Flexible network materials with periodic constructions of bioinspired wavy microstructures are of focusing interest in recent years, because they combine outstanding mechanical performances of low elastic modulus, high stretchability, biomimetic stress-strain responses, and strain-limiting behavior. In practical applications (e.g., bio-integrated devices and tissue engineering), small holes are often strategically designed in flexible network materials to accommodate functional chips and other individual electronic components. The design of imperfection insensitive flexible network materials is therefore of pivotal importance. While random structural constructions are believed to play crucial roles in the excellent mechanical properties of many biological materials, the effect of randomness on mechanical performances of flexible network materials has not yet been explored. In this work, a class of two-dimensional (2D) flexible random network materials consisting of horseshoe microstructures is introduced. Their node distance distributions, which can be characterized by a parameter related to randomness, follow well the Weibull probability density function. Combined numerical and experimental studies were performed to elucidate the effect of randomness on nonlinear mechanical responses of flexible network materials. Simple analytical equations are obtained for their key mechanical properties (e.g., strength, stretchability, and initial modulus). Flexible random network materials (with randomness ≥ 0.4) were found to exhibit approximately isotropic J-shaped stress-strain responses, even in the high-strain regime. Finally, we study the reduction of stretchability and strength in random network materials induced by different types of imperfections (e.g., a missing filament, a missing node, or many missing filaments). In comparison to periodic network materials, random network materials (e.g., with randomness ≥ 0.6) show much smaller reductions of stretchability/strength when the imperfection appears, and are therefore more imperfection-insensitive. Such an imperfection-insensitive behavior can be mainly attributed to a relieved stress concentration around the imperfection of random network materials.

中文翻译：

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具有马蹄形微结构的不敏感缺陷不敏感柔性随机网络材料


近年来，具有生物启发波浪形微结构周期性结构的柔性网络材料引起了人们的关注，因为它们结合了低弹性模量、高拉伸性、仿生应力-应变响应和应变限制行为的出色机械性能。在实际应用（例如，生物集成设备和组织工程）中，通常在柔性网络材料中战略性地设计小孔，以容纳功能芯片和其他单个电子元件。因此，不完美、不敏感的柔性网络材料的设计至关重要。虽然人们认为随机结构在许多生物材料的优异机械性能中起着至关重要的作用，但随机性对柔性网络材料力学性能的影响尚未得到探索。在这项工作中，介绍了一类由马蹄形微结构组成的二维 （2D） 柔性随机网络材料。它们的节点距离分布（可以用与随机性相关的参数来表征）很好地遵循 Weibull 概率密度函数。进行了数值和实验相结合的研究，以阐明随机性对柔性网络材料非线性力学响应的影响。获得了其关键机械性能（例如强度、拉伸性和初始模量）的简单解析方程。发现柔性随机网络材料 （随机性≥ 0.4） 即使在高应变状态下也表现出近似各向同性的 J 形应力-应变响应。最后，我们研究了由不同类型的缺陷引起的随机网络材料中的拉伸性和强度降低（例如、缺少细丝、缺失节点或许多缺失细丝）。与周期性网络材料相比，随机网络材料（例如，随机性≥ 0.6）在出现缺陷时表现出的可拉伸性/强度降低幅度要小得多，因此对缺陷更敏感。这种对缺陷不敏感的行为主要归因于随机网络材料缺陷周围的应力集中减轻。