Experiment and fractional derivative rheological modeling of the shear creep of HFRP overlap joints under dry and moist environments
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摘要: 搭接是纖維增強復合材料(FRP)的重要連接方式,長期性能是該技術實際工程應用的關鍵.對不同恒定應力和濕度狀態下混雜FRP (HFRP)雙搭接接頭的剪切蠕變性能進行了試驗研究.試驗觀測到了明顯的蠕變變形,測定了蠕變與恒定應力及濕度的關系.進一步采用分數階導數流變模型對試件的蠕變進行模擬.根據模型所包含的Mittag-Leffler函數的性質采用了改進的Powell優化算法,并確定了合理的初值,結合試驗曲線擬合得到模型各參數值.根據搭接接頭蠕變的特點,在經典分數階流變模型中引入了表征應力水平對搭接接頭非線性蠕變特性影響的函數,提出了一種改進的分數階蠕變柔量計算公式.研究結果表明,該流變模型能夠采用簡單的表達形式和較少的參數對試件的非線性蠕變行為進行擬合,在30%~70%恒定應力范圍內準確模擬了雙剪搭接接頭的蠕變曲線.Abstract: The long-term performance of overlap adhesion, one of the major joint technologies of FRP, is key to its practical engineering application. Experiments on the creep behaviors of the double lap joint of a hybrid FRP (HFRP) were conducted. Obvious creeps were observed and measured under various environments reflecting different levels of shear stress and humidity. Then, a fractional derivative rheological model was proposed to characterize the creep deformation of the overlap joints. By applying the Mittag-Leffler function to the proposed model, an improved Powell optimization algorithm with an initial-value calculation method was utilized to determine the values of the fitting parameters on the basis of the experimental data obtained. By introducing stress influence functions to the conventional fractional calculus, a modified formula of fractional creep compliance was considered to reflect the influence of stress level on the creep property of the overlap joint. Results indicate that the model is capable of predicting the creep behavior of overlap joints up to a sustained stress level of 30%-70% of the shear strength with relative simple mathematical expressions and only a few fitting parameters.
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Key words:
- HFRP /
- overlap joint /
- shear creep /
- fractional derivative rheological model
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參考文獻
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