Effects of temperature and strain rate on hardening behavior of carbon fiber reinforced polyether ether ketone composite under shear load
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摘要: 碳纤维增强聚醚醚酮(CF/PEEK)是一种高性能热塑性复合材料,在航空航天领域有着广阔的应用前景。由于PEEK具有温度和应变率相关的非线性行为,导致CF/PEEK复合材料在基体主导的面内剪切方向也有类似的力学行为。本文在不同的温度和应变率下对CF/PEEK复合材料试件进行了剪切实验,将应力-应变曲线分为线性与非线性部分,发现温度和应变率对CF/PEEK复合材料的屈服应力有着较大的影响。随着温度从20℃升高到130℃屈服应力下降了66%左右,下降速度先快后慢,随着应变率从10−5 s−1提高到0.1 s−1屈服应力均匀增大了35%左右。将所得规律拟合背应力经验公式,修改了经典的热塑性复合材料本构模型的屈服函数。并编写VUMAT用户子程序对CF/PEEK复合材料剪切实验进行数值分析,与实验结果对比发现非线性阶段的剪切应力-应变关系及屈服点的剪切应力吻合良好,但是由于纤维和PEEK基体的浸润性较差,导致CF/PEEK复合材料内部存在孔隙缺陷,影响了CF/PEEK复合材料的初始剪切弹性行为,导致加载初始阶段存在偏差。Abstract: Carbon fiber reinforced polyether ether ketone (CF/PEEK) is a high-performance thermoplastic composite with broad application in aerospace. PEEK has a non-linear behavior related to temperature and strain rate, which makes CF/PEEK have similar mechanical behavior in plane shear direction. In this paper, shear experiments were carried out on CF/PEEK specimens at different temperatures and strain rates. The stress-strain curve was divided into linear and non-linear parts. It is found that temperature and strain rate have a greater influence on the yield stress of CF/PEEK. With the increase of temperature from 20℃ to 130℃, the yield stress decreases by about 66%, and the rate of decrease is fast and then slow. With the increase of strain rate from 10−5 s−1 to 0.1 s−1, the yield stress increases uniformly by about 35%. This phenomenon is fitted into an empirical formula of back stress, and the yield function of the classic elastoplastic constitutive model of thermoplastic composites is modified, which is applied in VUMAT to analysis the shear behavior of CF/PEEK. Compared with the experimental results, it is found that the yield point and the nonlinear stage are in good agreement. However, due to the poor infiltration of fibers and PEEK matrix, CF/PEEK composites have porosity defects inside, which affectes the initial elastic behavior of CF/PEEK composites and resultes in the deviation in the initial loading stage.
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Key words:
- CF/PEEK /
- non-linear behavior /
- strengthening behavior /
- temperature /
- strain rate
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表 1 碳纤维增强聚醚醚酮(CF/PEEK)复合材料力学性能
Table 1. Properties of carbon fiber reinforced polyether ether ketone (CF/PEEK) composite
Property Value Longitudinal modulus E1/GPa 130.00 Transverse moduli E2, E3/GPa 7.86 Transverse shear modulus G23/GPa 3.63 Axial shear moduli G12, G13/GPa 5.86 Poisson’s ratio in 23 direction ν23 0.51 Poisson’s ratios in 12 and 13 directions ν12, ν13 0.28 -
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