载荷与热、光复合作用下柔性高性能纤维的动态弯曲疲劳行为与失效机制

Flexible high-performance fibers have been widely used in extremely complex environment, showing excellent mechanical properties and stability to extreme environment. However, its plasticity and the tendency to original fine structure give rise to easy bending failure of the fiber, especially under the coupled effect of loading, thermal and light, and thereby obstacling its further applications. This project focuses on the bending fatigue performance of three flexible high-performance fibers (Kevlar49, PBO, high-strength polyethylene fiber) using a self-designed fixed point bending fatigue tester. The combined effect of temperature and light exposure on the bending fatigue of high performance fibers will be investigated in details. The bending fatigue life curves and the most sensitive factors of bending fatigue failure under thermal and light environment will be obtained. Mathematical models and finite element models will be built to understand the bending fatigue behavior of high performance fibers under thermal and light so as to estimate the bending fatigue life of these fibers. The invalidation evolution model of bending fatigue will also be constructed by in-situ and real-time observing the bending fatigue fracture processes and fracture morphologies of the fibers. The invalidation evolution mechanism and fracture mode will then be investigated. The invalidation micro-mechanism will be discussed by analyzing the micro-structure of fracture fibers. This project will benefit the safe and effective usage of high performance fibers in industry. It also provides basic theories for inhibiting the bending fatigue fracture and improving the environmental stability of high performance fibers.

柔性高性能纤维具有极好的力学和耐环境稳定性能，在极端环境下有广泛的应用，但由于原纤化与塑变性特征，易于弯曲破坏，尤其在载荷与热、光复合作用下更为严重。本项目以Kevlar49、PBO和高强聚乙烯三种柔性高性能纤维为研究对象，采用自行设计的定点弯曲疲劳测试装置研究载荷与热、光复合作用下三种纤维的弯曲疲劳行为，获取热、光作用下三种纤维的疲劳寿命曲线和疲劳破坏特征,提出纤维弯曲疲劳失效的敏感因素；构建热、光作用下纤维弯曲疲劳过程的数学模型和有限元模型，揭示纤维弯曲疲劳失效的力学机制及预测纤维的弯曲疲劳寿命；通过原位实时观测技术研究纤维弯曲疲劳破坏过程和断裂端形态，建立热、光环境下纤维弯曲疲劳失效演化模型，给出纤维弯曲疲劳演化机理和断裂模式，明晰纤维弯曲疲劳失效的微观机制。项目的实施将为高性能纤维的正确使用提供可靠保障，也为抑制高性能纤维的疲劳破坏和改善其耐环境稳定性提供理论依据。

本项目针对柔性高性能纤维易于原纤化与塑变性特征，易于弯曲破坏，在重复弯曲作用下纤维极易破坏，尤其在载荷与热、光复合作用下更为严重。项目以Kevlar49、PBO和高强聚乙烯三种柔性高性能纤维为研究对象，采用自行设计的定点弯曲疲劳测试装置研究不同载荷下纤维的弯曲疲劳破坏行为，也讨论了载荷与热、光复合作用下三种纤维的弯曲疲劳行为，获取热、光作用下三种纤维的疲劳寿命曲线和疲劳破坏特征,发现在高温和光照条件下三种纤维的弯曲疲劳寿命明显下降，提出纤维弯曲疲劳失效的敏感因素；并利用有限元构建热、光作用下纤维弯曲疲劳过程的数学模型，揭示纤维弯曲疲劳失效的力学机制及预测纤维的弯曲疲劳寿命，找到纤维最易破坏点；通过原位实时观测技术研究纤维弯曲疲劳破坏过程和断裂端形态，建立热、光环境下纤维弯曲疲劳失效演化模型，给出纤维弯曲疲劳演化机理和断裂模式，明晰纤维弯曲疲劳失效的微观机制。项目的实施将为高性能纤维的正确使用提供可靠保障，也为抑制高性能纤维的疲劳破坏和改善其耐环境稳定性提供理论依据。