As a natural defensive structure, insect cuticle exhibits fascinating impact resistance properties in their body protection due to their spatial hierarchical architecture and the stiffness distribution along their thickness designed by nature. In this study, inspired by the pattern of insect cuticle, we present a novel design strategy of graded elastic ring systems with programmable stiffness gradients to enhance the protective properties. By studying the influence of the elastic modulus, radius and thickness of rings on the impact response of the bio-inspired graded ring systems, the optimal solution of programing the stiffness gradient can be obtained. The mechanical analyses of the single-column ring systems and the bio-inspired ring array architectures with different stiffness gradients under impact loading show that both the distributions of stiffness gradients along the impact direction and the concavity and convexity of the stiffness profiles have a great influence on preventing stress wave propagation and improving impact-tolerance. Compared with convex stiffness gradients, the concave stiffness gradients significantly improve the protective properties as well as reduce the peak value of collision force applied to inner structures. In concave stiffness gradients, the results show that the bio-inspired ring array architectures with exponential (EXP) stiffness gradient have been identified to result in the minimum values of stress, collision force and impulse under impact loading. The strategy proposed in this paper greatly improves the impact resistance property and defensive effect compared with that of the case without protection. The knowledge gained from this work will inspire the designs of novel advanced reusable and lightweight protective structures with improved impact resistance capability by programming reasonable stiffness distributions.

作为一种天然的防御结构，昆虫角质层由于其空间层次结构和自然设计的沿厚度分布的刚度分布，在其身体保护中表现出迷人的抗冲击性能。在这项研究中，受昆虫角质层模式的启发，我们提出了一种具有可编程刚度梯度的分级弹性环系统的新设计策略，以增强保护性能。通过研究环的弹性模量、半径和厚度对仿生梯度环系统冲击响应的影响，可以得到刚度梯度编程的最优解。冲击载荷作用下不同刚度梯度的单柱环系统和仿生环阵列结构的力学分析表明，沿冲击方向的刚度梯度分布和刚度剖面的凹凸有很大影响。防止应力波传播和提高耐冲击性。与凸刚度梯度相比，凹刚度梯度显着提高了保护性能，并降低了施加到内部结构的碰撞力峰值。在凹刚度梯度中，结果表明，具有指数 (EXP) 刚度梯度的仿生环形阵列结构已被确定为在冲击载荷下产生最小的应力、碰撞力和冲量值。本文提出的策略与没有保护的情况相比，大大提高了抗冲击性能和防御效果。从这项工作中获得的知识将通过对合理的刚度分布进行编程来激发具有改进抗冲击能力的新型先进的可重复使用和轻量级保护结构的设计。