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.

建立了两阶段的拉伸吹塑过程，是一种生产具有出色机械和光学特性的高质量塑料空心体的方法。在过程中材料的拉伸导致分子链的强烈取向，并形成了薄片类似结构。这些结构导致材料强度急剧提高。材料行为的预测有助于解释过程中空心物体或膜生产中物质效率的提高。为了预测材料行为，使用了不同的材料模型。目前，通过弹簧压接方法来描述材料模型，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，但在此范围之外较少准确。该研究项目的目的是对材料模型的开发和分析，该模型描述了基于繁殖理论的多乙醇脑及苯甲酸酯（PET）的应力应变行为。为此，用无定形（a）和半晶（c）PET的材料数据来实现和校准，并校准了对聚合物熔体中产生应力的描述的方程集。该项目的第一步是材料模型的开发。为此，用于描述塑料融化的仓库理论的方程式系统适合描述PET的行为。该模型的性能在指定的宠物类型的不同条件下进行了检查。模型的验证是通过将不同温度的计算应力应变曲线与实验进行比较。此外，该模型应用于膜通气流变仪（MIR）和拉伸吹塑过程中，以通过与实验进行比较来分析模型的精度。对MIR的实际测量和模拟测量之间的比较允许在变形过程中以较小的时间步骤分析应变行为。因此，可以确定该模型的准确性，但也可以识别出弱点。最后，将材料模型嵌入到对两阶段拉伸吹塑过程的模拟中。验证是通过实验实现的，并将其与PET现有的超弹性材料模型进行了比较。材料中预形成的复杂几何形状和材料中的不均匀温度分布对模型的准确性提出了很高的要求。借助对PET的材料行为的知识以及模型的分析质量，解决了材料和能源效率。