链段拉伸不均匀性对橡胶网络单轴失效响应的影响

摘要(中文译文)

橡胶态网络（如弹性体和的水凝胶）的宏观失效响应涉及单条聚合物链的断裂，而这一过程受网络拓扑结构的调控。然而，单链断裂事件如何导致宏观失效的确切机制仍知之甚少。本研究采用离散网络（Discrete Network, DN）模拟方法，研究模型随机网络在单轴拉伸下的失效机制。DN模拟结果表明，以宏观应力-拉伸响应急剧下降为特征的宏观失效，仅需网络中局部区域内一小部分链的断裂即可发生，即使在完美的单分散网络中亦然。局部失效由链拉伸中预先存在的非均匀性所触发，并进一步受链长或链强度等网络参数的调控。简单的橡胶弹性微观力学模型，如三链模型和八链模型，无法捕捉损伤的起始，因为它们未能捕捉链拉伸的非均匀性。更复杂的微球理论（包括仿射和非仿射版本）仅部分解决了这一缺陷。总体而言，本研究结果为橡胶态网络的失效机制提供了新的见解，同时为验证改进的本构理论提供了有价值的参考结果。

Abstract

The macroscopic failure response of rubbery networks such as elastomers and hydrogels involves the scission of individual polymer chains, mediated by the network topology. However, the precise mechanisms by which individual chain scission events result in macroscopic failure remain poorly understood. In this work, we use Discrete Network (DN) simulations to investigate failure mechanisms in model random networks in uniaxial tension. Our DN simulation results suggest that macroscopic failure, characterised by a sharp drop in the macroscopic stress-stretch response, only requires the scission of a small fraction of chains in a localised region of the network, even in perfect monodisperse networks. Localised failure is triggered by pre-existing heterogeneities in the chain stretch and is further modulated by network parameters such as the chain length or chain strength. Simple micromechanical models of rubber elasticity, such as the three-chain and eight-chain models, fail to capture the onset of damage because they do not capture the chain stretch heterogeneity. More sophisticated microsphere theories in their affine and non-affine versions only partially address this shortcoming. Overall, our results provide new insights into failure mechanisms of rubbery networks, while providing reference results useful for the validation of improved constitutive theories.

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