基于分子动力学的恶劣环境下 FRP 加固混凝土结构粘结界面失效机理研究

Due to the detrimental environmental exposure, the concrete structure deteriorates during the intended service-life, and the consequent structural failure could cause the personal injury and property damage. With the outstanding mechanical properties, the fiber reinforced polymer (FRP) has been widely used for the repair and strengthening of the deteriorated structure. Previous studies have indicated that the FRP-bonded concrete structure deteriorates under the harsh environments, where the critical failure region shifts from the concrete structure to the interface between the concrete and epoxy adhesive, which significantly weakens the durability of the bonded system. Currently, little is known about the failure mechanism of the FRP-concrete system under the various environmental exposures, especially the property deterioration of the bonded interface. The objective of this project is to investigate the fundamental failure mechanism of the FRP-bonded concrete system under the harsh environment at the microscopic level, with the focus on the deterioration of the bonded interface. Specifically, by using the molecular dynamics simulation method, the microscale interface model of the concrete-epoxy bonded system is constructed, which is subjected to various harsh environmental exposures to examine the change of its structure and adhesion energy. Meanwhile, the fracture testing is carried out on the macroscale sample to validate the failure mechanism as observed in the simulation. This research project will form the basis for understanding the long-term durability of the FRP-bonded concrete structure by considering the effect of the harsh environment, which will significantly contribute to the scientific knowledge in the area of the structural durability and interfacial integrity of the FRP-bonded system, and advance the application of the FRP composite in the civil engineering field.

由于环境侵蚀，混凝土结构在服役过程中会出现一定程度的破坏，其结构失效将造成生命财产损失。凭借优越的力学性能，纤维增强复合材料（FRP）被广泛应用于受损结构的加固。研究表明，恶劣环境下FRP加固混凝土结构会发生退化，关键破坏部位从正常情况下的混凝土内部转变为混凝土与环氧树脂的粘结界面，从而危害加固结构的服役安全。目前，对恶劣环境下此加固结构的失效机理，特别是粘结界面的性能退化所知甚少。本课题研究目的是在微观层面揭示恶劣环境下FRP加固混凝土结构的失效机理，重点关注粘结界面的退化。为此，采用分子动力学模拟方法，建立混凝土与环氧树脂界面的微观结构模型，研究不同环境下此界面分子结构和粘结性能的变化。同时，通过宏观尺度的加载实验验证此结构失效机理。本课题为恶劣环境下FRP加固结构的服役安全这一关键问题提供重要基础，促进此加固结构的可靠性、耐久性等领域科学知识发展，推动FRP在土木工程中的应用。

凭借优越的力学性能，纤维增强复合材料（FRP）被逐渐应用于受损混凝土结构的加固。然而，恶劣环境下FRP加固混凝土结构会发生混凝土与FRP界面的脱粘失效，以混凝土与环氧树脂的界面为关键破坏部位，从而危害加固结构的服役安全。本项目通过宏观尺度的加载实验，研究了混凝土与FRP粘结界面在不同制备条件下的粘结特性与失效过程。同时，采用分子动力学模拟方法，构建了切合实际的树脂、FRP中纤维/树脂界面以及混凝土中水化硅酸钙/树脂界面的分子模型，成功的预测了这些材料在纳米尺度的结构特征与力学性能。基于分子动力学模型，研究了恶劣环境，特别是潮湿环境下树脂、纤维/树脂界面以及水化硅酸钙/树脂界面的微观分子结构随水分含量等化学组分的演变规律，揭示了微观分子结构与性能的对应关系。其中，重点研究了水分子与树脂的交联聚合结构、与纤维/树脂界面以及与水化硅酸钙/树脂界面的相互作用与反应，探明了水分子对于FRP加固混凝土结构中水化硅酸钙/树脂粘结界面的破坏机制。本项目为解决恶劣环境，特别是潮湿环境下FRP加固混凝土结构的服役安全这一关键问题提供了重要的理论基础，为混凝土与FRP粘结界面的耐久性预测提供了科学的指导。