New toughening concepts for ceramic composites from rigid natural materials

The role of organic proteins on the crack growth resistance of human enamel

“…In highly mineralized biomaterials such as enamel and nacre the proteins are credited with several energy dissipation mechanisms including viscoelastic deformation, crack divergence, crack branching and delamination [38]. The origin of this superior behavior of proteinized systems occurs at the nano-scale of all natural materials comprised of staggered structures [69].…”

“…Of course, proteins function as a cohesive medium facilitating stress transfer between the minerals constituents [30,31]. As such, they play an important role on the mechanical behavior of natural materials including their capacity for viscoelastic/viscoplastic deformation, creep response and toughness [32–38]. Yet, the specific contribution of the proteins in bestowing toughness to these materials is not clearly understood.…”

Mechanical properties of luffa sponge

“…Furthermore, over millions of years to accommodate the natural environment to which they were exposed, a large number of biological systems evolve periodic cells with self-similar hierarchical microstructures. Similar to turtle's shell (Damiens et al, 2012), jellyfish mesogloeas (Zhu et al, 2012), wood (Stanzl-Tschegg et al, 2011;Wegst, 2011), and E. aspergillum sponge (Mayer, 2011), those hierarchical architectures are optimised or partially optimised and can achieve multi-functions with high toughness and efficiency. As we approach the limit of non-renewable natural resources, these properties are essential for the long-term sustainability of our habitat, and is becoming increasingly significant to human civilisations (Zhang et al, 2011).…”

On flaw tolerance of nacre: a theoretical study

“…The shielding effect of microvoids on the crack-tip stress field and its contribution to material strength can be estimated by a combination of the fracture mechanics method presented here and a damage mechanics model accounting for distributed microvoids, but is omitted in this work for simplicity. In addition, nonlinear fracture mechanics methods based on such concepts as the J-integral can be used to address the toughening effects of crack diversion, the frictional effects from platelet sliding, the viscoelasticity and plasticity of the organic constituent, and other nonlinear mechanisms [42]. In this work, we use the concept of stress intensity factor (SIF) to investigate the crack-bridging effect of platelets.…”