In nature, many insects have evolved hard cuticles to shelter their soft body, which is thought to be the “body-armour” for insects to protect against predators' sharp teeth or dynamic load damage caused by harsh environments. In recent years, researchers have found that the “body-armour” is composed of multi-layer materials with different elastic modulus from inside to outside. The gradient change rule of the formed material modulus reflects the evolutionary history of insect cuticle's adaptation to externa changes. In this article, the mechanical properties of spatial hierarchical architecture of insect cuticle, especially for the shield-like beetle elytra under impact loading, was investigated to reveal the impact resistance strategy and in-depth mechanisms of crashworthy protection. The results show that both discontinuity at the cuticle layers interface and the distributions of stiffness gradients through layers’ thickness have a great influence on preventing stress wave propagation and improving impact-tolerance. Insect cuticle such as beetle elytra with discontinuous exponential stiffness gradient (DC-EXP) along the thickness has been identified to result in the minimum values of stress and interaction force under impact loading, which leads to the best impact resistance property and defensive effect. Furthermore, we compared and discussed the protective properties of insect elytra with different sclerotized endocuticle under quasi-static compression and impact loading, respectively. The knowledge gained from this work reveals the advantages of nature’s choice of the stiffness distribution and may serve to inspire further research of developing advanced multifunctional structures with improved impact resistance capability by programming reasonable stiffness distribution.

在自然界中，许多昆虫已经进化出坚硬的角质层来掩盖其柔软的身体，这被认为是昆虫的“防弹衣”，可以防止捕食者的尖锐牙齿或恶劣环境造成的动态负载破坏。近年来，研究人员发现，“装甲”由多层材料组成，其内部和外部具有不同的弹性模量。形成的材料模量的梯度变化规律反映了昆虫角质层对外部变化的适应的进化历史。本文研究了昆虫表皮的空间层次结构的力学性能，特别是冲击载荷下的盾状甲壳虫的机械性能，以揭示其抗冲击性策略和防撞保护的深入机理。结果表明，表皮层界面的不连续性和整个层厚度的刚度梯度分布都对防止应力波传播和提高耐冲击性有很大影响。沿厚度方向具有不连续的指数刚度梯度（DC-EXP）的甲壳虫等昆虫角质层被确定为在冲击载荷下产生最小的应力和相互作用力，从而获得最佳的抗冲击性能和防御效果。此外，我们在准静态压缩和冲击载荷下，分别比较和讨论了不同硬化硬皮表皮昆虫鞘翅的保护特性。