微型蜂窝弹性体超材料尺寸效应的实验全场分析
Experimental Full-field Analysis of Size Effects in Miniaturized Cellular Elastomeric Metamaterials
摘要：
蜂窝弹性体超材料对于各种应用（例如软机器人）是令人感兴趣的，因为它们可以表现出多种微观结构图案变换，每种都具有其特征性的机械行为。数值文献研究表明，斑图形成受到（厚）边界层的限制，导致显著的机械尺寸效应。本文旨在通过实验验证这些研究结果的小型化标本，相关的实际应用，并调查增加的几何和材料缺陷造成的标本小型化的影响。为此，小型化的细胞超材料标本制造不同的比例，进行原位微压缩测试结合数字图像相关产生全场运动学，并比较互补的数值模拟。在屈曲前刚度、屈曲应变和屈曲后应力方面，试件的整体行为与数值预测吻合良好。它们的局部行为，即模式转换和边界层形成，也是一致的实验和模拟之间。这些结果与理想化的数值研究文献的比较揭示了在实际的蜂窝超材料应用中的边界条件的影响，例如横向约束，在尺寸效应和边界层形成方面的机械响应。
英文摘要：
Cellular elastomeric metamaterials are interesting for various applications, e.g. soft robotics, as they may exhibit multiple microstructural pattern transformations, each with its characteristic mechanical behavior. Numerical literature studies revealed that pattern formation is restricted in (thick) boundary layers causing significant mechanical size effects. This paper aims to experimentally validate these findings on miniaturized specimens, relevant for real applications, and to investigate the effect of increased geometrical and material imperfections resulting from specimen miniaturization. To this end, miniaturized cellular metamaterial specimens are manufactured with different scale ratios, subjected to in-situ micro-compression tests combined with digital image correlation yielding full-field kinematics, and compared to complementary numerical simulations. The specimens' global behavior agrees well with the numerical predictions, in terms of pre-buckling stiffness, buckling strain and post-buckling stress. Their local behavior, i.e. pattern transformation and boundary layer formation, is also consistent between experiments and simulations. Comparison of these results with idealized numerical studies from literature reveals the influence of the boundary conditions in real cellular metamaterial applications, e.g. lateral confinement, on the mechanical response in terms of size effects and boundary layer formation.
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