化学退化作用下质子交换膜力学性能及本构模型研究

Fuel cell is a clean and efficient energy conversion device. It has a very broad application prospect in the field of traffic power. Proton exchange membrane (PEM) is the core component of fuel cell and the durability of PEMs is a critical factor limiting the application and promotion of fuel cells. Investigations have shown that the durability of PEMs is coupled by mechanical stress and chemical degradation. However, there is little research on the mechanism and rule of force-chemical coupling of PEMs. In this project, the degree of chemical degradation will be performed by micro-mesoscopic-macro characterization methods firstly. The performance degradation mechanism of PEMs under chemical degradation will be clarified. The creep, fatigue fracture properties and uniaxial/multiaxial cycle performance of PEMs will be explored after chemical degradation. The failure mechanism of PEMs will be revealed through these investigations. Subsequently, the damage variable will be introduced and embed in the rule of flow, kinematic hardening and isotropic hardening. The effects of chemical degradation will be quantified and a cyclic viscoelastoplasticity constitutive model considering chemical degradation will be established. Thus, the model will accurately describe and predict the stress-strain response of PEMs before and after chemical degradation. In summary, this project will gain a scientific understanding of the durability of PEMs from the perspective of force-chemical coupling and provide theoretical guidance and support for PEMs' optimized design and durability assessment.

燃料电池是一种清洁、高效的能量转换装置，在交通动力领域具有非常广阔的应用前景。质子交换膜是燃料电池的核心部件，其耐久性是制约燃料电池应用和推广的关键因素。研究表明，质子交换膜的耐久性会受到机械应力和化学退化的耦合作用，但是目前对于其力-化耦合作用的机理和规律却鲜有研究。因此，本课题首先将对质子交换膜的化学退化程度进行微观-介观-宏观多尺度表征，澄清化学退化作用下质子交换膜的性能劣化机制，探究化学退化后蠕变、疲劳断裂性能和单轴/多轴循环性能的变化规律，揭示失效破坏机理。随后，本课题拟通过引入损伤变量，并将其嵌入流动律、随动强化律和各向同性强化律中，以量化描述化学退化的影响，建立考虑化学退化的循环粘弹塑性本构模型，从而精确描述和预测质子交换膜在化学退化前后的应力-应变响应。综上，本课题将从力-化耦合的角度获得对质子交换膜耐久性的科学认识，为质子交换膜的优化设计和耐久性评估提供理论指导和支撑。

作为燃料电池的核心部件，质子交换膜的主要功能包括传导质子、分离燃料和氧化剂、为催化剂提供物理支撑以及隔离电子。质子交换膜的机械完整性是燃料电池长期运行的根本保证。影响质子交换膜的耐久性的因素主要包括化学降解和机械降解。因此，研究化学退化作用下质子交换膜的力学性能，将更加贴近燃料电池实际工况。本项目主要研究内容包括：（1）开展了质子交换膜不同化学退化程度的多尺度表征研究，澄清了化学退化后质子交换膜的劣化机制，为理解力学性能变化奠定了基础；（2）通过试验研究了化学退化后质子交换膜的拉伸性能、循环性能和断裂性能演化规律；（3）发展了基于图像处理的质子交换膜裂纹扩展识别技术，提高了测试效率；（4）开展了质子交换膜多轴胀形力学性能试验研究，研究了不同温湿度和气压条件下的失效规律；（5）建立了考虑化学退化的循环粘弹塑性本构模型，对蠕变恢复试验、单轴棘轮试验、双轴多路径棘轮变形、双轴蠕变试验结果进行了较合理的预测。本项目从力-化耦合的角度获得了对质子交换膜耐久性的科学认识，将为质子交换膜的优化设计和耐久性评估提供理论指导和数据支撑。