Cymbiola nobilis shell: Toughening mechanisms in a crossed-lamellar structure

Abstract

Natural structural materials with intricate hierarchical architectures over several length scales exhibit excellent combinations of strength and toughness. Here we report the mechanical response of a crossed-lamellar structure in Cymbiola nobilis shell via stepwise compression tests, focusing on toughening mechanisms. At the lower loads microcracking is developed in the stacked direction, and channel cracking along with uncracked-ligament bridging and aragonite fiber bridging occurs in the tiled direction. At the higher loads the main mechanisms involve cracking deflection in the bridging lamellae in the tiled direction alongside step-like cracking in the stacked direction. A distinctive crack deflection in the form of “convex” paths occurs in alternative lamellae with respect to the channel cracks in the tiled direction. Furthermore, a barb-like interlocking mechanism along with the uneven interfaces in the 1st-order aragonite lamellae is also observed. The unique arrangement of the crossed-lamellar structure provides multiple interfaces which result in a complicated stress field ahead of the crack tip, hence increasing the toughness of shell.

Mechanical properties of Chamelea gallina shells at different latitudes

“…As anticipated above, the complex fracture behaviour of C. gallina shells, emerging from Figure 5, can be attributed to their multiscale architecture, which allow different energy-dissipating mechanisms. As observed also in other seashells (Espinosa et al, 2011;Ji et al, 2017) and nacre-like materials (Kakisawa and Sumitomo, 2011;Huang and Li, 2013;Yuan et al, 2016), on one side one of the core mechanisms is the deformation of the aragonite microplatelets and their sliding, closely related to the shear strength of the interfaces; while on the other side, the crack propagation between the lamellae (and inside the lamellae at higher loads), which drive the crack path towards the regions with larger stress intensities.…”

Failure mechanisms of biological crossed-lamellar microstructures applied to synthetic high-performance fibre-reinforced composites

“…One example of such microstructure found in biological composites is the crossedlamellar microstructure, the most common microarchitecture within molluscs [10]. The crossed-lamellar microstructure varies slightly between different species and it has been experimentally characterised in the literature [10][11][12][13][14][15][16][17][18], with a vast amount of research focusing on the Strombus gigas shell (Figure 1(a)) [19][20][21][22][23][24][25][26][27]. The microstructure of the Strombus gigas shell will therefore be used as an example of such microstructure in this paper.…”

Conchixes: organic scaffolds which resemble the size and shapes of mollusks shells, their isolation and potential multifunctional applications

“…Molluscan shells are the objects of intensive scientific investigations, mostly as model structures for understanding biomineralization principles [2][3][4][5][6], as indicators of environmental changes with respect to climate [7,8], or chemical contaminations [9,10]. Special attention has been given to shells' biomechanical [11][12][13][14][15][16], biomimetic, and materials science properties [17][18][19][20][21][22][23][24].…”