Preprint of "Effects of DLP 3D Printing Conditions on Strength and Fracture Toughness of Al2O3/ZrO2 Ceramics"

Vat photopolymerisation via digital light processing enables fabrication of complex ceramic components, but mechanical reliability is limited by defects and anisotropy. This study evaluates the effects of curing energy, printing orientation, and multimaterial processing on flexural strength and fracture toughness of alumina and Al₂O₃/ZrO₂ laminates. An optimal curing energy of 200 mJ/cm² maximised green strength (15 MPa) while minimising lateral overpolymerisation. Sintered alumina showed orientation-dependent behaviour, with Weibull strengths of 359 MPa (horizontal) and 345 MPa (vertical) and Weibull moduli of 7.6 and 23.3, indicating differing flaw populations and scatter. Fracture toughness peaked for cracks propagating perpendicular to layers (K_Ic ≈ 4.9 MPa·m^0.5). Fractography revealed failure dominated by surface and interlayer defects, including pores and cracks, with a bimodal flaw distribution. Multimaterial Al₂O₃/ZrO₂ laminates exceeded 700 MPa strength due to zirconia reinforcement and residual stresses, though cross-contamination and layer defects remain key limitations to reliability.