Tian Yuanyuan, Zhang Xin, Hou Boyuan, Jarlöv Asker, Du Chunyang, Zhou Kun
HP-NTU Digital Manufacturing Corporate Lab, Nanyang Technological University, Singapore 639798, Singapore.
Singapore Centre for 3D Printing, School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore.
Proc Natl Acad Sci U S A. 2024 Oct 22;121(43):e2407362121. doi: 10.1073/pnas.2407362121. Epub 2024 Oct 14.
Shear bands frequently appear in lattice architectures subjected to compression, leading to an unstable stress-strain curve and global deformation. This deformation mechanism reduces their energy absorption and loading-bearing capacity and causes the architectures to prioritize mechanical protection of external components at the expense of the entire structure. Here, we leverage the design freedom offered by additive manufacturing and the geometrical relation of dual-phase nanolamellar crystals to fabricate heterogeneous lamellar lattice architectures consisting of body-centered cubic (BCC) and face-centered cubic (FCC) unit cells in alternating lamella. The lamellar lattice demonstrates more than 10 and 9 times higher specific energy absorption and energy absorption efficiency, respectively, compared to the BCC lattice. The drastic improvement arises as the nucleation of shear bands is inhibited by the discrete energy threshold for plastic buckling of adjacent heterogeneous lattice lamella during loading. Despite its lower density than the FCC lattice, the lamellar lattice exhibits significant enhancement in plateau stress and crushing force efficiency, attributed to the strengthening effect induced by simultaneous deformation of unit cells in the BCC lattice lamella and the resulting cushion shielding effect. The design improves the global mechanical properties, making lamellar lattices compare favorably against numerous materials proposed for mechanical protection. Additionally, it provides opportunities to program the local mechanical response, achieving programmable internal protection alongside overall external protection. This work provides a different route to design lattice architecture by combining internal and external dual mechanical protection, enabling a generation of multiple mechanical protectors in aerospace, automotive, and transportation fields.
在承受压缩的晶格结构中，剪切带经常出现，导致应力-应变曲线不稳定和整体变形。这种变形机制降低了它们的能量吸收和承载能力，并使结构优先考虑对外部部件的机械保护，而以整个结构为代价。在此，我们利用增材制造提供的设计自由度以及双相纳米层状晶体的几何关系，制造出由体心立方（BCC）和面心立方（FCC）晶胞交替排列组成的异质层状晶格结构。与BCC晶格相比，层状晶格的比能量吸收和能量吸收效率分别高出10倍和9倍以上。这种显著的改善是由于在加载过程中，相邻异质晶格层片塑性屈曲的离散能量阈值抑制了剪切带的形核。尽管层状晶格的密度低于FCC晶格，但由于BCC晶格层片中晶胞同时变形所产生的强化效应以及由此产生的缓冲屏蔽效应，层状晶格在平台应力和破碎力效率方面有显著提高。该设计改善了整体力学性能，使层状晶格优于许多用于机械保护的材料。此外，它还提供了对局部力学响应进行编程的机会，在实现整体外部保护的同时实现可编程的内部保护。这项工作通过结合内部和外部双重机械保护提供了一种设计晶格结构的不同途径，有望在航空航天、汽车和交通运输领域催生多种机械保护装置。
