【作者】 杨志贤；

【导师】 戴振东；

【作者基本信息】 南京航空航天大学 ， 机械设计及理论， 2009， 博士

【摘要】 本文以生活在三种不同生活环境(包括水环境、陆地环境、土壤环境)的9种甲虫为研究对象,从微结构、力学性能、鞘翅联接机制和鞘翅张合几何等方面对甲虫生物材料进行实验和微结构观测,并就实验结果进行对比分析和研究。结构上,鞘翅是非光滑表面,主要存在2种形貌:“犁沟状”条凸形貌和凹坑、凸苞分布形貌,鞘翅断面SEM实验表明鞘翅是一种中空型轻质生物复合材料,由鞘翅背壁层、中空夹芯层和腹壁层构成,而背壁层又是由黑色的致密外表皮层和数层纤维层相互交织后再铺设而成的内表皮层组成,实验得到甲虫鞘翅的比重(单位:kg/m~3)为0.8×10~3～0.9×10~3;东方龙虱前附足吸附脚掌上面布满“鞋形状”微型吸盘,侧缘长有许多微刚毛群,实验得到其最大法向吸附力53.3mN±7.68mN,最大切向吸附力213.5mN±33.53mN,猜测其吸附机制包含微吸盘的真空负压吸附和微刚毛群的Van der Waars力粘附两种。力学性能上,本文对9种甲虫鞘翅进行了纳米压痕实验和拉断实验,纳米压痕实验测定了鞘翅外表皮层的硬度和弹性模量参数值,结果由头部区域至尾部区域呈增大趋势,其力学性能呈现拓扑分布规律,经线性回归得到甲虫鞘翅力学参数值为:硬度0.335GPa±0.130GPa,弹性模量6.920GPa±1.461GPa,而东方龙虱鞘翅硬度为0.475GPa±0.089GPa,弹性模量为8.214 GPa±0.708GPa,分别为甲虫鞘翅平均值的1.41倍和1.19倍,该结果体现东方龙虱鞘翅力学性能较一般甲虫鞘翅优异;拉伸实验表明鞘翅的变形主要以弹性变形为主,鞘翅纵向强度极限要大于横向强度极限,实验得到新鲜鞘翅强度极限值(σb)169.2MPa～194.5MPa,其比强度为0.20～0.22(比强度定义为材料的强度极限σb除以材料的比重ρ),与超轻质镁锂合金相当(0.16～0.21)。联接机制方面,鞘翅采用了“楔形状”榫嵌入式联接机构,头部区域凸出榫片和楔形槽尺寸较小,尾部区域凸出榫片和楔形槽尺寸较大,其几何结构由头部至尾部呈线性增大,在鞘翅的凸出榫片端面均布满朝向一致的微刺突和微凸苞结构,该微结构主要加强鞘翅间的锁合联接,鞘翅的联接机制主要经由两个阶段:一是合翅联接过程,二是锁合联接过程。鞘翅张合机制方面,通过高速摄像机录制的鞘翅张合运动轨迹录像,分析甲虫鞘翅上标记点的三维轨迹来描述甲虫鞘翅的张合运动机制,得到甲虫鞘翅的张合运动机制为:绕经过小盾板位置的单轴的旋转运动;鞘翅仰角在30°～60°之间,甲虫为了最大限度地减少鞘翅在飞行当中的能量消耗而选择了最适应的角度,鞘翅的张合过程易于控制且节能、高效。综合上述,甲虫鞘翅是一种轻质、具高比强度和优异延塑性能的生物复合材料,该研究为航空航天领域对于轻质高强复合材料的设计提供仿生的生物学基础。更多还原

【Abstract】 In the dissertation, Morphological structures, mechanical properties, coupling mechanism and geometry of elytra opening and closing from 9 different beetles, which live in various environments (air, water, soil), were investigated.An analysis of the morphological structure indicates that the elytra have a non-smooth surface, containing two kinds of appearances: furrow surface or concave and convex surface, which can reduce adhesion and resistance present in surface contact. SEM photos of elytra sections show that the elytra are hollow and light-weight composite biomaterials, which consist of a compact dorsal side, a hollow section and a ventral side. The dorsal side consists of black compact epicuticle and looser exocuticle formed from some fibre layers complexed with each other in a parallel way, a positive-negative way and a helical way. The elytra’s density (in kg/m~3) was tested and shown to be 0.8×10~3～0.9×10~3. The morphology of the Cybister adhesive fore-foot was observed under SEM, and it was shown that lots of micro-discs functioning as a shoe are distributed on its surface and lots of setae are distributed on its marginal side. The maximal normal force is 53.3mN±7.68mN and the maximal tangential force is 213.5mN±33.53mN. It is estimated that the vacuum adsorption of the micro-discs, together with the van der Waals adhesion of the setae, produce the ultimate adhesive forces of a single adhesive foot.Regarding mechanical properties, a Nano-indenter Test and a Tensile Test were carried out on different beetles’elytra to investigate its mechanical properties and tensile intensity. Results show that the mechanical properties of elytra increase gradually from the cephalosome zone to the empennage zone, which presents topological distribution. The hardness and modulus of beetles’elytra were taken from the results of the Nano-indenter and Tensile tests through linear regression and the average values were 0.335GPa±0.130GPa and 6.920GPa±1.461GPa, respectively. Cybister’s results were 0.475GPa±0.089GPa and 8.214GPa±0.708GPa, respectively, which is 1.41 and 1.19 times that of beetles’elytra, respectively. Thus, this confirms conclusively that Cybister elytra have a much more excellent performance compared to that of beetles’elytra. Tensile Test results indicate that the distortion of beetles’elytra is largely elastic, while the longitudinal stress to fracture is larger than the transverse one. The stress to fracture of fresh elytra (σ_b) is 169.2MPa～194.5MPa; the specific intensity is 0.20～0.22 (the specific intensity is defined asσ_b toρ). Compared to the Mg-Li alloy (0.16～0.21), fresh elytra have a high specific intensity.Regarding its coupling mechanism, beetles’elytra are conjugated with each other via the cuneal tenon carving into the mortise. The dovetail and mortise are short and thick in the cephalosome zone and become longer and thinner in the empennage zone. There are some spinules oriented in the same way and convex buds emerging into the surface of the dovetail surface. These micro-structures help to lock two elytra tightly together. Coupling of elytra is accomplished via the following two steps: the first is the coupling process of elytra; the other is the locking process of elytra.On geometry, the mark’s 3D-tracks marked on the elytra apex were analyzed with special software from beetles’elytra flight videos via a high speed camera to explain the geometry of beetles’elytra opening and closing. Previous research has shown that the geometry of elytra opening and closing in some beetles are a planar rotation around a single axis across the scutellum. The elevated angle of elytra in opening is 30°～60°. Beetles choose an adaptive angle to adequately reduce energy use during flight. This indicates that the coupling mechanism of elytra permits rotation to be easily controlled while the process spends less energy and works more effectively.In conclusion, beetles’elytra are light-weight composite biomaterials with a high ratio of intensity to weight, high stress to fracture and excellent flexibility. The results of this work offer biomimetic reference for designing future light-weight, high intensity composites for use in aeronautics and astronautics industry.更多还原