Experimental Analysis of Heat-Affected Zone (HAZ) in Laser Cutting of Sugar Palm Fiber Reinforced Unsaturated Polyester Composites

Round 1

Reviewer 1 Report

Reviewers' comments:

Full Title: Experimental Analysis of Heat-Affected Zone (HAZ) in Laser Cutting of Sugar Palm Fiber Reinforced Unsaturated Polyester Composites.

Comments: 
The manuscript reported on Experimental Analysis of Heat-Affected Zone (HAZ) in Laser Cutting of Sugar Palm Fiber Reinforced Unsaturated Polyester Composites. The manuscript needs a detailed editing. The authors need to provide answers to the issues listed below before the manuscript should be accepted for publication.

- What is the aspect ratio of the fibres?

- Why basalt fibres are chosen? What about the cost benefit ratio?

- How the fibres length of 24 mm can be accommodated 15 mm thickness slab?

- Why geo polymer mortar was chosen instead of cement mortar?

- What source material has been used in geo mortar?

- Line number 223 - plate using CO2 laser….to……plate using CO₂ laser.

- Line number 249 - were ranked 2nd and 3rd, respectively……..to ………..were ranked 2^nd and 3^rd, respectively.

- Figures 6 and 7 – not clear make clear.

- What about the curing of geo mortar? Ambient curing or steam curing?

- How the bonding between geo mortar and fibres are ensured?

- For what application these composites are recommended?

- What about the frost and fire resistance of this composite and fibre?

- Some sentences need reconstruction and the level of English should be improved.

Author Response

Dear sir: It gives us great pleasure to receive your valuable comments on my research paper which is being reviewed by you. We also thank you for your comments and guidance which greatly contributed to improving our research paper. We are also pleased to provide you with our answers to all your comments.   Point 1: What is the aspect ratio of the fibers? Response 1: Aspect ratio was added in section 2.1 as you recommended.   Point2: Why basalt fibers are chosen? What about the cost benefit ratio?  Response2: The chosen fiber was sugar palm fiber because it sowed good mechanical and physical properties as it was referred in section 1. And it is very cheap renewable material.   Point 3:How the fibers length of 24 mm can be accommodated 15 mm thickness slab? Response3: The fiber length is about 5 to 10 mm and the manufacturing method was hand- lay-up which allow to use long fibers with thin plates. we used three different thicknesses in the experiments 2,4, and 6 mm  

Point4: Why geo polymer mortar was chosen instead of cement mortar?

Response4:The matrices was used in this experimental study was unsaturated polyester because its composites showed good properties as it was referred in section 1.

Point5: What source material has been used in geo mortar?

Response5: In this research the material was a sugar palm fiber reinforced unsaturated polyester. Sugar palm fiber is extracted from local tree that grows in tropical forests in South-East Asia.

Point6: Line number 223 - plate using CO2 laser….to……plate using CO₂ laser.

Response6: The Correction has been done.

Point7- Line number 249 - were ranked 2nd and 3rd, respectively……..to ………..were ranked 2^nd and 3^rd, respectively.

Response7: The Correction has been done.

Point8: Figures 6 and 7 – not clear make clear.

Response8: The Corrections have been done and they replaced with clear figures

Point9: What about the curing of geo mortar? Ambient curing or steam curing?

Response9: The material that was tested in this study was Sugar Palm Fiber Reinforced Unsaturated Polyester Composite (SPF-UPE) and all of needed the treatments were explained in section 2.1 

Point10: How the bonding between geo mortar and fibers are ensured?

Response10: In this research; Sugar Palm Fiber Reinforced Unsaturated Polyester Composite (SPF-UPE) was used as tested material and it showed good physical and mechanical properties as it was referred in the study so the bounding between fibers and polymer is good as the previous studies found.    

Point11: For what application these composites are recommended?

Response11: Some explanations about recommended application were added in section 1(introduction) as you recommended. 

Point12: What about the frost and fire resistance of this composite and fiber?

Response12: Based on our knowledge, no study has been conducted on Sugar Palm Fiber Reinforced Unsaturated Polyester Composite (SPF-UPE) specifically related to frost and fire resistance, but in the future, studies can be conducted in this field based on the treatments that were carried out on polyester-based composites.

Point13: Some sentences need reconstruction and the level of English should be improved.

Response13: The paper will be sent to  MDPI English Editing Services for proofreading.

Finally, thanks again for your valuable and considerate comments that will improve our research. Thank you very much. Sincerely.

Reviewer 2 Report

In this manuscript, the effects of processing input parameters on the heat-affected zone (HAZ) of three different material thicknesses of sugar palm fiber reinforced unsaturated polyester composites (SPF-UPE) cut with a CO2 laser was studied. Laser power, traverse speed and gas pressure were selected as the most influential input parameters on HAZ to optimize the HAZ response with fixing all the other input parameters. Taguchi's method was used to determine the levels of parameters that give the best response to HAZ. The significance of input parameters was determined by calculating the max-min variance of the average of S/N ratio for each parameter. Analysis of variation (ANOVA) was used to determine of each input parameter's contribution to the influence on the HAZ depth. I am pleased to send you moderate comments. The results and theme of this paper is quite interesting. The layout is clear and easy to understand. Generally, this manuscript makes fair impression and my recommendation is that it merits publication in this Journal, after the following major revision:

1. The authors need to reorganize the current introduction, which normally consists of three parts at least: background, literature review, brief of the proposed work. The current one is nothing but a literature review. Why their work is important comparing to previous reports? I think this is essential to keep the interest of the reader.
2. The authors should give some detailed description of the experiments such as Composite Forming, Experimental Setup, Cutting Parameters Selection, HAZ measurement, etc.
3. In Table 4, 5, 7, 8, 10, 11, 12, the authors should give the explanations for the difference of data collected from different sources.
4. The general results showed that the minimum levels of laser power and the highest levels of traverse speed and gas pressure gave the optimum response to HAZ. Gas pressure had the most significant effect on HAZ with contribution decreases as the material thick ness increased, followed by the traverse speed with contribution increases with the increase in the material thickness. Laser power came third with a small contribution to the effect on HAZ, and it did not show a clear relationship with the change of the material thickness. The authors should explain this point.

5. Fiber reinforced polymer composite including fibrous porous media has been widely used in many fields of life. The present work mainly focuses on lab work. It does not necessarily imply that the theoretic work (modeling) is not important. The authors omit this part during the current literature review, which should include a brief review of the theoretic work after revision. In the theoretic perspective, fractal theory is a very important tool, which can investigate physical properties of fibrous porous media (see [A fractal model for capillary flow through a single tortuous capillary with roughened surfaces in fibrous porous media, Fractals, 2021, 28(4):2150017; International Journal of Heat and Mass Transfer, 2019, 137:365-371]). Authors should introduce some related knowledge to readers.
6. At last, the English writing needs improving.

Author Response

Dear sir:

It gives us great pleasure to receive your valuable comments on my research paper which is being reviewed by you. We also thank you for your comments and guidance which greatly contributed to improving our research paper. We are also pleased to provide you with our answers to all your comments.

Point 1: The authors need to reorganize the current introduction, which normally consists of three parts at least: background, literature review, brief of the proposed work. The current one is nothing but a literature review. Why their work is important comparing to previous reports? I think this is essential to keep the interest of the reader.

Response1: Important details to cover the deficiencies in this aspect have been added to the introduction based on your recommendation.

Point 2: The authors should give some detailed description of the experiments such as Composite Forming, Experimental Setup, Cutting Parameters Selection, HAZ measurement, etc.

Response 2: In section 2.1, the composite, its components, the type of fibers, and all the primary and chemical treatment processes that were carried out were clarified. This is in addition to clarifying the type of manufacturing process, the dimensions of specimens and molds, and setup and disassembly of molds.

In second 2.2, an explanation is given about the data of the laser machine used and the type of the laser and experiment data, in addition to all the fixed and variable parameters in this experiment.

In section 2.3, the methodology for selecting the input processing parameters and their levels was presented, along with the justifications for choosing the parameters and the justifications for excluding the excluded values, supported by the illustration figures.

In section 2.4, the measurement methodology used to measure HAZ is explained in addition to the data of the devices that were used for this purpose, supported by the illustration figures. This is in addition to providing a detailed explanation of the optimization method and the statistical methods used in section 2.5.

The authors are ready to accept your valuable advice in particular.

Point 3: In Table 4, 5, 7, 8, 10, 11, 12, the authors should give the explanations for the difference of data collected from different sources.

Response 3: Although the study aims mainly to obtain experimental results in order to be applied when performing the LBM cutting process for the composites, some clarifications have been presented in the last paragraph of section 3 (Results and Discussion) that explains this difference in data such as the justification we have provided for the decline in the importance of gas pressure with increasing the thickness of the material, so we believe that it may be a result of a reduction in the gas flow rate due to the effect of friction at the boundary layer along the passing area of the flow through the kerf, which increases with the thickness of the material. This is in addition to other clarifications discussed in this section.

Point 4: The general results showed that the minimum levels of laser power and the highest levels of traverse speed and gas pressure gave the optimum response to HAZ. Gas pressure had the most significant effect on HAZ with contribution decreases as the material thick ness increased, followed by the traverse speed with contribution increases with the increase in the material thickness. Laser power came third with a small contribution to the effect on HAZ, and it did not show a clear relationship with the change of the material thickness. The authors should explain this point.

Response 4: These results have been clarified in the section 3, the most important of which is the increase in the effects of the boundary layer with the increase in the material thickness, which affects the gas flow rate locally at the kerf and thus affects the rate of cooling which effects the HAZ. Also, the effect of the increase of traverse speed, which reduces the time period during which the material is exposed to the heat produced by the laser, which is reflected positively on HAZ. This is in addition to recording all available observations of the process response to the change of cutting parameters.

Point 5: Fiber reinforced polymer composite including fibrous porous media has been widely used in many fields of life. The present work mainly focuses on lab work. It does not necessarily imply that the theoretic work (modeling) is not important. The authors omit this part during the current literature review, which should include a brief review of the theoretic work after revision. In the theoretic perspective, fractal theory is a very important tool, which can investigate physical properties of fibrous porous media (see [A fractal model for capillary flow through a single tortuous capillary with roughened surfaces in fibrous porous media, Fractals, 2021, 28(4):2150017; International Journal of Heat and Mass Transfer, 2019, 137:365-371]). Authors should introduce some related knowledge to readers

Response 5: In fact, we acknowledge the importance of theoretical analysis when studying the properties, applications, and processing of natural fiber composites, but as we indicated in the introduction that the studies conducted on natural fiber composites cut by LBM technology is very limited. This is for natural fiber compounds in general, where for the composite that we conducted the study on, according to our knowledge, there is no study conducted on it in the field of cutting by unconventional methods, although there are a considerable number of studies on this material related to the physical and mechanical properties and ways to improve them by optimizing processing and manufacturing methods and control its components. This lack of studies related to cutting natural composites by LBM technology made the study seem as if it did not provide sufficient literature review, while the truth is that there is a shortage of studies that dealt with this field whether theoretically or experimentally.

Point 6: At last, the English writing needs improving.

Response 6: The paper will be sent to MDPI English Editing Services for proofreading

Finally, thanks again for your valuable and considerate comments that will improve our research. Thank you very much. Sincerely.