Nacre has been considered as one of the most important models for the development of hard bioinspired materials. This aragonite-based layered structure has been extensively studied because of its excellent mechanical properties, superior to those of monolithic aragonite. Calcite-based seashells have received less attention, as they display lower hardness and Young’s modulus. However, layered calcitic structures also have a superior fracture toughness value compared with monolithic calcite. In this paper, seashells of six species were studied by correlating the mechanical properties of the calcite- and aragonite-based layers with their mineral building blocks. Morphological studies revealed nacreous and fibrous prismatic microstructures for aragonite-based layers, whereas calcite-based layers have prismatic and foliated microstructures. The hardness and stiffness of the aragonitic structures were slightly higher than those of calcite. A toughening factor was calculated comparing the fracture toughness of the aragonitic and calcitic layers with the toughness of monolithic aragonite and calcite. The toughening factors of calcitic and aragonitic structures were in the same range (1.6–9.2).

中文翻译：

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通过纳米压痕测试的方解石和文石基结构的机械性能

Nacre被认为是开发硬生物启发材料的最重要模型之一。这种基于文石的层状结构由于其优异的机械性能优于整体式文石而被广泛研究。方解石基贝壳的硬度和杨氏模量较低，因此受到的关注较少。然而，与整体方解石相比，层状钙质结构也具有优异的断裂韧性值。在本文中，通过将方解石和文石基层的力学性能与其矿物构造块相关联，研究了六种贝壳。形态学研究表明，文石基层具有珠状和纤维状的棱柱形微观结构，而方解石基层具有棱柱形和叶状的显微结构。文石结构的硬度和刚度略高于方解石。计算了韧化因子，将文石层和钙质层的断裂韧性与整体文石和方解石的韧性进行了比较。钙质和芳纶结构的增韧因子在同一范围内（1.6-9.2）。