组合式铝蜂窝异面压缩响应及缓冲吸能特性研究

Aluminum honeycomb is a good energy-absorption material because of its high strength and low density, and is widely used as energy absorbers and protective components in various industries such as automotive, aerospace, car, ship and other engineering sectors. According to the existing literatures, mang studies are carried out which mainly focused on the following aspects: the out-of-plane and in-plane crushing behavior of single aluminum honeycombs; mechanical behavior of aluminum honeycomb sandwich panels. In this work, we focus on the out-of-plane inserting and crushing behavior of combined aluminum honeycomb structures, in which the honeycomb samples are stacked without lining boards and can insert into each other. This can privide a new idea for the energy-absorbing design of aluminum honeycomb. Firstly, the dynamic cushion is investigated using modified split Hopkinson pressure bar. Then cushion energy absorbing property are analysed on the base of the dynamic and quasi-static experimental results. Secondly, the embedding and buckling process of combined honeycombs will be simulated by finite element model, in which a reasonable model and failure criterion will be established. Then the inserting and buckling mechanism can be investigated in detail. Thirdly, theoretical model will be constructed, which can predict the total process of inseting and buckling of the combined aluminum honeycombs. As a result, cushion energy absorbing property of different combined aluminum honeycombs are compared, and a design principle is given.

铝蜂窝具有密度低，比强度高，压缩应变大和能量吸收能力强等特性，是一种较为理想的轻质结构材料，在航空航天、汽车工业、交通运输等领域有广阔的应用前景。前期很多学者已对单一铝蜂窝面内、面外（也称异面）压缩特性、铝蜂窝夹心结构开展了大量的研究，取得了系列成果。本项目选取组合式铝蜂窝（多个蜂窝试样直接叠加的组合体）为研究对象，重点研究其相互嵌入和屈曲特性，以期为铝蜂窝的缓冲吸能设计提供新思路。通过改进SHPB实验技术实现对组合铝蜂窝的大应变动态压缩研究，结合准静态实验获得组合式蜂窝的压缩响应规律；建立合理的有限元模型和失效判据，对组合铝蜂窝的嵌入和屈曲过程进行全过程仿真，结合实验结果分析其嵌入特性和机理；希望开发和建立可以描述组合式铝蜂窝插入过程及屈曲全过程的理论模型。同时，从缓冲吸能角度出发，研究不同形式组合蜂窝的缓冲吸能特性，给出组合铝蜂窝的缓冲吸能设计原则和依据。

组合式蜂窝是多层蜂窝直接叠加、不添加固体隔板的组合体，通过改变蜂窝的类型和截面积等，可以得到形式丰富的组合体，有助于更灵活地设计缓冲吸能结构。但是，组合铝蜂窝的吸能机制与传统蜂窝存在比较明显的差异，关于其相互嵌入的力学机制和理论模型研究还比较欠缺。. 本项目选取组合式铝蜂窝为研究对象，通过试验和仿真研究了其相互嵌入和吸能特性。首先，试验研究了其准静态下的相互嵌入现象和应力响应，结果表明组合式铝蜂窝结构压缩全过程中存在两个应力平台：互嵌入平台和共同压缩平台，且90°堆叠铝蜂窝的平均嵌入应力比0°的组合体要高30%；中低速动态加载实验结果表明，和90°堆叠铝蜂窝相比，0°结构嵌入应力的加载率相关性更强。理论分析方面，在实验结果基础上，建立了表征铝蜂窝特性参数的理论公式；基于量纲分析法和考虑等效嵌入点数目的统计方法，定量描述了组合式铝蜂窝的嵌入平台应力；基于Johnson-Cook材料模型，提出了组合式铝蜂窝动态嵌入平台应力和共同屈曲压溃应力的半经验理论模型。在仿真方面，利用“Y”形结构等效模型实现了对单层蜂窝结构压缩过程和组合式铝蜂窝嵌入过程的模拟；并对组合式蜂窝进行整体建模，对嵌入和压缩过程进行了模拟，得到了蜂窝结构响应机理的细节描述。在缓冲吸能机制方面，分析了组合式蜂窝结构变形过程和缓冲吸能特性，结果表明嵌入阶段所吸收能量约占总吸能的25%，且存在两个相近的吸能效率峰值，均约为40%；和准静态结果相比，动态冲击下组合式蜂窝吸能效果更好，但其嵌入过程占总吸能比更小。最后，设计并开展了组合式铝蜂窝平板降冲击试验，分析了蜂窝结构胞元边长与相对厚度两个主要因素对降冲击性能影响，确定了比较理想的降冲击组合式铝蜂窝试样选型方法。. 本项目的研究成果，有助于从物理机制上理解组合式蜂窝的缓冲吸能过程，对于指导组合式蜂窝在更多领域的降冲击应用具有比较直接的借鉴意义。