Highly strengthening and toughening biomimetic ceramic structures fabricated via a novel coaxially printing

Additive manufacturing technology, by manipulating and emulating inherent multiscale, multi-material, and
multifunctional structures found in nature, has created new opportunities for constructing heterogeneous structures
associated with special properties and achieving ultra-high mechanical performance and reliability in ceramic composite materials. In this study, we have developed an innovative fabrication method designated as coaxial 3D printing for the synchronous construction of two constituents into ceramic composites with a tooth enamel biomimetic microstructure. Herein, the stiff silicate and flexible epoxy served as a strengthening bridge and toughening layer, respectively. The method differed from the traditional approach of randomly dispersing reinforcing components within a ceramic matrix. It allowed for the direct creation of an internally effective three-dimensional reinforcement network structure in ceramic composites. This process facilitated synergistic deformation and simultaneous enhancement of multiple materials and hierarchical structures. Owing to the uniform distribution of internal stress and effective block of microcrack propagation, the biomimetically structured silicate/epoxy ceramic composite has demonstrated much significant enhancement in mechanical properties, including compressive strength (48.8±3.12 MPa), flexural strength (10.39±1.23 MPa), and flexural toughness (218.7±54.6 kJ/m3), which was 0.5, 2.1, and 47.5 times as high as those of the intrinsic brittle silicate ceramics, respectively. In-situ characterization and multiscale finite element simulation of microstructural evolution during three-point bending deformation further validated multiple-step features of the fracture process (silicate bridge fracture, interface detachment, epoxy extraction, and rupture), which benefited from interpenetrating structural features achieved by coaxial printing to accomplish with the complex propagating routines of the crack deflection in silicate ceramic composites. This coaxial 3D printing method paves the way for tailored toughening−strengthening designs for other brittle engineering ceramic materials.