Bending Performance of Plantation Teakwood and Its Mechanism Based on Radial and Tangential Directions
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Author
Suggestions and comments are describe in attached file
Best regards
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 1 Comments
Point 1: First of all you should change in the manuscript word „chordal” to „tangential” – this is a typical term for direction perpendicular to the radial direction in cross-section of wood.
Response 1:
I am really sorry for the mistakes due to our negligence. We have corrected them in the manuscript.
Point 2: Please add some information about the time when first time bending the solid wood to furniture production take place.
Response 2:
According to the reviewers' suggestions, we supplement relevant references in the introduction. The content is: “As early as the 1830s, the German furniture manufacturer Michael Thonet adopted the hydrothermal treatment technology, successfully softened beech wood, and then bent it into various furniture bending components, and made a series of creative bentwood furniture [5]. With the development of science and technology, researchers deeply explored bending species and softening technology of solid wood and achieved significant results.”
Point 3: Add one paragraph with information of “modification“ the bending process: what kind of techniques or chemicals where used to softening the wood.
Response 3:
Thanks to the reviewers’ suggestions. There is no information on the improvement of the bending process in the introduction mainly because (1) this manuscript is one of a series of research results on teakwood softening bending technology, which focuses on the bending mechanism of teakwood; (2) the authors have already published a paper on the teakwood softening process in Forests with the title "Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution" ( Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773), which mainly researches the softening process of teakwood, and the research progress of the softening process has been described in the introduction; (3) The series of research results mainly includes three parts: the softening process, the bending properties and mechanism, and the drying and shaping technology. There are 3 papers in total. This manuscript is the second one.
Point 4: Where the bending wood are used nowadays.
Response 4:
The bent wood is mainly used in various fields such as furniture and construction.
Point 5: I cant’t find justification for using teak wood to bending process (there are many different species and China is not typical environment for teak cultivation.
Response 5:
(1) This study is based on the National Key Research and Development Program project "Research on Integration and Demonstration of Furniture Manufacturing Technology of Precious Tree Species".
(2) Research on the wood properties of teakwood can improve its application range and added value.
(3) China does not have natural forest teak, in the 1960s, the teak was introduced and planted in many provinces, such as Yunnan, Hainan, Guangdong, Guangxi, Fujian, Sichuan, etc. Now the afforestation area is about 35,000 hectares.
Point 6: In my opinion there is lack information in point 2.3.2. I can’t repeat your experiment. I don’t know nothing about time, temperature of recation, how you prepare the solvent, how many samples were you used, density of the wood before and after experiment, parameters of heating the wood with steam in reactor.
Response 6:
(1) According to the reviewer's suggestion, we supplemented some content in 2.3.2. The specific content is: "Based on the previous study, we made teakwood bending specimens by adopting the better softening process parameters (softening temperature was 125°C, softening time was 175 min, and softening solution concentration was 15%) and by bending method of applying a steel strip on the convex side of the softened wood [10]."
(2) This paper is based on the previous paper (Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution(Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773)" to further investigate the bending mechanism of teakwood and its softening process parameters are consistent with the previous paper.
Point 7: What about statistical analysis – no information.
Response 7:
The authors in "Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution (Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773)," a detailed statistical analysis of the experimental data of the softening process has been carried out. This manuscript focuses on mechanical relationships and micro-morphology to reveal the bending mechanism of teakwood.
Point 8: During the bending process did you use the belt ??? (typical technology used the metal bend. I can’t find any information about this.
Response 8:
According to the reviewers' suggestion, we added some content in 2.3.2. The specific content is: "Based on the previous study, we made teakwood bending specimens by adopting the better softening process parameters (softening temperature was 125°C, softening time was 175 min, and softening solution concentration was 15%) and by bending method of applying a steel strip on the convex side of the softened wood [10]."
Point 9: samples to SEM and AFM analysis – from which point of samples they were collected– middle of sample, end, upper surfece, lower surface?
Response 9:
(1) According to the reviewer's suggestion, we added the main content in 2.4.1. The specific content is: "Small samples were taken from the maximum bend in the middle of the teakwood bending specimen, with a size of 10 × 10 × 5 mm, and the micro-morphological changes of the cell wall in the two bending states were observed by using an ambient scanning electron microscope (SEM) (Sigma300, Germany)."
"The weak-phase structure of teakwood was studied by atomic force microscopy (AFM) when tiny cracks sprouted in the cross-section of the cell wall between the tensile side and the neutral layer after bending, to analyze the change rule of the cellular morphology of teakwood when it reaches the minimum bending radius."
(2) In analyzing Figures 9 and 10, the specific collection points on the tensile and compressive sides at the maximum bending of the specimen were indicated in detail.
(3) When analyzing Figures 11 and 12, there are specific instructions for the location of the acquisition set for the images.
Point 10: Please clarify marks from equation 1 and 2 and add them to table 1 and 2 and figure 3 and 5.
Response 10:
According to the the reviewers’ suggestion, we have added the markers in Equation 2 to Tables 1 and 2 and Figures 3 and 5. The marks in Equation 1 are too cumbersome when added together with the unit (mm), and only the unit (mm) has been retained.
Point 11: Please change the color of text in the figure 8 and 9 (not readable for reader).
Response 11:
Based on the reviewer's suggestions, we have modified the color of the text in Figures.
Point 12: Fig 4 there were used the same conditions for samples from this picture?
Response 12:
Figure 4 shows a picture of teakwood's susceptibility to bending and breaking under a single steam condition. The same softening treatment conditions were used for all three pictures.
Point 13: Fig 2 Add to the figure („h” is always a high of sample or this parameter describe dimension in radial or tangential direction.)
Response 13:
According to the reviewers’ suggestion, we have added the specimen's height identifier "h" to Figure 2.
Point 14: „r” from figure 2 are the same what „R” from equation 2 please clarify.
Response 14:
I'm so sorry for that. We've standardized the "R" in the picture and the formula.
Point 15: Authors very good describes theirs results. Unfortunately in this paragraph is lack of statistical analysis, density changes and lack informations about type of destruction the samples after bending proces.
Response 15:
The authors have analyzed the experimental data of the softening process in detail and statistically in the paper entitled "Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution(Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773)". This manuscript focuses on mechanical relationships and micro-morphology to reveal the bending mechanism of teakwood.
Point 16: I’m interesting also how change the chemical composition after the treatment the teak samples by Triethanolamine and is that influence on bending process?
Response 16:
The authors have discussed in detail the changes in chemical constituents of teakwood samples after treatment with triethanolamine in the paper entitled "Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution (Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773)". This manuscript focuses on revealing the bending mechanism of teakwood in terms of mechanical relationships and micro-morphology.
Reviewer 2 Report
Comments and Suggestions for Authors1. Kindly include the image for chordal bending too as shown in figure 4 for radial bending.
2. Technically discuss further about, why the damage occurs in the way it is shown in the image, do not give the generic reasons.
3. Why impregnated wood bending radius (mm) is lesser than unimpregnated wood as shown in the graph (figure 3), whereas bending coefficient is higher?
4. Why impregnated wood bending radius (mm) is lesser than unimpregnated wood as shown in the graph (figure 5), whereas bending coefficient is higher?
5. Is there localized fracture in the impregnated wood also? As seen near 40 mm in the graph (figure 6), please provide the reason.
6. In chordal bending (figure 7) localized fracture is more around 70 to 80 mm, give reason for it.
7. State the inference for figure 8 and 9, why such a deformation occur.
8. Discuss, why micro crack is seen in the radial bending?
9. Discuss, why parenchyma cell crack is seen in the chordal bending?
Comments on the Quality of English LanguageEnglish can be improved for better understanding.
Author Response
Response to Reviewer 2 Comments
Point 1: Kindly include the image for chordal bending too as shown in figure 4 for radial bending.
Response 1:
According to the reviewers’ suggestions, we have added Figure 6 with a text description.
Point 2: Technically discuss further about, why the damage occurs in the way it is shown in the image, do not give the generic reasons.
Response 2:
According to the reviewers’ suggestions, we have made appropriate additions to the contents of the manuscript. The specific content is: "During bending of wood, the compressive deformation ability of the concave side is greater than the tensile deformation ability of the convex side, and the middle region of the tensile side of the convex side is subjected to the maximum tensile stress and tensile deformation, and the tensile side of the specimen will be damaged when it is increased to the limiting value."
Point 3: Why impregnated wood bending radius (mm) is lesser than unimpregnated wood as shown in the graph (figure 3), whereas bending coefficient is higher?
Response 3:
The bending radius (mm) of the impregnated wood is smaller than that of the unimpregnated wood, indicating that the bending properties of teakwood are improved after impregnation and a greater degree of bending can be realized. According to equation 2, the smaller the bending radius, the greater the value of the bending coefficient and the better the bending performance for the same thickness (h) of teakwood.
Point 4: Why impregnated wood bending radius (mm) is lesser than unimpregnated wood as shown in the graph (figure 5), whereas bending coefficient is higher?
Response 4:
The reason is the same as (3).
Point 5: Is there localized fracture in the impregnated wood also? As seen near 40 mm in the graph (figure 6), please provide the reason?
Response 5:
(1) Some minor cracks do occur in impregnated wood during bending. The results of our supplementary tests show that some cracking phenomenon occurs occasionally, mainly in the area of the junction between the radial and tangential sections (on the tensile side), but it does not affect the later processing and utilization.
(2) This phenomenon is mainly attributed to two reasons: firstly, the wood fibers at the junction have a weakened ability to interconnect under softening conditions, which increases the risk of cracking; secondly, the stress concentration effect at the junction can produce small cracks but generally does not result in bending fracture.
Point 6: In chordal bending (figure 7) localized fracture is more around 70 to 80 mm, give reason for it.
Response 6:
It can be seen from Figure 7 that in the interval of 70-80 mm, the teakwood is in the transition from the elastic-plastic deformation stage to the plastic deformation stage. This transition stage requires greater loads to increase the magnitude of the deformation of teakwood. As the load increases, the bending surface of the wood is perpendicular to the annual rings, which makes it easy to lose bending stability under external forces, leading to localized fracture.
Point 7: State the inference for figure 8 and 9, why such a deformation occur.
Response 7:
(1) In lines 295-307 and 321-330 of the manuscript, Figures 9 and 10 are explained and illustrated, respectively.
(2) The specific content is: "Figure 9 shows the SEM images of teakwood during the stretching and compression of the wood cell walls before and after radial bending. The radial section images of the material showed that the conduits and pit of teakwood were rounded, the ray parenchyma was mottled, and their cellular organization was more obvious and interwoven with the wood fibers (Figure 9a-c). After radial bending, teakwood showed a greater degree of tensile deformation on the tensile surface of the outer side of the radial section (Figure 9d-e), while on the compression surface in the middle of the inner side of the bending surface, the cell wall showed multilayered folds (Figure 9f-g), and uniformly dispersed fine folds could also be seen the macroscopic features with the naked eye. Meanwhile, the innermost tangential section (concave surface) of teakwood undergoes the greatest compressive deformation, as seen through Figure 9h-i, where compressive misalignment occurs at the junction of the ducts and the ray parenchyma, mainly to meet the demands of the bending deformation of teakwood."
"Figure 10 shows the SEM images of teakwood during the stretching and compression of cell walls in the tangential section of teakwood after tangential bending. It can be seen from the images that the ray parenchyma of the tangential section of the bending specimen sprouted smaller cracks at the junction with the wood fiber. The wood rays are all composed of thin-walled cells with lower tensile strength and poorer mechanical properties, which are prone to fracture from the ray parenchyma during bending and stretching (Figure 10a-b), thus affecting the bending properties of the wood [43,44]. In the tangential section on the compression side, there are more earlywood zones, which make the inner side have a relatively strong compression defor-mation ability along the grain (Figure 10c-d)."
Point 8: Discuss, why micro crack is seen in the radial bending?
Response 8:
AFM morphology analysis reveals that teakwood has a weak phase structure when cracks sprout in the cell wall cross-section between the tensile and neutral layers after bending. In lines 339-342 of the manuscript, the reason for the emergence of microcracks in radial bending is elucidated. The specific content is: " This is mainly because, under bending load, the outermost tensile side of the bending specimen of teakwood undergoes the maximum parallel to grain tensile stress, which tends to crack the S2 layer of the secondary wall, and the transverse shear stress tends to debond the S1 and S2 layers."
Point 9: Discuss, why parenchyma cell crack is seen in the chordal bending?
Response 9:
This phenomenon is attributed to the fact that wood rays, which are mainly composed of ray parenchyma, are subjected to lower tensile strengths and poorer mechanical properties, and are prone to fracture during bending and stretching starting from the ray parenchyma, thus affecting the bending properties of the wood. The generation of cracks in the ray parenchyma is described in manuscripts 324-327 and 355-360.
Reviewer 3 Report
Comments and Suggestions for AuthorsIn the methodology, item 2.1, the authors could explain what the chemical products were used for.
In item 2.2, I consider it important to include some images of the equipment used in the research.
In item 2.3.2, the authors should better describe the process for impregnating the softening substances, in what proportions they were used, for how long... Was the methodology followed by any standard?
Author Response
Response to Reviewer 3 Comments
Point 1: In the methodology, item 2.1, the authors could explain what the chemical products were used for.
Response 1:
(1) Based on the reviewers' suggestion, we have added the use of chemical products in item 2.1 of our manuscript. The specific content is: "The softening solution triethanolamine (TEA, C6H15NO3), penetrant sodium chloride (NaCl, AR), and surfactant sodium dodecylbenzene sulfonate (SDBS, C18H29NaO3S,) were purchased from Shanghai Sinopharm Group Chemical Reagent Co."
(2) The mechanistic interaction of chemical products with wood has been studied in depth in another article, "Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution (Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773) ". In this manuscript, the uses of the chemical products are only described generally.
Point 2: In item 2.2, I consider it important to include some images of the equipment used in the research.
Response 2:
Based on the reviewers' suggestion, we uploaded pictures of the main equipment in the "Supplementary File(s)". The pictures of the equipment were not good enough, so they were not added to the manuscript.
Point 3: In item 2.3.2, the authors should better describe the process for impregnating the softening substances, in what proportions they were used, for how long... Was the methodology followed by any standard?
Response 3:
(1) According to the reviewer's suggestion, we supplemented the softening process parameters in item 2.3.2. The contents are as follows: " Based on the previous study, we made teakwood bending specimens by adopting the better softening process parameters (softening temperature was 125°C, softening time was 175 min, and softening solution concentration was 15%) and by bending method of applying a steel strip on the convex side of the softened wood (Yao, L.; Ji, L.; Sun, D.; Wang, Z.; Ge, H.; Xu, M.; Yu, M. Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution. Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773)".
(2) This manuscript is an in-depth study of softening process based on the article "Preparation of Teakwood Bending Components with Excellent Softening Properties by Vacuum Impregnation with Triethanolamine Compounding Solution" (Forests 2023, 14, 1773. https://doi.org/10.3390/f14091773) , therefore the process for the preparation of the specimens is only described generally.
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsI accept all your answer on my review report
