Research On Structure Optimization And Mechanical Properties Of X-shaped Composite Truss Assembled In Fuel Tank Of Rocket

The new type launch vehicles ask for the demand of high loading capacity and light weight for the main bearing structure.The design and manufacture of the light weight composite truss that meet the loading requirement can implement the reduction of the rocket weight.And it can expand the application of the carbon fiber reinforced composite in main bearing structure.In this paper,X-shaped composite truss,one of the members of the connection adapter assembled in fuel tank of rocket,was being studied.The structure of the X-shaped composite truss was optimized and manufactured.Finally,the mechanical properties were tested to verify the designed results.A optimization flow for composite truss with heavy load,multiple loading condtions and complex spatial structure was established.The main contents are as follow:(1)The cross section was designed to unify the main body of X-shaped composite truss and joint.The X-shaped composite truss was divided into four sections: joint,straight section,transition section and intersection.The configuration of each section was designed.A parametric geometrical model was created in Catia R21.(2)The integral model of the X-shaped composite truss and fuel tanks was developed.Then the deformation of the integral model was analyzed by finite element method.Through the deformation analysis,the displacement boundary condition of the upper joint was determined to be 10 mm outward along the normal direction of joint.(3)7 design parameters selected from 10 parameters of the X-shaped composite truss by sensitivity analysis were used as the optimization parameters in the next stage.The optimization model was developed based on the constraints of strain,the buckling load and the composite Hashin failure factors.The objective of the optimization was to minimize the mass of the X-shaped composite truss.The optimal design was obtained after 1000 iterations through MIGA.The mass of the optimal design(half of the X-shaped truss)is 5.67 Kg,which can deliver up to 10.90% mass savings in comparison with initial design.(4)The check model included detail layup information was developed to obtain the more accurate results.The X-shaped composite truss was manufactured by autoclave process.The maximum strain of key parts of the X-shaped composite truss is 3750 μεwith no obvious phenomenon of destruction,which means the X-shaped composite truss meet the design requirements.