Intrinsic mechanics of 3D-printed porous polymer-derived ceramic metamaterials

Abstract

Mechanical characterization of additively-manufactured polymer-derived ceramics (PDCs) remains challenging due to pyrolysis-induced porosity, flaws, and internal voids that bias conventional property measurements and mask the intrinsic bulk stiffness required for predictive metamaterial design. In this study, we introduce a hybrid experimental–numerical strategy to extract the intrinsic bulk Young's modulus of porous 3D-printed PDCs independent of their internal void structure. Hollow cylindrical specimens with systematically varied wall thicknesses are fabricated using liquid crystal display (LCD) printing and converted to silicon oxycarbide (SiOC)-based ceramics through pyrolysis. Micro–computed tomography (micro-CT) is used to capture the actual pore architecture, and a pixel-based reconstruction pipeline converts segmented micro-CT data into cubic-element finite element (FE) meshes. Compression tests provide experimental structural stiffness, while compression simulations of the same reconstructed geometries are performed using an assumed bulk Young's modulus. By leveraging geometrically identical models in experiments and simulations, the intrinsic bulk Young's modulus of 3D-printed PDCs is obtained from the stiffness ratio as 1.9 ± 0.1 GPa across specimens with different porosities. To determine the normalized modulus of the porous material, homogenization analyses are conducted on porous representative volume elements, establishing a strong relationship between normalized modulus and porosity. Finally, strut-based ceramic lattice structures are fabricated and tested, and two predictive FE approaches are demonstrated: a detailed FE approach based on micro-CT-reconstructed lattices and a computationally efficient FE–homogenization method using solid lattice geometries with porosity-informed effective properties. The developed hybrid experimental–numerical framework enables a robust extraction of bulk mechanical properties for porous ceramics and supports efficient, scan-light evaluation of the performance of porous ceramic metamaterials.