机载红外成像系统主支撑结构新型轻量化设计方法与应用

由于载机负载有限，质量一直是机载成像系统结构设计时的关键指标。主支撑结构作为机载成像系统中光学系统的主承力结构，必须进行轻量化设计。但是，以往机载成像系统主支撑结构轻量化设计方法主要包括选择比刚度高的金属材料、优化框架结构布局、调整壁厚、增加减重槽等具体措施。由于金属材料的密度和线膨胀系数较高，这种轻量化设计方法的轻量化程度不高，且有时无法满足高精度光学系统无热化设计的要求。因此，提出了一种复合材料与金属材料相结合的新型轻量化设计方法，利用更低密度、更低线膨胀系数的碳纤维复合材料作为主支撑结构成型材料，钛合金作为对外接口材料，并以质量最轻为目标、基频为约束进行了参数优化设计，最后采用预浸料制造与铺放方法获得了更高轻量化、更优尺寸稳定性的主支撑结构。通过数值计算、仿真分析与振动试验对新方法的有效性进行了验证，结果表明:新型轻量化主支撑系统基频为425 Hz；质量为10.5 kg，轻量化率为33.5%；60 ℃均匀温升时轴向光学间隔变化量为0.021 mm，降低了84.9%。研究结果表明:新型轻量化设计方法合理、有效，解决了结构轻量化与光学无热化设计的难题，并应用到长焦距大口径机载红外成像系统中。

New lightweight design method and application of main support structure in airborne infrared imaging system

Due to the limited load of aircraft, weight was always the key index in the structural design of airborne imaging system. As the main load bearing structure of the optical system in the airborne imaging system, the main support structure must be lightweight. However, the previous lightweight design methods for the main support structure of airborne imaging system mainly included specific measures such as selecting metal materials with high specific stiffness, optimizing the layout of the frame structure, adjusting the wall thickness, and adding weight loss trough. Due to the high density and linear expansion coefficient of metal materials, the lightness extent of this lightweight design method was not high, and sometimes couldn’t meet the requirements of athermalization design of high-precision optical systems. Therefore, a new lightweight design method combining composite materials and metal materials was proposed. Carbon fiber composite materials with lower density and lower linear expansion coefficient was used as the main support molding material, and titanium alloy was used as the external interface material. The parameter optimization design was carried out with the lightest target as the goal and the fundamental frequency as the constraint. Finally, the main support structure with higher lightweight and better dimensional stability was obtained by using the prepreg manufacturing and laying method. The effectiveness of the new method was verified by numerical calculation, simulation analysis and vibration test. The results showed that the fundamental frequency of the new lightweight main support system was 425 Hz. The weight was 10.5 kg, which was reduced by 33.5%. The variation of axial optical spacing was 0.021 mm at 60 ℃ uniform temperature rise, which was reduced by 84.9%. The research results showed that the new lightweight design method was reasonable and effective, which solved the problem of structural lightweight and optical athermalized design. It was applied to the main support structure of the airborne infrared imaging system.