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The oxidation‐induced crack healing of an Al2O3 composite loaded with various volume fractions of Ti2Al0.5Sn0.5C repair filler particles was investigated by annealing in air at a relatively low temperature of 700°C. After annealing a composite with 20 vol.% repair fillers (with a particle size of ~5.6 µm) for 48 hours, artificial indentation cracks prepared on the surface, as well as pores near the surface, were completely healed by filling with condensed oxidation products. Additionally, minor fraction of metallic Sn was detected. A complementary study by X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy dispersive X‐ray spectroscopy revealed that nano‐sized oxidation products (SnO2, TiO2, and α‐Al2O3 phase) were formed as major crack‐filling species. After healing, the strength recovery of the Al2O3 composites was significantly improved in the composites loaded with more than 10 vol.% repair fillers and achieved 107% at 700 for 48 hours.

Modular composites with a 3D periodic structure, consisting of a major brittle inorganic phase (building blocks) and a minor viscoelastic organic matrix, offer great potentials for improved fracture toughness and failure probability in polymer‐ceramic composites. Alumina building blocks with dimensions of 1500 μm were assembled by a novel placing system equipped with an automatic optical inspection (AOI) system. The AOI system coupled with shape recognition enables simultaneous dimensional characterization, tolerance sorting, and flexible placing of different shaped building blocks. 3D periodic structures with cubic, monoclinic, and triclinic unit cells were fabricated by high accuracy placing of cubic building blocks enabling near‐net shape manufacturing. The placing precision of the assembled structures was determined by μCT to have a maximum deviation of ±78 μm. The structures were afterward infiltrated with a soft epoxy resin to fabricate epoxy‐alumina composites. The brick‐and‐mortar like building block arrangements of the monoclinic and triclinic structures exhibited improved bending strength, fracture toughness, and failure probability compared to monolithic epoxy, due to crack deflection and pull‐out toughening mechanisms. A maximum bending strength of 35.1 ± 7.5 MPa, a work‐of‐fracture of 814.7 ± 255.1 J/m² and a calculated fracture toughness of 4.8 ± 0.8 MPam for the triclinic structures was achieved.