目的 系统揭示PEEK材料在高速拉伸载荷下的颈缩与应变硬化行为,为其在复杂服役环境下的长期稳定应用提供指导。方法 采用Victrex 450G PEEK材料,在不同拉伸速率（10~900 mm/min）、温度（25 ℃及90 ℃）以及初始结晶度（21.6%、32.3%、35.2%）条件下进行材料单轴拉伸实验,通过数字图像相关技术获取标距段全场应变分布,实现局部颈缩及二次颈缩的定量分析,并对应变硬化起始点和应变硬化模量进行表征。结果 PEEK的单轴拉伸力学行为受温度及拉伸速率的显著影响,而初始结晶度对其影响有限。在25 ℃下,低速拉伸呈现单调硬化,高速拉伸则出现多级应力峰及二次颈缩现象,次级应力峰与局部应变集中高度相关;随拉伸速率增加,应变硬化起始点增加,应变硬化模量升高;当升温至90 ℃后,多级应力峰现象减弱,且在中高速拉伸速率下出现应力震荡现象,其幅度的增加随速率呈先增强后减弱的规律。结论 PEEK在高速拉伸下表现出强化的应变硬化与典型的二次颈缩特征,表明其在极端服役条件下的力学响应机制复杂,这对理解其结构可靠性及服役性能具有重要意义。
Abstract
The work aims to systematically reveal the necking and strain-hardening behavior of PEEK under high stretching velocities, to provide insights into its long-term stability in complex service environments. Uniaxial tensile tests were performed on Victrex 450G PEEK at various stretching velocities (10-900 mm/min), temperature (25 ℃ and 90 ℃), and initial crystallinity (21.6%, 32.3%, and 35.2%). Full-field strain distributions in the gauge section were obtained using digital image correlation (DIC), enabling quantitative analysis of local necking and secondary necking, as well as characterization of the onset of strain hardening and the strain hardening modulus. Results showed that the uniaxial tensile mechanical behavior of PEEK was significantly affected by temperature and tensile rate, while the initial crystallinity had a limited influence on it. At 25 ℃, PEEK exhibited monotonic hardening under low stretching velocities, while multiple stress peaks and secondary necking appear at high stretching velocities, with the secondary peaks strongly correlated with localized strain concentration. With the increase of the stretching velocity, the onset of strain hardening shifted to higher strains, and the strain hardening modulus increased. At 90 ℃, the multiple stress peaks were attenuated, and stress oscillations occurred at intermediate to high stretching velocities, with amplitudes showing a “first increasing, then decreasing” trend. In conclusion, under high stretching velocities, PEEK exhibits enhanced strain hardening and secondary necking, indicating a complex mechanical response mechanism under extreme service conditions. This finding is of great significance for understanding its structural reliability and service performance.
关键词
聚醚醚酮 /
半结晶聚合物 /
颈缩 /
应变硬化
Key words
poly-ether-ether-ketone (PEEK) /
semi-crystalline polymer /
necking /
strain hardening
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基金
国家自然科学基金（52175350,52475382）
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