The Morone saxatilis, as a common teleost fish originating from the northern Atlantic Ocean, have a spiny posterior margin and are comprised of two main layers: a bony organic external layer and an internal layer of collagen. The ctenoid scales are staggered and cover most of the body of the fish, providing a continuous barrier to penetration and flexural compliance. A detailed analysis of the imbricate pattern of ctenoid scales revealed that each scale overlaps with six other adjoining scales (Figure 7). Although the arrangement of the scales is such that any point on the surface of the fish is covered by three overlapping scales, the scale diameter is not uniform along the length of the ...view middle of the document...
Furthermore, they found that the puncture resistance of individual scales is important as well as their overlap and their arrangement to provide efficient protection. They examined the effect of three different scale arrangement (stacked, staggered, and rotated) on overall puncture performance to investigate how the assemblage of scales operates as armor. It is found that the stacked scales had the highest puncture resistance, as shown in Figure 8c .
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2.2. Mollusk shells
2.2.1. Otala lactea
Mollusk shells, as the most common marine species protection structures, are primarily composed of a brittle material (calcium carbonate). These biological composites which exhibits an attractive combination of stiffness, strength and toughness, provide remarkable protection against environmental factors [27-33]. The microstructural investigation of the mollusk shells and in specific Otala lactea shell showed that these biocomposites has a three-layered microstructure (Figure 9b). Each layer is composed of numerous sublayers which are called first-order lamellae and have a thickness of about 5–17 µm. The first-order lamellae themselves are divided into a large number of parallel second-order lamellae with 4–6 µm thickness. Moreover, each second-order lamella consists of needle-shaped aragonite crystals which are called third-order lamellae (Figure 9c,d).
Quasi-static analysis of O. lactea shell showed that the complex geometry and substantial curvatures of the shells play important roles in enhancing the efficiency of the shell through the minimization of the stress concentration at the position of the applied force. It is interesting to note that when the snail shell is under an external compressive force in axial direction, a high proportion of the applied force is carried by the columella. Indeed, the existence of the columella leads to increase in the resistance of the mollusk shells without failure, especially when the external force is applied in the axial direction .
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2.2.2. Abalone shell
The abalone shell, which belongs to a class of mollusks called gastropoda, has a low open spiral structure. The hierarchical structure of abalone shell is illustrated in Figure 10. The thick inner layer of the shell is composed of nacre, an organic-inorganic composite material produced by some mollusks. As can be seen from Figure 10, the first level is mesolayers with a thickness of ∼300 µm, separated by ∼20 µm organic. The structure of nacre within the abalone shells is composed of “brick-like” tiled hexagonal platelets of aragonite (8-12 µm in length and 0.5 µm thick), which arranged in a continuous parallel lamina. Aragonite (orthorhombic calcium carbonate) is metastable at low pressures (lower than 0.4 GPa) and grow in the c-axis alignment normal to the plane of the tiles. The tiles held together by a 10-50 nm layer of an organic biopolymer of chitin and proteins (5 wt.%) and by mineral bridges. It is found that...