# The Effect of Inflatable Pressure on the Strain Deformation of Flexible Wing Skin Film
## 4 Results and Discussion
### Analysis of the Strain Deformation of Flexible Wing Film
So, this shows that excessive internal inflation pressure could directly lead to a rapid increase in the strain deformation of the lower surfaces of the flexible wing. And the strain deformation of the lower surfaces is positively correlated with the internal inflation pressure. Then, the increase in the internal inflation pressure also helps to improve the overall bearing stiffness of the flexible wing. However, the strain deformation is also increased synchronously, so the direct influence of the deformation of the lower surfaces of the skin film needs to be considered when increasing the internal inflation pressure load. However, properly increasing the inflation pressure inside the flexible wing is also quite beneficial to more uniform strain deformation of the wing tip of the lower surfaces of the flexible wing, which helps to alleviate the local wrinkling problem generation of the lower wing tip of the flexible skin film caused by the smaller aerodynamic load. It can be seen from the main strain deformation cloud that the maximum principal strains of the upper and lower surfaces of the flexible wing are all located near the wing root, the strain deformation near the wing root is significantly higher than that of other areas of the flexible inflatable wing, and the strain deformation of the lower surfaces is higher than the strain value at the same position of the upper wing surfaces. The strain deformation of the leading edge and the trailing edge of the upper and lower surfaces is relatively small; this is mainly because the curvature radius of the skin film deformation at this position is quite small, which could verify the theoretical analysis of Formulas (5)-(8), while the minimum principal strain range is only 1.380 \(\times\) 10\({}^{-5}\)-1.564 \(\times\) 10\({}^{-5}\), which indicates that the minimum principal strain is quite small. And the maximum principal strain range reaches 1.157 \(\times\) 10\({}^{-2}\)-1.336 \(\times\) 10\({}^{-2}\), which shows that the range of strain deformation varies greatly for the flexible inflatable wing film under different inflation pressure conditions. Therefore, the relationship between the local maximum strain deformation and the inflation pressure needs to be considered together when the flexible wing is inflated, and the inflation pressure should not exceed the allowable strain deformation range that the flexible skin film could withstand. Analysis of Strain Deformation Along the Different Characteristic Line Positions of the Flexible Wing Film  
In order to accurately study the strain deformation law of different positions of flexible inflatable wing skin film under the influence of different inflation pressures (1500 Pa, 2000 Pa, 2500 Pa), based on finite element simulation results, the characteristic lines of the upper and lower surfaces of the flexible wing were, respectively, selected as an example. As shown in Figure 6, the spanning characteristic line is in the middle position of the upper and lower surfaces, and the chord characteristic line is in the middle position of the upper surface [6]. Then, the unit nodes on the characteristic line were, respectively, selected, and the spanning direction nodes was selected by a node due to the larger number of adjacent nodes, and the chord-point nodes are continuously selected, and all the node numbers are equally spaced.