Bioinspired design of triboceramics: Learning from the anisotropic micro-fracture response of dental enamel under sliding contact

[EN] In the quest for novel ceramics for tribological applications via bioinspired design, the differences in the fracture modes that arise upon scratching relevant locations of ceramic-like tooth enamel are investigated. It is found that fracture initiates from weak rod-sheath interfaces at relatively low loads, independent of the sliding direction. However, the geometry and propagation of the cracks depends on the orientation of the interfaces relative to the maximum tensile stress: scratching along the occlusal surface propagates approximately sinusoidal cracks, parallel to the sliding direction, while scratching along the cross-section produces straight cracks that propagate normal (scratch parallel to occlusal surface) or parallel (scratch perpendicular to occlusal surface) to the sliding direction. The formation of cracks is hindered in scratching near the enamel-dentine junction. Implications for the microstructural design of triboceramics (bulks and coatings) with improved durability are discussed.