In-situ 4-point flexural testing and synchrotron micro X-ray computed tomography of 3D printed hierarchical-porous ultra-high temperature ceramic

Additive Manufacturing 2022 Volume 54, Article 102728

3D printed ceramics have received much attention of late due to the ability to manufacture complex near net shapes with a range of structures across multiple length scales. The introduction of hierarchical features offers a wider array of properties, yet with this comes additional unknowns as to their limits including the mechanisms behind failures. The present work applies in-situ Synchrotron micro X-ray computed tomography (μXCT) with 4-point flexural testing to study and further understand the failure pattern of 3D printed hierarchical porous ultra-high temperature ceramics. Samples were imaged at incremental load steps to observe the propagation of defects until final failure, where in the case of the strain tolerant logpile structure a full crack spanning the height and width of the sample was captured and reconstructed revealing a complex tortuous fracture path. The relative strength and density of the structures are related to the sintered microstructure and the printed logpile or honeycomb geometry, which are described using Gibson’s and Ashby’s theory for brittle foams. In addition, tomographic data was used to extract detailed information on porosity and material density distribution within honeycomb and logpile 3D printed lattice structures that was related to the tool path planning of each layer.