Investigations on the relationship between processing, microstructure and properties of one-step long-fibre reinforced polymer sandwich components

本项目的目的是研究采用不同的泡沫注射成型技术一步成型的长纤维增强聚合物夹层构件的加工、微观结构和性能之间的关系。具体而言，久负盛名的MuCell®技术(Trexel Inc.)代表了该领域最先进的技术，因此是本项目中的参考技术，将其与基于双螺杆挤出机内发泡剂的重量添加的新型LFT-D发泡技术进行了比较。热塑性泡沫注塑成型(TSG)的两种变种都产生了由一种材料(LFT-D)制成的整体生产的泡沫结构，具有致密的面片，因此代表了三明治结构。夹层的所有部分(面板和芯层泡沫)都是长纤维增强的，对于非增强材料，材料性能、泡沫结构和工艺参数之间的关系已经得到了深入的研究，而对于长纤维增强泡沫材料，这些关系至今还不清楚。这一差距将通过实施拟议的项目来弥合。为此，将分别使用和应用提供变温过程控制的模块化剪切刃口模具来调整芯板比。可改变的模具镶嵌提供了高度的灵活性，关于组件几何形状(翅片、珠子、螺丝凸台)以及其对发泡行为的影响的研究。在这方面，出现了实施的纤维如何影响发泡过程、如何根据工艺参数调整泡沫/面片比率以及纤维如何作为发泡和注射过程中的人工制品在复合材料内部取向的问题。此外，必须澄清的是，从非增强泡沫中已知的工艺、微结构和性能之间的相关性是否可以转移到长纤维增强泡沫中。这些发现将与最终的力学性能相关，从而与泡沫结构的材料模型相关。因此，在准静态或冲击载荷作用下的性能是主要关注的问题。在这一点上，将考虑两种工艺变体之间的差异，因为与MuCell®技术相比，LFT-D-路线允许在最终产品中使用更长的纤维。

The aim of the project is the investigation of the relationship between processing, microstructure and properties of long-fibre reinforced polymer sandwich components processed in one step by different foam injection molding technologies. In detail, the well-established MuCell®-technology (Trexel Inc.) representing the state-of-the-art in this field and being therefore the reference technology in this project is compared to the novel LFT-D-foaming technique based on a gravimetric addition of the foaming agent inside a twin crew extruder. Both variants of Thermoplastic foam injection moulding (TSG) result in an integrally produced foam structure made from one material (LFT-D), possessing dense face sheets and hence representing a sandwich structure. All parts of the sandwich (face sheets and core foam) are long-fibre reinforced.For non-reinforced materials, the correlation between material properties, foam structure and processing parameters have been thoroughly researched on, while for long-fibre reinforced foams, these correlations are unknown up today. This gap will be closed by carrying out the proposed project. For this purpose, a modular shearing edge mould offering a variothermic process control to adjust the core/face sheet ratio wil be used and applied for respectively. Changeable mould inlays offer high flexibility regarding the component geometry (fins, beads, screw bosses) as well as the investigation of its influence on the foaming behaviour. In this regard, the question arises how the implemented fibres may influence the foaming process, how the foam/face sheet ratio may adjusted depending on the process parameters and how the fibres may be oriented inside the composite as an artefact from the foaming and injection process. Furthermore, it has to be clarified whether the correlations between process, microstructure and properties known from non-reinforced foams may be transferred to long-fibre reinforced foams. These findings will be correlated with the outcoming mechanical properties and consequently with material models for foam structures. Hereby, the behaviour under near-service, i.e. quasistatic or impact, loads is major interest. In this regard the difference between the two processes variants will be considered as the LFT-D-route allows for longer fibres in the final product in comparison to the MuCell®-technology.