**5. Conclusions**

Flax fiber-reinforced composites were expected to play an increasingly important role in the design of engineering structures subject to dynamic loadings because of the requirements for lightweight, low cost, recyclability, and excellent mechanical properties. Thus, full understanding of the dynamic material behavior of FFRCs became a priority. In this study, FFRCs were fabricated by VARI. The effects of strain rate on the mechanical properties of the FFRCs were investigated using quasi-static and SHPB experiments. Distinguishing strain-hardening behaviors were observed under both quasi-static and dynamic loading conditions, which revealed that FFRCs exhibited evident strain-rate sensitivity. On the basis of the experimental results, a simplified Johnson–Cook model was obtained and verified by numerical simulation of SHPB experiments. Moreover, the dynamic behavior of the lattice structures composed of FFRCs was numerically simulated and compared with the quasi-static and drop-hammer crushing experiments. The results evidently revealed that the proposed simplified Johnson–Cook model was able to accurately describe the dynamic mechanical behaviors of the FFRC material. Overall, the results of this study could be a solid step to elucidate the dynamic mechanical behaviors of the FFRC material and could provide valuable guidance for future applications in engineering.

**Supplementary Materials:** The following are available online at http://www.mdpi.com/1996-1944/12/6/854/s1, Figure S1: Tensile stress-strain curves of pure matrix.

**Author Contributions:** Conceptualization, D.H.; Funding acquisition, D.H. and Z.Z.; Investigation, D.H., L.D., C.Z., and Z.Z.; Methodology, D.H., L.D. and C.Z.; Project administration, D.H.; Resources, D.H.; Validation, Z.Z.; Writing—original draft, D.H., and L.D.; Writing—review and editing, D.H. and Z.Z.

**Funding:** This research was funded by the National Natural Science Foundation of China [grant number: 11872100]; Joint Funds of the National Natural Science Foundation of China [grant number: U1664250]; Fundamental Research Funds for Central Public Welfare Research Institutes [grant number: 118009001000160001], Defense Industrial Technology Development Program [grant number: JCKY2018601B106], Hebei provincial major S&T Research and Development Projects [grant number: 18277610D],and Fundamental Research Funds for the Central Universities, Beihang University.

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