**6. Conclusions**

In this work, a VAM-based reduced-order plate model was established to analyze the effective performance of the orthogrid-stiffened FRP panel (OSFP). The influences of the material and structural parameters of the OSFP were investigated by parametric studies, and the following conclusions were drawn.

(1) The results of static displacement, local field distributions, natural frequencies and buckling loads predicted by 2D-RPM were consistent with those of 3D FE model, but the computational efficiency was greatly improved, which verifies the accuracy and effectiveness of the VAM-based reduced-order plate model.

(2) The equivalent stiffness increased gradually with increasing stiffener thickness or height and decreasing length–width ratio or periodic length. The influences of the structural parameters on the buckling load were closely related to the equivalent stiffness. The effect of the stiffener height on the natural frequency of the OSFP was much greater than those of the other structural parameters.

(3) Different layup configurations had significant influences on the equivalent stiffness and buckling load of the OSFP, while they had little effect on the vibration modes. With the increase in the 0◦ ply ratio, the equivalent stiffness in the fiber direction increased significantly, and the first buckling load and natural frequency increased gradually. The static displacement and vibration modes of the orthogrid-stiffened FRP panel were different from those of the blade- and T-stiffened FRP panels, indicating that the vibration modes of the stiffened FRP panel could be varied by adjusting the stiffening forms.

**Author Contributions:** Conceptualization, P.W. and Y.Z.; methodology, Y.Z.; software, Z.S.; validation, D.L. and Q.Y.; formal analysis, P.W.; investigation, D.L.; resources, Q.Y.; data curation, Z.S.; writing-original draft preparation, P.W.; writing-review and editing, Y.Z. and Z.S.; visualization, Q.Y.; supervision, Y.Z.; project administration, D.L.; funding acquisition, Y.Z. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the National Natural Science Foundation of China (Grant/Award Numbers: 51778088, 52073036).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data available on request due to restrictions, e.g., privacy or ethical. The data presented in this study are available on request from the corresponding author. The data are not publicly available due to subsequent analyzes and publications.

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

#### **References**

