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.
Highlights
Compared with the contemporary manufacturing technology of humanity, nature has achieved great successes that can provide us with direct clues in designing lighter, stronger and tougher materials[1,2,3]
Despite some limited studies on the toughening mechanisms of conch Strombus gigas shell, there is still a lack of systematic understanding on the toughening mechanisms in the crossed-lamellar structure in Cymbiola nobilis shell. It is unclear whether the channel cracking and crack bridging occur along the specific lamellae interfaces like conch Strombus gigas shell, and how different toughening mechanisms act synergistically during deformation
It is clearly seen that the crossed-lamellar structure exhibits different morphologies along two nearly vertical directions with respect to the arrangement of the 1st-order lamellae, i.e., one being the tiled direction (Fig. 1(c)), and the other being the stacked direction (Fig. 1(e))
Summary
Compared with the contemporary manufacturing technology of humanity, nature has achieved great successes that can provide us with direct clues in designing lighter, stronger and tougher materials[1,2,3]. Despite some limited studies on the toughening mechanisms of conch Strombus gigas shell, there is still a lack of systematic understanding on the toughening mechanisms in the crossed-lamellar structure in Cymbiola nobilis shell It is unclear whether the channel cracking and crack bridging occur along the specific lamellae interfaces like conch Strombus gigas shell, and how different toughening mechanisms act synergistically during deformation. The purpose of this investigation was, to study the mechanical response of the crossed-lamellar structure in a C. nobilis shell under stepwise compressive deformation, focusing on toughening mechanisms. This study will provide a theoretical basis for developing high-performance biomimetic structural materials
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