Background

Geometric parameter optimization, novel design, and mechanism modeling of auxetic materials have been widely studied. However, manipulating the topology of the 3d printed auxetic unit cells and its influence on the damage have yet to be explored.

Objective

This study aims to characterize the energy absorption properties and damage mechanisms of the modified auxetic unit cells.

Methods

In the current study, bending-dominated re-entrant auxetic unit cells (Cell0), torsion-dominated auxetic unit cells with cross elements (CellX), buckling-dominated auxetic unit cells with vertical elements (CellB), and bending-dominated auxetic unit cells with panels (CellW) have been fabricated by FDM (Fused deposition modeling). Uniaxial compression testing of the PLA (Polylactic acid) unit cells has been carried out, and a camera has observed their deformation behavior. SR- µCT (Synchrotron radiation microtomography) and an SEM (Secondary electron microscope) accomplished further damage analysis of the struts.

Results

Adding additional struts hinders the lateral shrinking of the re-entrant auxetics, and re-entrant auxetic unit cells with cross elements have shown higher energy absorption capacity and efficiency than others. The struts’ damage has been governed by building direction, printed material, and strut dimensions. Intra-layer and interlayer fracture of the layers and rupture in the circumferential direction of the PLA struts have been observed in the SR- µCT slices.

Conclusions

By additional struts, it is possible to fabricate complex auxetic structures with enhanced energy absorption properties, but their inherent characteristics dominate the damage of the struts in the auxetic unit cells.

Graphical Abstract

中文翻译：

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3D 凹入拉胀晶胞中附加支柱元件对损伤和能量吸收性能的影响

背景

拉胀材料的几何参数优化、新颖设计和机理建模已得到广泛研究。然而，操纵 3D 打印拉胀单元的拓扑结构及其对损伤的影响仍有待探索。

客观的

本研究旨在表征改良拉胀单元的能量吸收特性和损伤机制。

方法

在当前的研究中，弯曲主导的凹入拉胀单元（Cell0）、具有交叉单元的扭转主导的拉胀单元（CellX）、具有垂直单元的屈曲主导的拉胀单元（CellB）和弯曲主导的拉胀单元带面板的电池 (CellW) 是通过 FDM（熔融沉积建模）制造的。对PLA（聚乳酸）晶胞进行了单轴压缩测试，并用摄像头观察了它们的变形行为。 SR-μCT（同步辐射显微断层扫描）和 SEM（二次电子显微镜）完成了支柱的进一步损伤分析。

结果

添加额外的支柱阻碍了可重入拉胀装置的横向收缩，并且具有交叉元件的可重入拉胀单元电池表现出比其他单元更高的能量吸收能力和效率。支柱的损坏取决于建筑方向、印刷材料和支柱尺寸。在 SR-μCT 切片中观察到层内和层间断裂以及 PLA 支柱圆周方向的断裂。

结论

通过额外的支柱，可以制造具有增强的能量吸收特性的复杂拉胀结构，但它们的固有特性主导了拉胀单元中支柱的损坏。

图形概要