Abstract The welding of thermosetting polymers is a longstanding challenge in polymer science and engineering. Recently, developed dynamic covalent polymers (also known as vitrimers) provide a promising strategy for achieving interface welding. An understanding of the fundamental physical mechanisms underlying interfacial welding and fracture behavior is critically required to thoroughly explore the full potential of this technique. To this end, in this paper, we develop a chemo-mechanical fracture model to account for the toughness of the welding interface in vitrimers. The evolution of the interfacial vitrimer network microstructure in the welding is modeled by using a bamboo joint-like structural model. Based on the evolution of the network structure, the fracture toughness of the welding interface is formulated by integrating the dissipated strain energy in the cohesive region ahead of the interfacial crack, in which a shape function with an exponential form is proposed to describe the strain profile of the vitrimer networks. Our theoretical model also correlates interfacial fracture toughness with welding temperature and time. An optimal range of welding temperature to time is identified to achieve a higher toughness of the welding interface. We show that a larger cohesive region induced by enhancing the vitrimer network structure results in an elevated interfacial fracture energy. The results predicted by our model are in good agreement with the relevant experimental measurements. This work might help to decipher the toughening mechanisms for the welding interface of vitrimers.

中文翻译：

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玻璃体焊接界面的化学机械断裂模型

摘要 热固性聚合物的焊接是聚合物科学和工程中长期存在的挑战。最近，开发的动态共价聚合物（也称为玻璃体）为实现界面焊接提供了一种有前途的策略。为了彻底探索该技术的全部潜力，迫切需要了解界面焊接和断裂行为背后的基本物理机制。为此，在本文中，我们开发了一种化学机械断裂模型来解释玻璃体中焊接界面的韧性。焊接中界面玻璃体网络微观结构的演变通过使用竹节状结构模型进行建模。基于网络结构的演化，焊接界面的断裂韧性是通过积分界面裂纹前内聚区中耗散的应变能来计算的，其中提出了一个指数形式的形状函数来描述玻璃体网络的应变分布。我们的理论模型还将界面断裂韧性与焊接温度和时间相关联。确定焊接温度与时间的最佳范围以实现焊接界面的更高韧性。我们表明，通过增强玻璃体网络结构引起的更大的内聚区域导致界面断裂能升高。我们的模型预测的结果与相关的实验测量结果非常吻合。这项工作可能有助于破译玻璃体焊接界面的增韧机制。