草鱼鳞片的多级结构及力学性能

经过长时间的自然进化,硬骨鱼鳞片变得超薄、超轻,并具有很好的柔韧性。为研制新型柔性防护体系,对草鱼鳞片的多级结构及力学性能进行了研究。首先,按3个不同方向(0°、45°和90°)在鳞片中心区域裁取鳞片和胶原层2组试样;然后,进行了轴向拉伸测试并对不同含水量的鳞片以及不同应变率下鳞片和胶原层的力学性能进行了对比研究。结果显示:草鱼鳞片主要由坚硬的骨质外层和软质的胶原层组成,其中胶原层由胶原纤维层交错叠加组成,交错角约为28°~31°;鳞片的力学性能为平面内各向异性,而胶原层的力学性能为各向同性;脱水鳞片的弹性模量和拉伸强度显著增加,分别约为饱水鳞片的10倍和3倍,但极限应变减少了约50%。饱水鳞片和胶原层的力学性能与应变率有很大相关性。所得结论为新型仿生复合材料及柔性防护体系的研究提供了思路。 

Hierarchical structure and mechanical properties of scales from grass carp

During the long-term natural evolution, the scales of teleost fish become ultra-thin and ultralight, and have excellent flexibility. In order to develop an innovative flexible protection system, the hierarchical structure and mechanical properties of scales from grass carp were investigated. Two types of samples for scales and collagen layers were extracted from the central regions of scales by three different orientations (0°, 45° and 90°) firstly. Then, tensile tests in uniaxial were conducted and mechanical properties of scales with different water contents as well as scales and collagen layers under different strain rates were investigated comparatively. The result shows that the scales of grass carp consist of outer hard bony layer and inner soft collagen layer, and the collagen layer consists of twisted overplayed collagenous fiber lamellas whose spiral angles are about 28°-31°. The mechanical properties of scale are in-plain anisotropic, while the mechanical properties of collagen layer are isotropic. The elastic modulus and tensile strength of dehydrated scale increase significantly, which are about 10 times and 3 times of those of hydrated scale, while the ultimate strain reduces by about 50%. The mechanical properties of hydrated scale and collagen layer are highly dependent on strain rate. The conclusions obtained provide ideas for the investigation of bio-inspired innovative composites and flexible protection systems.