蜘蛛网丝作为典型的天然生物材料，不仅有优异的材料力学性能，而且在粘附猎物方面有独特的力学机理。深入理解蜘蛛网丝粘附猎物背后的物理机制，对帮助理解蜘蛛在自然界中适应生存具有重要意义，对工程网络结构的设计也具有启示作用和应用价值。本文通过实验测量、数值模拟和理论分析，研究了蜘蛛网丝粘附猎物背后的力学机理。首先，本文通过实验研究，对蜘蛛网全网蜘蛛丝的力学性能进行了实验测量，获得了包括径向丝和环向丝在内的全网蛛丝的力学性能数据。通过对数据的统计分析，发现了径向丝的力学性能在全网有较为均匀的分布，而环向丝的力学性能沿着径向呈现出明显的梯度变化规律。采用Fung超弹性本构模型对环向丝的应力应变曲线进行拟合，并分析其力学性能的变化范围，发现了全部环向丝的弹性模量有近300倍的变化，硬化参数也有近30倍的变化。通过有限元模拟分析，揭示了力学性能呈梯度分布的环向丝在蜘蛛网能量吸收上的优化作用。其次，本文提出了蜘蛛网丝粘附猎物的力学模型。通过实验和理论分析，研究了蜘蛛丝和粘性胶滴的协同粘附行为，对蜘蛛丝与猎物的脱粘过程进行了分析。实验发现蜘蛛丝在粘附猎物过程中存在三个阶段，同时分析了不同阶段对猎物粘附所起的作用；研究了蛛丝模量和胶滴强度对蛛丝粘附性能的影响，探讨了蛛丝–基体系统对猎物能量吸收的规律；研究了蜘蛛丝对不同尺寸猎物的粘附规律，发现蜘蛛丝在粘附猎物时具有对猎物尺寸不敏感的特性；通过量纲分析和数值计算，建立了蜘蛛丝粘附的能量吸收标度律，并发现了蛛丝模量与胶滴强度的最优匹配关系。最后，本文探讨了不同因素在蜘蛛网丝粘附中的影响。讨论了胶滴强度和胶滴间距对粘附性能的影响，发现了蜘蛛网丝存在粘附鲁棒性；关注蜘蛛丝力学性能在粘附中的影响，讨论蜘蛛丝的本构关系对粘附性能的影响；研究猎物粘附位置和逃生角度对蛛网粘附能力的影响，揭示了多根蜘蛛丝对猎物协同粘附的影响规律。
As a typical natural biological material, silks from spider orb web possess exquisite geometric structures and excellent mechanical properties, and thus endow unique mechanical properties in prey adhesion. It is of great significance to understand the physical mechanism behind spider web silk’s adhesion, which would help to understand the survival of spiders in nature, and has important enlightenment and application value to the development and practice of modern net structure.First, the mechanical properties of all the spider silks in an orb web were measured experimentally, and the mechanical properties of radial silks and spiral silks were obtained. Through statistical analysis of the experimental data, it is found that the mechanical properties of the radial silks are uniformly distributed in the whole orb web, while the spiral silks feature distinct spatial gradient variations along the radial direction of the web. Fung hyper-elastic constitutive model was used to fit the stress–strain curves of all the spiral silks, and it is found that the elastic moduli of all the spiral silks change nearly 300 times, while the constitutive nonlinearity also varies nearly 30 times. Finite element simulation was used to investigate the energy absorption mechanisms of spider webs, and found that the gradient effect of mechanical properties of spiral silks can significantly enhance the energy absorption and structural integrity of the web.Second, an adhesion mechanics model of spider silks in orb webs was proposed. Synergistic adhesion behavior of spider silk and glue droplets was studied via both experiments and theoretical analysis. The peeling-induced detachment between a spider capture silk and prey was analyzed, and three typical stages during the peeling process were found, which gave silk different strategies to capture preys with different sizes and weights. We examined the synergistic effect between silk modulus and glue stickiness, as well as the energy absorption capability of the silk–substrate system when adhered to objects. Energy absorption capability to capture preys items of different sizes was studied and we found the silk is insensitive to prey items of different sizes when catching preys. Through dimensional analysis and theoretical analysis, we derived a scaling law to determine the optimal value of energy absorption with different silk’s elastic modulus and glue strength. For a given adhesion strength of the glue droplets, there exists an optimal elastic modulus of the silk to maximize the energy absorption during peeling.Finally, the adhesion mechanics model of spider silks in orb webs was used to research the different influence factors on spider capture silk’s adhesion. Spider silks exhibit a high level of robustness in the sense that both the total adhesion strength and energy absorption capacity are insensitive to the random adhesion strengths between its glue droplets and the prey. The constitutive parameters of spider silks can affect the adhesion capacity, via both the elastic modulus and the nonlinearity. The locations of contact zone and the directions of the load applied can affect the adhesion capacity of the silks. In addition, the adhesion mechanics model can also research the case when a prey was adhered to a plurality of spider silks.
