During billions of years of evolution, creatures in nature have possessed nearly perfect structures and functions for survival. Multiscale structures in biological materials over several length scales play a pivotal role in achieving structural and functional integrity. Fiber, as a common principal structural element in nature, can be easily constructed in different ways, thus resulting in various natural structures. In this review, we summarized the decades of investigations on a typical biological structure constructed by fiber aragonites in mollusk shells. Crossed-lamellar structure, as one of the most widespread structures in mollusk shells, reconciles the strength-toughness trade-off dilemma successfully due to the presence of highly-hierarchical architectures. This distinctive structure includes several orders of sub-lamellae, and the different order lamellae present a cross-ply feature in one macro crossed-lamellar layer. When a mollusk shell has more than one macro-layer, the crossed-lamellar structure exhibits various forms of architectures including 0°/90°, 0°/90°/0° typical-sandwich, 15°/75°/0° quasi-sandwich, and 0°/90°/0°/90° arranged modes. The fracture resistance and the relevant toughening mechanisms are directly related to the highly-hierarchical crossed-lamellar structures on different length scales. This article is aimed to review the different arranged modes of crossed-lamellar structures existing in nature, with special attention to their impact on the mechanical behavior and salient toughening mechanisms over several length scales, for seeking the design guidelines for the fabrication of bio-inspired advanced engineering materials that are adaptive to different loading conditions.

在数十亿年的进化过程中，自然界的生物拥有近乎完美的生存结构和功能。生物材料中多个长度尺度上的多尺度结构在实现结构和功能完整性方面起着关键作用。纤维作为自然界中常见的主要结构元素，可以通过不同的方式轻松构建，从而形成各种自然结构。在这篇综述中，我们总结了由软体石在软体动物壳中构建的典型生物结构的数十年研究。交叉层状结构作为软体动物壳中最广泛的结构之一，由于高度分层的结构的存在，成功地解决了强度-韧性之间的权衡难题。这种独特的结构包括几个顺序的亚片层，并且不同顺序的薄片在一个宏观的交叉薄片层中呈现出交叉层特征。当软体动物的壳具有一个以上的宏观层时，交叉层状结构会表现出多种形式的结构，包括0°/ 90°，0°/ 90°/ 0°典型三明治，15°/ 75°/ 0°准三明治-三明治和0°/ 90°/ 0°/ 90°排列模式。断裂强度和相关的增韧机制与不同长度尺度上的高度分层的交叉层状结构直接相关。本文旨在回顾自然界中存在的交叉层状结构的不同排列方式，并特别关注它们在多个长度尺度上对力学行为和凸显增韧机制的影响，