温度与应变率对聚羟基脂肪酸酯弹塑性力学行为的影响

Influence of temperature and strain rate on elastoplastic mechanical behavior of polyhydroxyalkanoates

为探究温度和应变率对聚羟基脂肪酸酯(PHA)的弹塑性力学行为的影响,首先对2种具有代表性的PHA(牌号分别为EM10080和EM20010)在4种不同的加载速率和2种不同温度下进行准静态单轴拉伸测试研究。测试结果表明2种牌号的PHA的力学性能(杨氏模量、屈服应力)均随温度升高而降低,而随应变率的增加而升高;并且由于EM20010的玻璃态转化温度为55.96℃,因而在22℃时表现出玻璃态的线弹性力学行为,而在62℃表现出橡胶态的弹塑性力学行为;此外,拉伸后样件表面都出现了平行于拉伸方向的微观裂纹,使得材料表面呈现出类似于被“撕裂”的形貌,E10080的撕裂孔呈梭形,而EM20010的撕裂孔呈条状。然后,依据试验数据,采用Johnson-Cook本构模型对EM10080的温度和应变率相关应力应变响应进行了模拟;并分别采用线弹性本构模型和传统弹塑性本构模型对EM20010在室温(22℃)和高温(62℃)下的应力应变响应进行了模拟。

In order to investigate the mechanical properties of polyhydroxyalkanoates and develop a convenient and ac⁃curate constitutive model,two representative commercial polyhydroxyalkanoates(EM10080 and EM20010,respectively)were subjected to quasi-static uniaxial tensile tests at four different loading rates and two different temperatures.The test results show that the mechanical properties including Young’s modulus and yield stress both increase with the rise of strain rate and decrease of temperature for both EM10080 and EM20010.Besides,EM20010 exhibits linear elastic be⁃havior of glassy state at 22℃while elastoplastic behavior of rubber-like state at 62℃since its glass transition tempera⁃ture is 55.96℃.Moreover,there are a number of ruptured cracks along the tensile direction on the surface of the stretched sample,and the cracks are fusiform for EM10080 but bar-shape for EM20010.Furthermore,based on the ex⁃perimental data,the Johnson-Cook constitutive model parameters were calibrated for EM10080.The linear elastic and the traditional elastoplastic constitutive models are calibrated to simulate stress-strain response for EM20010 at 22℃and 62℃,respectively.