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Multi-Scale Modelling of Thermoplastic Fibre Reinforced Composites during Thermoforming

热成型过程中热塑性纤维增强复合材料的多尺度建模

基本信息

批准号：
314569760
负责人：
Professor Dr.-Ing. Thomas Gries
金额：
--
依托单位：
Institut für Textiltechnik (ITA)
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 2021-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/314569760?language=en
关键词：
Multi Scale Modelling Thermoplastic Fibre

项目摘要

Standard fibre-reinforced polymers contain a thermoset polymer matrix, where the polymer is cured irreversibly by a chemical reaction. Novel thermoplastic composites excel in the ability to undergo repeated heating, forming, and cooling. Further advantages include shorter part cycle times, ease of storage and handling, increased toughness, and recyclability. For these reasons the application of thermoplastic composites becomes more and more popular. The final part producer heats up the blank above the melting temperature and forms it into the final part shape.However, process stability is a major problem. Residual stresses due to thermal gradients and coefficient of thermal expansion mismatches between fibre and matrix might lead to shape distortions of the final part. To counteract this effect, process parameters such as heating and cooling rates, tool shape, and part positioning must be carefully determined. This is typically done by trial and error, partly vitiating potential time and cost advantages. To improve the situation, computational models of the thermoforming process are needed which can predict residual stresses and distortions of the composite parts. Existing models meet these requirements only partly. The build-up of residual stresses must be considered at multiple scales, at the fibre level as well as at the tow level, whereas the tow includes thousands of fibres. The entire process temperature range of the polymer must be considered, from room temperature to above the melting temperature. Finally, the melting and solidifying of the polymer in the presence of fibres must be fully characterised and considered.The project will result in a scale-bridging thermoforming simulation with three major innova-tions. First of all, a matrix constitutive model for the entire temperature range of thermoforming shall be developed. It will find application at the fibre and at the tow level. Secondly, a tow model will be created for both solid and liquid matrix phases. At last, the models for fibre and tow will be fully characterised experimentally over the entire temperature range. It is expected that the final result of the project is a multi-scale simulation tool for thermoforming with a new level of fidelity.

标准的纤维增强聚合物含有热固性聚合物基质，其中聚合物通过化学反应不可逆地固化。新型热塑性复合材料在经受反复加热、成型和冷却的能力方面表现出色。进一步的优点包括更短的部件周期时间、易于储存和处理、增加的韧性和可回收性。由于这些原因，热塑性复合材料的应用变得越来越普遍。最终零件生产商将坯料加热到熔化温度以上并将其成型为最终零件形状。然而，工艺稳定性是一个主要问题。由于纤维和基体之间的热梯度和热膨胀系数不匹配而产生的残余应力可能导致最终部件的形状变形。为了抵消这种影响，必须仔细确定工艺参数，如加热和冷却速率，工具形状和零件定位。这通常是通过试错来完成的，部分地损害了潜在的时间和成本优势。为了改善这种情况，需要热成形过程的计算模型，它可以预测复合材料零件的残余应力和变形。现有的模型只能部分满足这些要求。残余应力的积累必须在多个尺度上考虑，在纤维水平以及在丝束水平，而丝束包括数千根纤维。必须考虑聚合物的整个工艺温度范围，从室温到高于熔融温度。最后，必须充分表征和考虑纤维存在下聚合物的熔融和固化。该项目将产生具有三个主要创新的尺度桥接热成型模拟。首先，应开发热成形的整个温度范围的基质本构模型。它将在纤维和丝束水平上得到应用。其次，将为固体和液体基质相创建丝束模型。最后，纤维和丝束的模型将在整个温度范围内进行充分的实验表征。预计该项目的最终成果是一个具有新的保真度水平的热成型多尺度模拟工具。