Multi-Scale Modeling of Crystallization and Fracture in Rubbery Polymers

橡胶聚合物是各种先进工程应用的组成部分。典型的例子包括轮胎、风管、涡轮增压器软管、汽车底盘悬架部件、飞机发动机的耐热和耐燃料密封件、石油和天然气行业运输用的柔性管道、土木工程应用中的弹性桥梁轴承。这些高分子材料表现出非常复杂的热力学行为。它们除了在大变形时具有高度的非线性弹性外，还具有复杂的非弹性特征，如粘弹塑性现象和类损伤响应。此外，弹性体的非晶态网络有结晶的倾向，这取决于热机械加载条件。这种温度和应变诱导的结晶可以极大地改变预期的产物响应。晶化对断裂韧性也有重要影响。本研究项目的目标是对这些现象进行建模，这对于橡胶聚合物失效机制的预测分析至关重要。近年来，橡胶聚合物粘弹性响应的高预测多尺度模型被开发出来，直接将复杂的宏观材料响应归结于聚合物网络的微观力学行为。先进的配方是所谓的橡胶弹性、粘弹性和mullins型损伤的微球模型，它们将聚合物链取向空间的非仿射链接解释为基于统计的单链机制的微观描述。该研究项目将微球模型扩展到非等温条件下橡胶聚合物应变诱导结晶和断裂的预测模拟。它将结合并推进三个方面：(i)橡胶聚合物中速率和温度相关的应变诱导结晶的多尺度建模，（ii）将其扩展到热粘弹性本构框架内的时间相关粘性效应，以及（iii）将其与断裂过程中裂纹扩展的可靠且计算效率高的概念相结合。该项目旨在向橡胶类材料的结晶和失效机制的可靠模拟迈出重要一步。

Rubbery polymers are integral elements of various advanced engineering applications. Typical examples include tires, air ducts, turbocharger hoses, chassis suspension components in automobiles, heat and fuel-resistant seals in aircraft engines, flexible pipes for transport in oil and gas industry, elastomeric bridge bearings in civil engineering applications. These polymeric materials exhibit a very complex thermo-mechanical behavior. Besides their highly non-linear elasticity at large deformations, complicated inelastic features such as visco-elastic-plastic phenomena and damage-like response occur. Furthermore, the amorphous network of elastomers has a tendency to crystallize depending on the thermo-mechanical loading conditions. This temperature- and strain-induced crystallization can drastically alter the expected product response. The crystallization also has a critical influence on the fracture toughness. Goal of this reserach project is the modeling of these phenomena, which is of utmost importance with regard to a predictive analysis of failure mechanisms in rubbery polymers. In recent years, highly predictive multi-scale models have been developed for the visco-elastic response of rubbery polymers, which directly root the complex macroscopic material response in the micro-mechanical behavior of the polymer network. Advanced formulations are the so-called micro-sphere models of rubber elasticity, visco-elasticity and Mullins-type damage, which account for a non-affine link of a polymer chain orientation space to statistically-based micro-descriptions of single chain mechanisms. This research project will extend the micro-sphere models towards predictive simulations of strain-induced crystallization and fracture in rubbery polymers under non-isothermal conditions. It will combine and advance three aspects: (i) the multi-scale modeling of rate- and temperature-dependent strain-induced crystallization in rubbery polymers, (ii) its extension to time-dependent viscous effects within a thermo-visco-elastic constitutive framework and (iii) their combination with reliable and computationally efficient concepts for crack propagation during fracture. The project intends to deliver a major step towards a reliable simulation of crystallization and failure mechanisms in rubberlike materials.