HEAT – High resolution detection of temperature distribution at cracktips of Amorphous Thermoplastics

温度的影响在聚合物和塑料的特性中起着重要的作用。机械加载过程中的本征加热尚未考虑。知道精确的热行为下加载能够得出结论的分子过程和制定相关的断裂动力学。认为裂纹扩展受软化过程的抑制或受分解的支持是合理的。为此，一方面，最大温升是非常重要的，另一方面，热量的时间和空间分布起着重要的作用。现在，这两者都可以用最先进的热成像设备进行测量，并通过分子动力学结构模拟进行预测。断裂过程中的能量释放一直是人们关注的焦点.然而，到目前为止还不可能令人满意地确定.裂纹尖端的微观软化甚至熔化过程是现实的情况。它们对塑料断裂性能和损伤容限的影响是零件设计中尚未考虑的。韧性、应变率和裂纹扩展的关系必须完全修正，材料模型也需要更新。在本项目中，将讨论这一主题，并提出新的方法与时间分辨率的测量和模拟工具。时间分辨率，可以解决和相关的断裂过程和相应的影响和机制是需要精确的温度测定沿着一个不断增长的裂纹前沿。因此，在较低的μm范围内的空间分辨率是必要的，以可视化弹性，塑性和开放区域以及不同的能量释放断裂特征。有了新型的热成像摄像机，这是可能的。同时将进行数值研究，这一方面将揭示分子水平上的机制，例如裂纹尖端加热或声发射。另一方面，通过利用成熟的有限元方法，将模拟真实的尺寸试样，同时考虑到实验结果以及纳米尺度模拟，从而将热和声学效应集成到损伤模型中.本项目所获得的知识可以从根本上重新思考以前的断裂模型，从而改进对塑料件损伤的解释和预测。

The influence of temperature plays an important role in thecharacterization of polymers and plastics. The intrinsic heating duringmechanical loading has not been considered yet. Knowing the precisethermal behaviour under loading enables to draw conclusions on themolecular processes and to formulate dependent fracture dynamics. Itis not unreasonable to believe that crack growth is inhibited bysoftening processes or supported by decomposition. For this, on onehand, the maximum temperature rise is of great importance and onthe other hand the temporal and spatial distribution of the heat plays asignificant role. Both can now be measured with state-of-the-artthermal imaging equipment and predicted with molecular dynamicstructural simulation. Energy release during fracture has been ofmuch interest in the past. However it was so far impossible todetermine satisfactorily. Microscopic softening or even meltingprocesses at the crack tip are realistic scenarios. They wouldinfluence the fracture properties and damage tolerance of plastics in away that has not been considered yet during part design. The relationof toughness, strain rate and crack growth would have to be revisitedcompletely and the material models would need to be updated. In thisproject this topic will be addressed and new approaches with temporalultrahigh resolution measurement and simulation tools are suggested.A temporal resolution that can resolve and relate the fracture processand the corresponding effects and mechanisms is needed for precisetemperature determination along a growing crack front. Therefore aspatial resolution in the lower μm range is necessary that visualizeselastic, plastic and open areas as well as different energy releasingfracture characteristics. With novel thermal imaging cameras this isnow possible. Simultaneously numerical investigations will beperformed, which on the one hand will reveal the mechanisms on the molecular level that are responsible for e.g. crack tip heating or acoustic emission. On the other hand by utilizing the well-establishedfinite element method real sized specimens will be simulated takinginto account experimental results as well as the nanoscalesimulations and thereby integrating thermal and acoustic effects intothe damage model. The knowledge acquired in this project can leadto a fundamental rethinking of previous fracture models and thusimproves the interpretation and prediction of damage of plastic parts.