**5. Conclusions**

In this paper, tensile tests, nanoindentation tests, and lapping experiments were carried out on five varieties of PEEK and its fiber-reinforced materials. The influences of the types and mass fraction of the modified fibers on the material properties were investigated in this work, including tensile strength, hardness, modulus, and lapping machinability. The following conclusions have been drawn from the results.


**Author Contributions:** Conceptualization, S.G. and R.K.; methodology, S.G. and J.Q.; software, J.Q. and H.L.; investigation, S.G. and J.Q.; data curation, J.Q.; writing—original draft preparation, S.G.; writing—review and editing, H.L. and J.Q.; visualization, J.Q. and H.L.; supervision, R.K.; funding acquisition, S.G. and R.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was financially supported by the National Natural Science Foundation of China (51975091, 51991372, 51735004), the National Key Research and Development Program of China (2018YFB1201804-1), and the Lab of Space Optoelectronic Measurement and Perception (LabSOMP-2019-05).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author.

**Acknowledgments:** The authors would like to acknowledge the financial support from the National Natural Science Foundation of China, the National Key Research and Development Program of China and the Lab of Space Optoelectronic Measurement and Perception.

**Conflicts of Interest:** The authors declare no conflict of interest.
