Failure mechanisms of lightweight high strength Si/SiC non-uniform lattice structures by SLS/RMI

Abstract

Silicon Carbide (SiC) ceramic lattice structures were pivotal in advancing space technology and other sectors by merging structural lightness with high strength. This study explored non-uniform lattice designs tailored for specific load-bearing applications to maximize lightness, although machining such SiC structures proved challenging due to their high hardness and wear resistance. Selective Laser Sintering (SLS) was employed to fabricate non-uniform lattice structures featuring graded volume fractions. Micro computed tomography (Miro-CT) characterized the geometric characteristics of the macroscopic non-uniform lattice structure. Extensive investigations were conducted on the impact of these gradient structures on the quasi-static compressive behavior and mechanical properties of SiC ceramics, revealing that the R-A structure achieved a maximum compressive strength of 14.989 MPa and a specific strength of 13.268 × 10³ N·m/kg, approximately double that of a uniform structure. Furthermore, a finite element model (FEM) was established to verify and predict the mechanical and fracture responses of SiC-based structures, showing effective dispersion of stress concentration along the outer rim of the R-A structure, markedly alleviating the usual stress concentration found in traditional lattices and averting catastrophic failure. The alignment between experimental and simulation outcomes substantiated these findings.