Experimental investigation and modelling of strain- induced crystallisation in natural rubber in different ageing conditions

天然橡胶(NR)中的应变诱导结晶(SIC)被认为是其优异性能的主要来源，如自增强和高撕裂性能，特别是当天然橡胶被纳米粒子填料进一步增韧时。因此，天然橡胶常用于汽车轮胎、隔振器、管道和发动机悬置。这个基础项目不是关于零件或结构的检查、建模和模拟，而是关于材料特性的。由于碳化硅降低了裂纹扩展的速度，上述应用只是作为该项目的动力。跨学科的SICX项目有以下目标：(1)在不同尺度上进一步研究碳化硅的动力学；(2)开发基于物理的三维模型，用于碳化硅下天然橡胶的材料行为，该模型在各种热机械路径下的大应变下将是稳健的；(3)理解和模拟环境条件对问题(1)和(2)的影响。先进材料科学的最终目的是在正确识别的物理机制的基础上，在真实的操作条件下对技术材料进行建模。该项目是实现三维有限元软件应用的第一步。因此，未来可以对真实的部件和系统进行建模，以便预测它们在实际加载条件下的响应。环境条件通常会导致弹性体的降解。除了热老化和热氧化老化外，还有因暴露在溶剂和紫外线照射下的循环变形或老化而引起的疲劳。所有方面对实际应用都非常重要，但不是所有方面都可以在这个项目中探索。因此，SICX项目只专注于有限数量的环境条件及其与天然橡胶中碳化硅的相互作用；有以下三个目标：1)确定与碳化硅相关的物理机制，这些机制尚未得到充分研究，或在科学界仍存在部分争议。2)量化了最重要的环境条件对碳化硅的影响。3)收集基于物理的微观和宏观实验数据，适用于在实际操作条件下表现出碳化硅的弹性体的连续力学模拟。

Strain-induced crystallisation (SIC) in natural rubber (NR) is considered to be the main source of its outstanding properties such as self-reinforcement and high tear resistance, especially when NR is further stiffened by nanoparticle fillers. For this reason, NR is often used in vehicle tires, vibration isolators, pipes and engine mounts. This fundamental project is not about examining, modeling and simulation of parts or structures, but of material properties. As SIC reduces the speed of crack propagation, the applications mentioned above serve only as a motivator for the project. The interdisciplinary SICX project has the following targets: (1) further investigations of the kinetics of SIC on different scales; (2) development of a physically based three-dimensional model, for the material behaviour of NR under SIC, which would be robust at large strain for various thermomechanical paths; (3) understanding and modelling the impact of environmental conditions on issues (1) and (2). The ultimate purpose of advanced materials science is the modelling of technical materials under real operating conditions, based on correctly identified physical mechanisms. This project is the first step on the way to an application in a three-dimensional finite element software. Hence, real parts and systems can then be modelled in future in order to predict their response under realistic loading conditions. Environmental conditions commonly lead to a degradation of elastomers. Besides thermal and thermo- oxidative ageing, there is fatigue caused by cyclic deformations or ageing due to the exposure to solvents and ultraviolet irradiation. All aspects are of enormous importance for practical applications but not all can be explored in this project. Therefore, the SICX project is focussed only on a limited number of environmental conditions and their interactions with SIC of NR; with the following three objectives: 1) Identification of the physical mechanisms associated with SIC, which have not been fully examined yet or remain partly controversial in the scientific community. 2) Quantification of the impact of the most important environmental conditions on SIC. 3) Collection of physically-based micro- and macroscopic experimental data suitable for continuum mechanical modelling of the behaviour of elastomers exhibiting SIC in real operating conditions.