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Continuum mechanical representation of the process-dependent caloric and thermomechanical behaviour of semicrystalline polymers

半结晶聚合物过程相关的热量和热机械行为的连续力学表示

基本信息

批准号：
328407295
负责人：
Professor Dr.-Ing. Thomas Böhlke
金额：
--
依托单位：
Bereich Kontinuumsmechanik
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/328407295?language=en
关键词：
Continuum mechanical representation process dependent

项目摘要

Due to their versatility, the mechanical, physicochemical and thermodynamic understanding and the representation of semi-crystalline polymers are for many years in the centre of research projects. Semi-crystalline polymers exhibit spatially separated regions in which the molecules form amorphous and crystalline phases. In between, there is often an interphase. It usually possesses a higher glass transition temperature than the mobile amorphous phase and is therefore referred to as a rigid amorphous phase. The current research project deals with the phenomenological and micromechanical modelling of the process-dependent behaviour of semi-crystalline polymers under thermal and volumetric loads and has the following main objectives: 1) Modelling of crystallization and melting of a semi-crystalline model polymer as function of temperature and pressure on the basis of a consistent experimental database. To this end, the methods of phenomenological continuum thermomechanics with internal variables are applied. The constitutive model is formulated for three spatial dimensions and specialized to represent the volumetric behaviour. In order to understand the local mechanisms at the phase boundaries and to check or improve the assumptions made in the framework of the phenomenological model, such as the existence of three phases or the mathematical structure of the evolution equation for the degree of crystallization, a method of homogenisation will be developed that can describe the mesoscopic properties of the material on the basis of the microscopic behaviour of the individual phases. 2) Micro-mechanical modeling of melting and crystallization. The kinetics of the crystallization should be the basis of a simplified micro-structure model (based on rank-1 and rank-2-laminates with constitutively modelled interface) which allows a quantitative understanding of the crystallization, starting from a spatially resolved model with mobile phase boundaries. The two constitutive models to be developed provide first blocks are within a complex modeling strategy which goes beyond this project. Experimental data of a model polymer form an essential basis for the constitutive representation with respect to calorimetry and thermomechanics. For the model development and the identification of the influence of the mechanical and thermal loading histories on the crystallization and melting behavior, an appropriate model polymer is to investigate experimentally. As many material parameters as possible (for example, the mechanical and caloric material parameters of the amorphous and crystalline phases) are used for the phenomenological and micromechanical model. This is possible because both models exhibit similar physical properties.

由于半结晶聚合物的多功能性，机械、物理化学和热力学的理解和表征多年来一直是研究项目的中心。半结晶聚合物表现出空间分离的区域，其中分子形成非晶相和结晶相。在这两者之间，常常有一个相间期。它通常具有比流动非晶相更高的玻璃化转变温度，因此被称为刚性非晶相。目前的研究项目涉及半结晶聚合物在热和体积载荷下的过程相关行为的唯象和微机械建模，主要目标如下：1）基于一致的实验数据库，对半结晶模型聚合物的结晶和熔化作为温度和压力的函数进行建模。为此，应用了具有内变量的唯象连续介质热力学方法。本构模型是针对三个空间维度制定的，专门用于表示体积行为。为了了解相边界的局部机制，并检查或改进唯象模型框架中所做的假设，例如三相的存在或结晶度演化方程的数学结构，将开发一种均质化方法，该方法可以根据各个相的微观行为来描述材料的介观性质。 2）熔化和结晶的微观机械建模。结晶动力学应该是简化微观结构模型（基于具有本构建模界面的 1 级和 2 级层压板）的基础，该模型允许从具有流动相边界的空间解析模型开始定量了解结晶。要开发的两个本构模型提供了第一个块，它们位于超出本项目范围的复杂建模策略中。模型聚合物的实验数据构成了量热学和热力学本构表示的重要基础。为了模型开发和识别机械和热载荷历史对结晶和熔融行为的影响，需要通过实验研究合适的模型聚合物。现象学和微观力学模型使用尽可能多的材料参数（例如，非晶相和结晶相的机械和热量材料参数）。这是可能的，因为两种模型都表现出相似的物理特性。