Development and analysis of a material model based on the reptation theory for the description of the strain behaviour of PET at high strain rates

基于蠕动理论的材料模型的开发和分析，用于描述 PET 在高应变率下的应变行为

• 批准号: 328107189
• 负责人: Professor Dr.-Ing. Christian Hopmann
• 金额: --
• 依托单位: Institut für Kunststoffverarbeitung (IKV) in Industrie und Handwerk an der RWTH Aachen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/328107189?language=en
• 关键词: Development; analysis; material; model; based

The two-stage stretch blow moulding process is established as a method for producing high-quality plastic hollow bodies with excellent mechanical and optical properties. The stretching of the material during the process leads to a strong orientation of the molecular chains and to a formation of lamella like structures. These structures lead to a sharp increase in the strength of the material. The prediction of the material behaviour helps in the interpretation of the process and in the increase of the material efficiency in the production of hollow bodies or films. For the prediction of the material behaviour, different material models are used. Material models are currently described through spring-damper approaches and are calibrated through stress-strain curves. These models can predict the deformation within the calibrated range well, but are less accurate outside this range. The aim of this research project is the development and analysis of a material model, which depicts the stress strain behaviour of Polyethylenterephthalat (PET) based on the reptation theory. For this purpose, the equation set of the reptation theory for the description of the resulting stress in polymer melts is implemented and calibrated with the material data for amorphous (A) and semi-crystalline (C) PET determined. The first step of the project is the development of the material model. For this purpose, the equation system of the reptation theory for the description of plastic melts is fit to describe the behaviour of PET. The performance of the model is examined under different conditions for the specified PET types. The validation of the model is carried out by comparing the calculated stress strain curves for different temperatures with experiments. Furthermore, the model is applied in simulations of membrane-inflation rheometer (MIR) and the stretch blow moulding process to analyse the models accuracy by the comparison with experiments. A comparison between practical and simulated measurement of the MIR allows the analysis of the strain behaviour in small time steps during the deformation process. Therewith, the accuracy, but also weaknesses, of the model can be identified. Finally, the material model is embedded in a simulation of the two-stage stretch blow moulding process. The validation is realised through experiments and compared to an existing hyper elastic material model for PET. The complex geometry of the preforms and the inhomogeneous temperature distribution in the material make high demands on the accuracy of the model. With the acquired knowledge of the material behaviour of PET and the analysed quality of the model, the material and energy efficiency is addressed.

两阶段拉伸吹塑工艺是一种生产具有优异机械和光学性能的高质量塑料空心体的方法。在此过程中材料的拉伸导致分子链的强烈取向并形成片状结构。这些结构导致材料的强度急剧增加。材料行为的预测有助于解释过程并提高中空体或薄膜生产中的材料效率。为了预测材料行为，使用了不同的材料模型。目前，材料模型通过弹簧阻尼器方法进行描述，并通过应力应变曲线进行校准。这些模型可以很好地预测校准范围内的变形，但在该范围之外则不太准确。该研究项目的目的是开发和分析材料模型，该模型基于蠕动理论描述聚对苯二甲酸乙二醇酯 (PET) 的应力应变行为。为此，采用了描述聚合物熔体中产生的应力的蠕动理论方程组，并使用确定的非晶态 (A) 和半晶态 (C) PET 的材料数据进行了校准。该项目的第一步是材料模型的开发。为此，描述塑料熔体的蠕动理论方程组适合描述 PET 的行为。针对指定 PET 类型，在不同条件下检查模型的性能。通过将不同温度下计算的应力应变曲线与实验进行比较来验证模型。此外，将该模型应用于吹膜流变仪（MIR）和拉伸吹塑成型过程的模拟，通过与实验的比较来分析模型的准确性。通过比较 MIR 的实际测量和模拟测量，可以分析变形过程中小时间步长的应变行为。由此，可以识别模型的准确性，但也可以识别其弱点。最后，将材料模型嵌入到两阶段拉伸吹塑成型过程的模拟中。该验证是通过实验实现的，并与现有的 PET 超弹性材料模型进行比较。预成型件复杂的几何形状和材料中不均匀的温度分布对模型的精度提出了很高的要求。凭借对 PET 材料行为的了解以及对模型质量的分析，材料和能源效率得到了解决。