Residual Stress Evolution of Graphene-Reinforced AA2195 (Aluminum–Lithium) Composite for Aerospace Structural Hydrogen Fuel Tank Application
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsThis work focused on the residual stress evolution of graphene-reinforced AA2195 (Aluminum-Lithium) composite for aerospace structural hydrogen fuel tank application. The topic is meaningful and some good results were obtained. However, the authors should address the following issues before this paper is accepted for publication in Journal of composites Science.
(1) In page 3, “Fig. 5.21(b)” should be “Fig. 2.1(b)”.
(2) Please check if Fig. 3.3 (-32 MPa) and Fig. 3.4 (-31 MPa) are reversed?
(3) Why is there a significant increase of residual compressive stress (-68 MPa) after the fourth pass of hot rolling?
(4) When analyzing the evolution mechanism of residual stress, please provide corresponding experimental or simulation evidence.
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Reviewer 2 Report
Comments and Suggestions for AuthorsThe manuscript titled “Residual Stress Evolution of Graphene-Reinforced AA2195 (Aluminum-Lithium) Composite for Aerospace Structural Hydrogen fuel tank Application” is an intriguing study fit for publication in J. Compos. Sci., but the following comments need to be addressed before publication:
- In the Abstract section, while numerical stress values are provided, the percentage improvements or comparisons with unreinforced AA2195 are only mentioned briefly. Can the authors explicitly quantify the enhancement in residual stress retention compared to the unreinforced alloy for clarity?
- In the introduction section, Have the authors conducted any preliminary trials or literature survey beyond Ref. [7,8] that validate this threshold in the specific context of squeeze casting and AA2195?
- Hydrogen fuel tank applications are mentioned in the title but not elaborated upon in the introduction.Could the authors clarify how the findings relate to service conditions of hydrogen fuel tanks (e.g., cyclic loading, cryogenic temperatures)?
- In the hot rolling process, Reheating temperature (480 °C), rolling force, and speed are well documented.How was the reheating temperature between passes (480 °C) selected? Was it experimentally validated for optimal grain structure and minimal stress buildup?
- How many measurement replicates were conducted per sample? Were standard deviations or confidence intervals calculated?
- The authors attribute the observed tensile residual stress in the unreinforced AA2195 alloy to quenching effects during the T8 heat treatment. However, it is unclear whether this measurement is based on a single data point or averaged over multiple samples. Can the authors clarify the measurement methodology, provide any statistical error (e.g., standard deviation), and discuss the representativeness of this value?
- The transition from tensile to compressive residual stress upon graphene addition is well noted and attributed to thermal expansion mismatch and graphene-induced dislocation pinning. However, to strengthen this claim, can the authors provide microstructural evidence (e.g., SEM/TEM images or EDS mapping) showing uniform graphene dispersion?
- In fourth pass hot rolling, Why is there a sudden jump in stress at the fourth pass compared to previous gradual changes?
- How does solution treatment affect microstructure, and are mechanical properties post-treatment reported in the fifth pass cold rolling?
Author Response
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Reviewer 3 Report
Comments and Suggestions for AuthorsThe subject of your study is timely and relevant, and I appreciate your efforts in addressing residual stress behavior in graphene-reinforced Al–Li alloys. However, after a detailed evaluation, I regret to inform you that I am unable to recommend the manuscript for publication in its current form.
The manuscript lacks critical experimental validation—particularly in terms of mechanical property measurements and comprehensive microstructural analysis—which are essential to fully support the conclusions. Additionally, the discussion is often repetitive, and the novelty is somewhat limited without broader comparative data or deeper insights.
I appreciate your work and encourage you to further strengthen the manuscript for possible submission elsewhere.
1) While the paper focuses on residual stress evolution, no mechanical properties (tensile strength, yield strength, hardness, fatigue) are presented to correlate the effect of stress states on performance.
2) The only microstructural characterization seems to be EDS and elemental mapping. No optical microscopy, SEM, or TEM images of grain structure, dislocation density, or precipitate morphology are provided.
3) The paper acknowledges that only surface-level residual stresses were measured. However, no discussion is provided about how this limitation may affect interpretation, especially since internal stresses in rolled/aged materials can be significantly different.
4)The text is overly verbose and often repeats the same explanations across sections. For example, the role of graphene as a dislocation barrier is mentioned almost identically in all residual stress discussion subsections.
5)The study would benefit from comparing its findings to similar studies (e.g., other AA2xxx alloys with/without graphene or other reinforcements).
6)Although the paper claims that 0.5 wt.% graphene is optimal, no reference is given to support this selection with direct comparative data or prior studies in AA2195
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Round 2
Reviewer 3 Report
Comments and Suggestions for Authors1) The phases shown as graphene in Figure 3a cannot be graphene; it is not possible to show graphene, which should be nano-sized, in this way. It may be visible at larger magnifications.
In Figure 3b, the peaks of the elements are not visible and the table is not readable. In addition, the elemental mapping in Figure 3 is not clear, it is not possible to understand which phase is in which region from this map.
2)The same applies to Figure 4 as Figure 3.
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