Abstract: A back-thrust drone fuselage with balsa core and carbon fiber sandwich composite structure is designed. The aerodynamic shape design, flow field analysis and internal structure design of the fuselage are completed. The finite element model of the fuselage structure is established and the structure stiffness is checked. The 3D Hashin failure criterion is embedded in the analysis model by subroutine programming. The ultimate state function g(x) is constructed based on the three failure modes, and the strength and stability of the fuselage structure are checked. The initial damage location and mode of the structure are predicted by overload with constant step. The fuselage skin ply optimization is carried out, and the fuselage structure performance with different skin ply is assessed using g(x) function. It is showed that the maximum aerodynamic pressure of fuselage skin for landing and maximum speed flight occurs at the nose fairing area. The values of the ultimate state function g(x) of the two load cases are greater than 0, and the maximum displacement is 3.076 mm and 2.92 mm respectively. The fuselage structure stiffness, strength and stability are verified. With the loading of 1.17 times of the design load to the landing case, the initial compression delamination damage of the balsa core occurs on the lower panel of the fuel tank compartment. The local buckling is found on the fuselage side skin, and the stability of the skin can be improved with the proportion increase of the 45° ply. The structure stability margin is increased by 7.2% due to glass fiber skin ply optimization without weight change.

Key words: balsa core, carbon fiber, composite, drone, design, strength