaments are well below 1.75 mm—this requires an explanation.

·       The rationale for additionally reinforcing CF-PLA with more CF, as well as CF-PETG, should be clarified. In Tables 5 and 6, add parameters such as the number of perimeters and top/bottom layers, as well as the infill pattern in Table 5.

·       Were the produced filaments for the Bambu printer flexible enough to be placed on the spool and then used in the printing process? Please discuss any challenges encountered in this regard. In lines 256-262, it would be beneficial to present images from the slicer with the modality of designing the layers to supplement the information in Figure 6, as the differences are not quite visible. Assign a label or name to each sample to make it easier to understand which is which and to clearly indicate which combinations were covered. Use this sample notation consistently in Figure 6.

·       The discussion found in lines 295-317 should be moved to the Introduction and combined with lines 67-81, and make the text more concise and focused.

·       In Figure 8, the images should be taken from the front of the machine to better show the placement of the samples. It should also be clearly mentioned which sample is presented as an example.

·       Please clarify the difference between sections 2.5.2 and 2.5.3. Why are not just one section?

·       In the Results section, it is important to comment on the results shown in Figure 10 in comparison with the producer's data. Additionally, discussions of the results are mostly missing from this section—these should be added. Please explain whether the results are still reliable for the sample that failed outside the gauge zone, as seen in Figure 12.

·       Provide possible reasons for the observation in lines 412-413. For Figure 15, zoom in on the highlighted areas, as it is difficult to observe the details. Similarly, in Figure 17, the highlighted zones should be zoomed in for clarity.

·       Finally, explain the utility of the study. How can the results be practically used, especially considering that the re-manufactured filaments are custom in their composition and processing? The likelihood of actually using these non-commercial filaments is extremely low. Therefore, explain how the results can be more generally applicable, as they are currently too specific to provide significant scientific value. 

 

 F

Comments on the Quality of English Language

The sentences are too long. The text is redundant. More concision is required, especially in the Introduction section.

Author Response

Please see the response to the reviewer's comments in the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

Comments and Suggestions for Authors

Authors should note that just having limited time and lack of apparatus in your lab could not be right reason to let the work be incomplete. Authors may ask editor for more time and other colleagues in your country or other groups in abroad for assisting you with this analyses.

Authors should note that in the study of polymer blend/composite systems, both structure (MW, MWD, MFI, etc) and property (mechanical performance and physical characteristics) are indispensable and must be studied simultaneously. Otherwise the study would be incomplete and the trend of physical/mechanical data could not be precisely addressed and therefore work would lack scientific value.

One cannot exactly address the origin of mechanical results and trends of data unless you have precise/full information about the MW, MWD, MFI, rheological properties, etc (particularly for recycled polymers) and then make use them in discussion of mechanical data. It is not optional whether to include above mentioned data or as separate future study. Otherwise the study would be incomplete and lack significant scientific value (as current work is).

Therefore, it is strongly recommended to fully complete the pending tests in the comments and fully revise (major revision) your work accordingly. The revised work may be examined for final recommendation.

 

Comments   

·         It is well known that in recycling process, due to harsh thermal and mechanical actions, polymer undergoes degradation, chain scission, etc which result in significant changes in molecular weight, molecular weight distribution, rheological flow behavior, etc of recycled polymer. All these have significant impact on the performance/properties of final composite product. Therefore, MW, MWD, MFI, rheological properties (storage modulus, loss modulus, tan δ) data must be exhaustively investigated and added to this work and used in analysis and discussion on the mechanical performance of composite samples.

·         Optical microscopy is not suitable tool for interface binding/wettability of polymer blends/composites. Nothing is discernable/observable from optical microscopic images. Fiber-polymer interface interaction/binding play crucial role in composite performance and mechanical properties. Your discussion on mechanical data without these information is not logic nor scientific. In my view some discussions are not valid/correct in current form and must be well addressed of cited. It is strongly recommended composite morphology (FESEM) of all samples to be added to this work and used in analysis and discussion on the mechanical performance of composite samples.

·         Discussion on the results must be critically improved based on structure-property relationship of polymer composites and compared with literature.

·         The optimum processing parameters and processing condition for each sample should be given based on structural/morphological/rheological data.

·         Cost analysis of the process should be done.

·         Abstract and conclusion should be revised as per full revisions made.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

Manuscript title: Development of Fiber-Reinforced Polymer Composites for Additive Manufacturing and Multi-Material Structures in Sustainable Applications

1.       The manuscript text is too much.

2.       Add scale bar to Figure 1a and b. Figure 1c is not clear.

3.       Figure 2 requires labels a and b.

4.       The vertical axes in Figure 17 need a title.

 

5.       Add the scale bars to Figure 18.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 5 Report

Comments and Suggestions for Authors

The authors responded to all my previous comments, and made changes in the manuscript accordingly.

I find this version suitable for publication with one suggestion of minor change. I think Figures 6 and 7 mostly overlap in terms of content. One figure is sufficient to show how the composite specimens were designed.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 3

Reviewer 4 Report

Comments and Suggestions for Authors

Dear Authors

The manuscript in this form is acceptable.