Tetrahedral and strut-reinforced tetrahedral microlattices: Selectively laser melted high-strength and high-stiffness cellular metamaterials

Abstract

Lightweight materials that possess high strength and stiffness have always been a topic of interest for researchers and industries like defense, automotive and aerospace. A class of such lightweight metamaterial is microlattice, which comprises of architected periodic arrangements of struts or plates. The recent advances in additive manufacturing aid in the fabrication of microlattice at a small length scale with high dimensional accuracy. This work proposes designs of two microlattices, namely tetrahedral and strut-reinforced tetrahedral (SRT), with high specific strength and high specific stiffness. The mechanical behavior of these microlattices was analyzed under quasi-static compressive loading using analytical, numerical and experimental methods and compared with widely studied BCC and BCCZ microlattices having similar architecture. All microlattices were fabricated from AlSi10Mg powder using a laser powder bed fusion technique of additive manufacturing. The strength and stiffness attained by the tetrahedral and the strut-reinforced tetrahedral microlattices were significantly higher than the conventional BCC and BCCZ microlattices of the same relative density, respectively. Two failure modes, i.e., shear failure and crushing, were observed in the microlattices. The orientations of the shear crack planes in the tetrahedral and the BCC microlattices and vertical strut assisted layerwise crushing in the SRT and the BCCZ microlattices were investigated. The focus of the study is to understand the design and mechanical behavior of the tetrahedral and the strut-reinforced tetrahedral microlattices, which can be useful for high-strength and high-stiffness applications.