Speaker
Description
Bio-inspired material are designed by mimicking natural features. Indeed, billion years
of evolution under pressure from their environment have tuned natural structures into
outstanding components. Exemples of such appropriation are common in our everyday
life, from swimming suits inspired by shark skin to Velcro inspired by a particular sort
of seed.
Bio-inspiration can also benefit to structural ceramics. Indeed, their iono-covalent
bondings provide them high strength and high stiffness. However, they generaly exhibit
brittle fracture at ambient temperature. This structural drawback can be limited by
tuning the material architecture. Nacre-like alumina is inspired by natural nacre found
in some moluscs’ shell. Due to its brick-and-mortar architecture, natural nacre exhibit
a toughness ten time higher than that of its constitutive components due to an extrinsic
toughening mechanism of crack deflection.
First nacre like aluminas were produced less than 10 years ago and mechanical characterization confirmed the combination of high toughness and relatively high
strength observed on their natural couterparts. However, this characterization
remained partial, and it demonstrated limitation to adequatly capture the fracture behavior of the material.
Consequently a macroscopic characterization of the fracture phenomenon in the three
main anisotropy directions is performed by combining experiments and simulations. In
that scope, the results of digital image correlation applied to wedge and four-points
bending tests in different directions where used in numerical finite element simulations.
Then, the application of the coupled criterion - a method based on the simultaneous
fulfillment of an energy criterion and a stress criterion - allowed an inverse identification
of the fracture properties at crack initiation. Thus, relationships between the macroscopic properties of the composite, the individual properties of its components and the
microstructure could be determined.
| Speaker Country | France |
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