The Role of Fibre Length on the Fatigue Failure of Injection-Moulded Composites at Elevated Temperatures under a Range of Axial Loading Conditions
Round 1
Reviewer 1 Report
The comments of jcs-1536026 were listed as follows:
(1) For all the mechanical tests, please provide the standard deviation for each data and error bar in the relevant image.
(2) The mechanical datas of pure polymer (no fillers) seem missing. It will be great if the authors can also provide them for comparison.
Thanks.
Author Response
(1) For all the mechanical tests, please provide the standard deviation for each data and error bar in the relevant image.
Author’s Response:
The standard deviation for the monotonic loading results presented in section 3.2 have been added to Table 1 and Table 2 for room temperature and 120° C. The fatigue results are presented for each experimental point and therefore no standard deviation is given. Discussion of the implications of the standard deviation for the mechanical tests has been added as follows:
“The standard deviation in properties for the test set is reported as the plus minus quantity for each value.”
“From the standard deviation it is observable that the error bars for the modulus nearly overlap, however there is a significant difference in the tensile strength.”
“The LCF material is 4.6 % stiffer than the SCF at 120 °C, however the error bars overlap each other making the modulus very similar between the two materials. The compressive strength is 6.7% higher in the LCF material than the SCF material. The margin of error for the SCF material overlaps with the margin of error for the LCF material during compressive testing and are therefore very similar. It is also noted that the standard deviation is always larger for the SCF material at 120° C.”
(2) The mechanical datas of pure polymer (no fillers) seem missing. It will be great if the authors can also provide them for comparison.
Author’s Response:
The material used in this study was provided in pellet form pre-mixed with the fibre reinforcement. Therefore, testing of the neat polymer matrix was not possible in the context of the presented study. The following sentence has been added to the materials and method section to clarify this issue.
“The fibres were premixed in the feedstock preventing testing of the neat matrix material.”
The mechanical properties provided by the material supplier have been provided for comparison to address the reviewers concern.
“For the matrix material at room temperature the stiffness is 1.54 GPa and at 120° C the stiffness is 325 MPa [35]. These values are significantly lower than the stiffnesses of the reinforced material. The room temperature strength in 60 MPa however testing at 120° C was not conducted by the supplier [35].”
Reviewer 2 Report
Dear authors
Comments:
In Fig. 3b, it is necessary to clarify which of the curves belongs to which of the two vertical axes.
It is necessary to explain how the Cumulative distribution value is calculated. How is it different from Proportion?
In the tables, it is necessary to quote the errors for the measured values.
It is necessary to comment on what is the reason for the different effect of fiber length on Elastic Modulus at room and elevated temperatures?
In Figure 6b, point the arrow cracks along the interface between the fibers and matrix. The same applies to the fiber pull out and breakage processes in Figure 6c, d.
The arguments about the development of a crack and the bridging of its surface with long fibers are generally not confirmed by the above photographs. Where, according to the authors, crack development is observed, please indicate.
Author Response
In Fig. 3b, it is necessary to clarify which of the curves belongs to which of the two vertical axes.
Author’s Response:
The following has been added to the caption to clarify the figure: “(solid (proportion), dashed (cumulative))”
It is necessary to explain how the Cumulative distribution value is calculated. How is it different from Proportion?
Author’s response:
The following has been added to the manuscript to clarify the fibre length distributions and describe how the cumulative distribution is calculated.
“The proportion represents the percentage of the fibres which have a length within the 20-micron increment for the bin. The cumulative distribution is the integration of the proportion and represents the proportion of all measured fibres under a given fibre length.”
In the tables, it is necessary to quote the errors for the measured values.
Author’s response:
The standard deviation of the experimental measurements has been added to Tables 1 and 2 as a plus, minus error value.
It is necessary to comment on what is the reason for the different effect of fiber length on Elastic Modulus at room and elevated temperatures?
Author’s response:
The modulus values are statistically indistinguishable when the standard deviation is considered although the average values have opposite trends. The following sentences have been added to the manuscript to describe this phenomenon
“From the standard deviation it is observable that the error bars for the modulus nearly overlap, however there is a significant difference in the tensile strength.”
“The LCF material is 4.6 % stiffer than the SCF at 120° C, however the error bars overlap each other making the modulus very similar between the two materials.”
In Figure 6b, point the arrow cracks along the interface between the fibers and matrix. The same applies to the fiber pull out and breakage processes in Figure 6c, d.
Author’s response:
See combined response to following comment.
The arguments about the development of a crack and the bridging of its surface with long fibers are generally not confirmed by the above photographs. Where, according to the authors, crack development is observed, please indicate.
Author’s response:
To address the reviewer’s previous two comments certain failure mode labels have been added to figures 6-9 with arrows pointing out these failure modes. This indicates how platelets form with are indicative of fibre bridging between different layers of the failure surface.
Round 2
Reviewer 1 Report
The authors addreesed my concerns.
