小型化单胞Al基点阵材料设计、制备与力学行为

Lattice materials are truss like ordered porous materials composed of nodes and connecting struts, in which light alloy based materials show not only outstanding specific strength, rigidity and energy absorption capacity but also excellent sound absorption, damping, heat transfer and electromagnetic shielding properties. However, the current technologies can be only capable of manufacturing lattice materials with quite simple, less-layer and relatively large unit cells, and thus we have little knowledge of the mechanical properties and their dependences on the structures of metallic lattice materials with small cells and complicated topologies, as well as failure modes and optimization methods up to date. Therefore, the present proposal is going to conduct investigations into the design and preparation of aluminum alloy based lattice materials with small unit cells, multi-structures and multi-layers by utilizing computer aided design and 3-D printing techniques in combination with our patented technologies for fabricating small cell aluminum foams. Subsequently, the mechanical behaviors of resultant materials are studied both numerically and experimentally. The effects of unit cell dimensions, structures and layer numbers on the overall mechanical properties and related mechanisms are to be disclosed through examining the deformation, failure and destroy features of the materials. The relationship between the mechanical properties and lattice structures will be established to give guidelines for the structure design and property optimization. Moreover, the manufacturing technologies for the small unit cell lattice materials are expected to provide a critical base for the design and realization of functionalities of metallic lattice materials, such as sound absorption, damping, heat transfer and electromagnetic shielding, etc.

点阵材料是一种由节点和连接杆元组成的空间网架类有序多孔材料，其中基于轻金属的点阵材料具有突出的比强度、比刚度、比吸能性以及吸声、阻尼、换热和电磁屏蔽等功能。本项目针对目前金属点阵材料构型单一、层级较少、单胞尺度偏大的问题，以及有关复杂构型、小型单胞及多层结构力学行为及其与点阵结构的关系认识不足的现状，拟首先开展铝基点阵材料设计和制备方法的研究。利用计算机辅助设计和3D打印技术，结合本单位在网络状微孔泡沫铝方面的研究基础，制备出小单胞、多构型、多层级的铝基点阵材料，然后对其力学行为进行数值模拟和实验研究，对单胞及整体点阵材料形变、损伤及破坏方式进行观察，以揭示其尺度、构型及层级等对点阵材料整体力学行为的影响及其机制，阐明单胞、点阵结构与力学性能的关系，为金属点阵材料设计与性能优化提供依据。有关小尺度单胞的制备方法还有望为点阵材料吸声、阻尼、换热和电磁屏蔽等功能设计奠定重要基础。

围绕项目拟定的研究内容和目标，对小尺寸（结构参数为毫米量级）、多构型Al基点阵结构设计、制备、表征及性能等进行了研究，为结构性、功能性点阵结构设计和性能优化提供了依据。.采用CATIA三维画图软件设计出了金字塔型、Kagome型、四面体型、拉胀型以及基于点阵结构的复合结构等。结合3D打印技术和熔模渗流方法，制备出了杆径2.0mm、杆长10.0mm的多种小尺度Al 基点阵结构。.研究表明，Al基点阵结构压缩行为与一般多孔金属材料相似，压缩应力应变曲线也具有明显的线弹性区、平台区和致密化区。基体材料一定时，各区域特征以及点阵结构整体强度与结构参数密切相关，但均可归纳为与点阵结构相对密度的关系。引起点阵结构相对密度增加的参数变化，均使点阵结构强度增加。.Al基点阵结构的压缩变形模式取决于杆元/投影面的夹角。夹角小于45时，变形模式为整体同时发生弯折，变形组织分布均匀；夹角大于45时，则表现出明显的局域化特征，变形从中间层杆元开始，逐渐向上下两端扩展，直至失稳和致密化。杆元截面形状对点阵结构变形方式及抗压强度也有很大影响。相对密度相同、夹角较大时，U形截面杆元点阵结构抗压强度是圆形截面的2倍以上。夹角相同、相对密度接近时，四面体型Al基点阵结构强度和吸能性均明显高于金字塔型。.与传统点阵结构和多孔材料相比，Al基拉胀结构具有更高的弹性模量和抗压强度。在Al基拉胀结构中填充粘弹性材料，因金属杆元变形受阻，变形难度增大，故使点阵结构抗压强度提高，同时向拉伸主导型变形转变。将复合拉胀结构填入金属管内，形成内外约束条件，可显著提高组合结构的抗压强度和力学效率。