Dynamic mechanical properties of alumina prepared by vat photopolymerization based on high solid loading slurry

The adoption of 3D printing ceramics in military applications such as body armor and ballistic resistant structures has attracted significant research interests. And there is a pressing need to improve the mechanical properties of 3D printing samples compared to their conventionally-prepared counterparts, while understanding their failure mechanisms under quasi-static and impact load. In this study, a 65 vol% Al₂O₃ ceramic slurry with high stability and low viscosity was prepared by optimizing the combination of resin with dispersant, and printed by Vat photopolymerization (VPP) method. This yields sintered specimens with minimal flaws, because of the synergistic effect of the high solid loading and debinding process. Consequently, the compressive and bending strengths of sintered specimens employing this approach are significantly influenced by the solid loading (e.g., the compressive strength of a 28 vol% solid loading specimen is 6 MPa, whereas the compressive strength is 125 MPa for 65 vol% solid loading; similarly, the bending strength is 16 MPa of a 28 vol% solid loading, while that for a 65 vol% solid loading specimen is 75 MPa). Compressive Split Hopkinson Pressure Bar (SHPB) tests show noticeable strain rate sensitivity and anisotropy for 3D printing Al₂O₃. In addition, the mechanisms of the ductile to brittle transition when changing the solid loading and strain rate of the load for 3D printing Al₂O₃ are analyzed.