Drilling Parameters and Post-Drilling Residual Tensile Properties of Natural-Fiber-Reinforced Composites: A Review

Round 1

Reviewer 1 Report

The article submitted by Santulli et al., entitled “Drilling parameters and post-drilling residual tensile properties of the natural fiber reinforced composites: a review” (jcs-2205167), review the effect of drilling on the mechanical properties of natural fiber reinforced composites. Although the topic is important and is suitable for the journal, however, this review article has many limitations. The academic level is relatively lacked. The significance of this review article is not enough to be published. This reviewer feel very sorry that he cannot recommend its publication in present form. 

Author Response

We considerably modified the paper, adding information about alternative methods for drilling, fatigue testing, and rearranging it in order to better suit the topic developed. I hope this can satisfy the reviewer. 

Reviewer 2 Report

The manuscript has given a critical review on the influence of drilling parameters on the defects formation and residual tensile properties of natural fiber reinforced composites. There are some suggestions can be considered:

(1) The manuscript mainly described the suitable machining parameters of mechanical drilling process for the natural fiber reinforced composites, while, the non-traditional machining methods, such as laser drilling, ultrasonic vibration assisted drilling, and water jet drilling, may also have advantage to process the composite materials. Therefore, some discussion could be added about the non-traditional machining.

(2) In addition to the residual tensile properties, the fatigue resistance changes of the machined natural fiber reinforced composites are also important. Is there any literature about the fatigue resistance of the composite materials after drilling?

(3) The resolution of the figures can be improved.

Author Response

1. Some discussion about the non-traditional machining has been added, although it is fair to say that the work carried out so far on natural fiber composites in this domain is limited. What exists has been reported to the best of our knowledge anyway.
2. There is very little literature on post-drilling fatigue of natural fiber composites and it has also been reported in a separate Section 4.
3. The resolution of figures has been checked and improved when necessary (please note that some figures were added, and Figure 5 was deleted as not much resolved and fairly irrelevant in the end).

Reviewer 3 Report

This paper reviewed drilling parameters and residual tensile behavior of nature fiber-reinforced composites. Overall, I strongly suggest that authors should spend more time thinking how to address different drilling parameters and tools causing damage and affecting residual behavior of nature-fiber-reinforced composites. This is very weak spot in particular for Section 3 in this review paper since the title is highlighting the drilling.

For example, in Section 3, authors talked about 4 aspects (notch, hybrid fibers, nanofillers, and surface treatment) affecting the residual strength of nature fiber-reinforced composites. However, the importance of the drilling parameters and tools was not mentioned. Authors should correlate different drilling parameters with the residual strength due to the foregoing 4 aspects. Related figures should also be included rather than Figures 3 and 5. Also, a comparison with carbon-/glass-fiber-reinforced polymers will even strengthen this paper. In this way, it will be more useful for readers.

In addtion, I also suggest authors to include how the drilling parameters and tools affect the fatigue behavior of nature fiber-reinforced composites. This is important since the sub-critical damage induced by drilling can have more effects on slow propgation of damage in composites in fatigue.

In Section 2, I will suggest authors to rearrange the sections. Authors talked about how the damage (matrix, delamination, fiber) was caused by different drilling parameters (e.g., feed rate, spindle speed, etc.) in Section 2.3 and drill geometery and materials in Section 2.4. Those are good. But the delaminiation factor (Section 2.1) should not be a sinlge section, which should be moved to Sections 2.3 and 2.4. Authors can talk about how drilling paramters, drill geometry, and drill materials affect delalmiantion in composites in Sections 2.3 and 2.4.

To summerize the results in Section 2, authors can have a table briefly describing different levels of damage due to different processing and tooling paramters as authors show in Figure1. Authors also should have more discussions on the difference of drilling-induced damage between carbon-/glass-fiber-reinforced polymers and nature fiber composites. This will be very beneficial to readers. Finally, in Section 2. after talking the influence of drilling on damage in composites, then authors can talk about Section 2.2 for how to control and minimize the force, torque, and tool wear to mitigate the damage in composites due to drilling.

In conclusion, again, authors should focus more on drilling. How different drilling procedures affect damage and residual behavior of nature-fiber-based-composites.

Author Response

We tried to concentrate on drilling parameters. A new Table 1 was added and the paper was fully rearranged. Some of the figures were added, which indicate the drilling performance in practice. Figure 5 was also deleted. The other figures (3 and 4) were not deleted as this was not asked by the other reviewers, hence would have impaired the paper.

The literature search has been extended to new works and to some relevant topics (non-conventional drilling, post-drilling fatigue). 

Hope this suits your requests.

Round 2

Reviewer 2 Report

The manuscript can be accepted in present form.

Reviewer 3 Report

I am okay with the modified version.