轻木夹芯/碳纤维复合材料结构后推构型无人机机身设计与分析

Design and analysis of the back-thrust drone fuselage with balsa core and carbon fiber sandwich.composite structure

设计了一款后推构型轻木夹芯/碳纤维复合材料结构无人机机身,完成了机身气动外形设计、流场分析和内部结构设计。建立了机身结构有限元模型,完成了结构刚度校核。编写子程序,将3D Hashin失效准则嵌入计算模型,基于三类失效模式构建极限状态函数g(x),对机身结构进行了强度及稳定性校核。采用等步长施加超设计载荷,预测了结构的初始损伤位置及模式。对机身蒙皮铺层方案进行了优化设计,采用g(x)函数对更改铺层方案后的结构性能进行了评估。研究结果表明:着陆工况和最大飞行速度工况的机身蒙皮表面压强最大值均在机头整流罩区域。两种工况的极限状态函数g(x)均大于0,最大位移分别为3.076 mm和2.92 mm,机身结构满足刚度、强度和稳定性要求。对着陆工况施加1.17倍设计载荷时,油料舱下壁板轻木芯材发生压缩分层初始损伤。机身结构失稳发生于侧面蒙皮,提高45°铺层占比可提高蒙皮的稳定性。玻纤蒙皮铺层优化后,在质量不变的条件下,结构稳定性裕度提高了7.2%。

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.