R-Curve Behavior of Polyhedral Oligomeric Silsesquioxane (POSS)–Epoxy Nanocomposites
Round 1
Reviewer 1 Report
This manuscript presents an interesting study using J-integral concept to quantify the initiation toughness and characterize the crack growth resistance curve. The researchers study the mechanical mechanism with the crack behavior of glycidyl POSS-epoxy composites. The experiment data conforms well with the J-integral concept as the manuscript shows. However, there is still some information which need to be supplemented for this manuscript to be accepted. I would like to give the review comment of minor revision.
1. The epoxy resins of different epoxide values have different mechanical properties due to the degree of cross linking, so the information of epoxy should also be supplemented with epoxide value.
2. The curves of figure 2 should better be marked in different colors.
3. In consideration of the best ductile performance of 5%wt. POSS-epoxy composites, the photo of ductile fracture of 5%wt. POSS-epoxy composites should also be supplemented.
4. The fracture SEM images can reflect the dispersion of filler in polymer matrix and the crack mechanism. To compare the difference of morphology of fracture comprehensively, the figure 7 should supplement the SEM images of all the levels of POSS-epoxy composites.
5. The clarification of figure 6 about the fracture behavior seems too simple without persuasion. The explanation should be improved with supplement of relative polymer physic knowledge with some reference.
Comments for author File: 
Comments.pdf
Author Response
- The epoxy resins of different epoxide values have different mechanical properties due to the degree of cross linking, so the information of epoxy should also be supplemented with epoxide value.
=> We have provided information on cross-linking.
2. The curves of figure 2 should better be marked in different colors.
=> We have uploaded a color version of the graph.
3. In consideration of the best ductile performance of 5%wt. POSS-epoxy composites, the photo of ductile fracture of 5%wt. POSS-epoxy composites should also be supplemented.
=> We have provided a reference to our previous article where we have a figure of ductile fracture at 5%
4. The fracture SEM images can reflect the dispersion of filler in polymer matrix and the crack mechanism. To compare the difference of morphology of fracture comprehensively, the figure 7 should supplement the SEM images of all the levels of POSS-epoxy composites.
=> We have provided references in our previous article where we have put SEM images at different POSS percentages.
5. The clarification of figure 6 about the fracture behavior seems too simple without persuasion. The explanation should be improved with supplement of relative polymer physic knowledge with some reference.
=> We have provided blunting and SEM of fractured images that can corroborate the physics given in figure 6.
Reviewer 2 Report
This manuscript described the characterization of R-curve behavior of POSS-Epoxy nanocomposites. There might be no critical different as compared to many previous researches regarding POSS-Epoxy nanocomposites. Also, some more experiments can be needed to verify what the authors claimed in this manuscript.
The authors should review the manuscript carefully according to the comments below.
1. At 55th line in Page 2, spelling must be checked out.
2. I think that it is better to present the figure of POSS-Epoxy nanocomposites to show how POSS is dispersed in epoxy matrix.
3. I am just wondering the trend of initiation fracture toughness is going in same way when the inclusion of POSS is more than 8 wt. %. Have you done experiment with more than 8 wt. % of POSS?
4. I am just wondering if (a) and (b) are the the same magnification in SEM image. If there is different magnification, It isn't appropriate to compare those two images.
5. There are some more SEM images to figure out the aggregation of POSS in epoxy matrix. Plus, how was the SEM images (fractured surface) of 0.5, 3, 5 wt. % POSS inclusion in epoxy matrix?
6. I think that the authors show some more experimental evidence to verify the fracture behavior as shown in Fig. 6.
Author Response
- At 55th line in Page 2, spelling must be checked out.
=> Corrected
2. I think that it is better to present the figure of POSS-Epoxy nanocomposites to show how POSS is dispersed in epoxy matrix.
=> Uploaded figure/schematic on POSS dispersion in epoxy.
3. I am just wondering the trend of initiation fracture toughness is going in same way when the inclusion of POSS is more than 8 wt. %. Have you done experiment with more than 8 wt. % of POSS?
=> We were getting asymptotic behavior after 8%, that's why we didn't add other percentages.
4. I am just wondering if (a) and (b) are the the same magnification in SEM image. If there is different magnification, It isn't appropriate to compare those two images.
=> It is the same magnification.
5. There are some more SEM images to figure out the aggregation of POSS in epoxy matrix. Plus, how was the SEM images (fractured surface) of 0.5, 3, 5 wt. % POSS inclusion in epoxy matrix?
=> We have provided a reference to our previous article that covers all percentage of POSS inclusion in the epoxy matrix.
6. I think that the authors show some more experimental evidence to verify the fracture behavior as shown in Fig. 6.
=> I believe SEM of fractured images is providing physics behind fracture. phenomena.
Reviewer 3 Report
The paper was well conducted and presented. Therefore, I would recommend the acceptance of this paper for publication in the present form.
Author Response
Thank you!
