# 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  
Different internal inflation pressure loads have a direct influence on the deformation of the flexible inflatable wing skin film, which determines the deformation and overall bearing stiffness characteristics of the inflated wing skin film. The stiffness deformation characteristics would further affect the mechanical properties of the flexible wing subjected to flight aerodynamic loads and the carried functions, which in turn affects the flight performance. In order to compare the strain deformation characteristics of the skin film of the inflatable wing under different inflation pressure loads, combined with the finite element simulation calculation method, differential inflation pressure loads (1500 Pa, 2000 Pa, 2500 Pa) were selected for the comparison calculation. And the strain deformation of the flexible skin film under the influence of different inflation pressure loads (that is, the internal and external inflation pressure difference and the external environmental pressure remains unchanged) calculated by finite element simulation are shown in Figures 4 and 5. Figure 4: The strain deformation cloud image of the flexible inflatable wing upper surface. With the increase in the inflation pressure, the gradient of the strain deformation change in the upper surfaces gradually decreases, and the strain deformation of the upper wing skin tends to change over a wide range. The front edge and the trailing edge of the wing surface are strain-deformed. However, as the inflation pressure increases, the  
Figure 5: A strain deformation cloud image of the flexible inflatable wing lower surface. change is not obvious, but the overall deformation is quite large. Therefore, the flexible inflatable wing needs to focus on the flexible deformation characteristics of the wing surface. Furthermore, this indicates that within the allowable range of rigidity and strength of the flexible skin film material, if the inflation pressure inside the flexible wing could be appropriately increased, it would be quite beneficial for more uniform strain deformation of the upper wing skin film of the flexible wing, which would also help to alleviate the twist wrinkle problem excessively caused by the aerodynamic load, and also contribute to the distribution of the pressure load on the flexible inflatable skin film. From Figure 5, with the same flexible wing skin material, the main strain deformation of the lower surfaces of the flexible wing is also basically the same along the spanning direction. The strain of the leading and trailing edge near the wing root has the largest deformation, which gradually decreases along the spanning direction, while the strain deformation in the middle region of the lower wing surface is significantly larger than the leading and trailing edges of the same string length/area. Therefore, this indicates that the lower wing surface of the flexible wing has shear strain deformation along the spanning direction, and the middle part of the lower surfaces is the main area of the strain deformation. Moreover, the strain deformation of the sub-region may affect stiffness deformation and cause the excessive deformation of the flexible wing to become damaged. Furthermore, with the increase in the internal inflation pressure, the strain deformation near the wing root increases, and the strain deformation near the leading edge and the trailing edge of the wing tip decreases to some extent. This is because the curvature of the film itself is relatively large near the wing tip, and the large inflation pressure helps to relieve the strain deformation near the wing tip. However, as the internal inflation pressure increases, the strain deformation of the lower surfaces gradually increases as a whole and increases synchronously along the spanning and the chord direction of the flexible wing.