Assessment of mechanical performance of Al2O3 ceramic honeycomb sandwich structures produced with SLA 3D-printing regarding unpolymerized slurry removal strategy

Al₂O₃ ceramic honeycomb sandwich bars with a hexagonal core were manufactured through SLA 3D-printing to analyze the impact of hole placement, designed for the removal of uncured slurry, on the bending strength of the samples. Several holes were placed specifically on the samples in the design in two different ways. In the initial design, the holes were placed on the honeycomb sandwich structure’s upper and lower face-sheets. In the second design, the holes were positioned in the direction of the sample thickness, in the lateral walls. The moment of inertia values for the honeycomb structures were calculated with the help of experimental elastic modulus results, and true bending strength was determined according to these results. Nominal strength values were found using the common three-point bending formula. The true bending strength value of Al₂O₃ with lateral holes was 73% higher than Al₂O₃ with holes on face-sheets, while the nominal bending strength was 79% higher. Al₂O₃ samples with holes on face-sheets exhibited a significantly higher failure index compared with both the bulk samples and the Al₂O₃ samples with lateral holes. The holes on the face-sheets reduced the cross-sectional area of the tensile surface and contributed to an increase in stresses due to the stress concentration effect. The Al₂O₃ samples with lateral holes provided a great advantage of specific strength, reaching an average value of 65% above the specific strength of the bulk samples.