天然和仿生柔性生物结构的设计

自然界中生物材料表现出的力学性能与其结构设计形式紧密相关。柔性生物材料多为多级结构设计，其独特的功能梯度特征使其具备优异的变形能力及良好的断裂韧性。本文借鉴工程结构设计基本单元的思想提出柔性结构仿生元素理念，根据几何形态将结构仿生元素分为：线元素、梁元素、柱元素、板壳元素、薄膜元素及组合元素。根据系统论的观点建立仿生柔性结构设计体系，归纳总结出柔性仿生结构的设计准则，并基于鱼鳞梯度结构设计新型仿生功能梯度板。通过有限元的方法对功能梯度板归一化自然频率进行分析。结果表明，类鱼鳞功能梯度板具有柔韧性及刚度软化特性。阐述了仿生柔性结构的设计方法，包括模仿设计、组合设计及选择匹配设计。

Study on the design of natural and biomimetic flexible biological structures

The mechanical properties of biomaterials are closely related to their structural design in nature. The flexible biological materials mostly are designed as hierarchical structure that has the unique feature of gradient, which makes the materials have good deformation capacity as well as toughness. In this paper, the concept of bioinspired flexible structural elements was put forward that based on the basic elements of engineering structural design. The bionic elements were divided into line elements, beam elements, column elements, plate and shell elements, thin film elements and composite elements according to the geometrical morphology. The design system of bioinspired flexible structure was developed from the point of view of system theory. The design criterion of flexible bionic structure was summarized. A novel bionic functionally gradient plate was design based on the gradient structure of fish scale. The normalized-dimensionless natural frequencies of functionally graded plate were computed by the finite element method, the results show that the functionally graded plate, inspired by the structure of fish scale, has the characteristics of flexibility and stiffness softening. Finally, the natural function of flexible biomimetic methods is discussed in detail, including imitation design, combinatorial design and matching design.