Optimization Of Fiber Placement And Strength Analysis Of Composite S Shaped Inlet

The inlet is one of the main components of the modern supersonic fighter, and its aerodynamic performance and structural strength is the key to ensure the normal flight. Many scholars have found that the S shaped inlet has perfect aerodynamic performance. In recent years, carbon fiber composite material has been widely used in the aerospace field because of its light and high strength characteristics. Meanwhile, the fighter can achieve the purpose of stealth with the composite S shaped inlet. In this paper, the fiber placement optimization and strength analysis of composite S inlet are studied by using thin shell equilibrium equation,classical laminated plate theory and Tsai-Wu strength criterion. The main research contents are divided into the following three aspects:(1) According to the central line equation and the area distribution equation, the S shaped inlet is designed,which area of the inlet changes fast at the front part and slowly in the rear part.In addition, based on the basic equations of fluid mechanics and the k-s turbulence model, the flow field characteristics of compressible fluid in the inlet are analyzed. On this basis, when the Maher number is 1.2, the Maher number distribution and the static pressure distribution in the inlet are discussed while the angle of attack at 10 degrees and no angle of attack. The results show that the S shaped inlet has a significant deceleration and boost effect on the fluid, and the influence of the angle of attack on the flow field is not obvious.(2) Based on the equilibrium equation of thin shell, the classical laminated plate theory and the Tsai-Wu strength criterion, the thickness and angle of the initial layer of S shaped inlet are analyzed. Besides, based on the principle of layer planning,the [±?2/(±?2/±?)3/±?]s layer was designed. The results show that the stiffness and strength of the [±?/(±?1/±?)3/±?]s layer are better than that of the [±?12]s layer when the ?=80° and ?=85°. The weight of the layer is reduced by reducing the number of layers and local thickening, and then stiffness and strength of the layer is optimized by changing the ply angle. The results show that the stiffness andstrength of the [36+18] layer [5/-80/(±80/±85)/(±802/±85)2]s+[±809] meet the performance requirements, and its weight is reduced by 20.81% compared with the 48 layer, namely 24.9701kg.(3) The basic idea of variable angle fiber placement and principal stress method are introduced, and the material properties of the unit are calculated by the distance weighting method. The 5° layer and the principal stress layer are used to thicken the two sides of the inlet of the [34+22] layers [-80/±80/±85/(±8O2/±85)2]s+[±8011] to optimize the strength. The results show that the two methods have greatly reduced the Tsai-Wu strength index, and the thicker the layer, the more obvious the principal stress method. Compared to the 48 layer, the weight of the [34+22] layer [-80/±80/±85/(±802/±85)2]s+[±8011] with thicken the two sides of the inlet is reduced by 23.69%, namely 28.4255kg.