Process influence in the combined compaction and back-injection process for manufacturing of self-reinforced composites

在挤压过程中，可以生产高强度纤维或胶带。熔融变形和固态拉伸的结合导致了高度各向异性的性能，在取向方向上的强度和刚度是传统注塑样品的5到6倍。这些性能可用于生产自增强复合材料。纤维或胶带首先被加工成纺织品。随后，它们被堆叠成几层，并在热压实过程中固结成自增强复合材料系统。本研究项目的目的是调查必要的基础，以便能够评估复合材料生产过程中热压实和反注射工艺的影响。该工艺通过在一个工具中同时进行固结和反向注射成型工艺，可以生产自增强复合材料。在后注射区，堆积的纺织品仅通过聚合物熔体的注射压力进行固结。自增强材料的微观结构受熔体流入的影响很大，直接关系到材料的力学性能。通过这种温度敏感性，自增强复合材料可以分级，这意味着由于不同的工艺设置，实现局部不同的机械性能。这可以用于生产在规定区域具有不同刚度的部件，仅由不同的工艺控制引起，而材料的化学性质相同。因此，生产的单材料系统由固化纺织品和同一聚合物的注塑组件组成。这导致了优异的回收性能。在本研究项目中，在对自增强复合材料进行热分级和不进行热分级的情况下，研究了组合压实和注射成型工艺对材料微观结构、试件翘曲、熔体与复合材料之间的粘合、复合材料的机械性能以及流动路径上的局部压力和温度水平的影响。最后用描述模型对局部条件进行了总结。这是为了形成对工艺的理解和由这种制造工艺生产的部件的构造的基础。

In an extrusion process, high-strength fibers or tapes can be produced. A combination of melt deformation and solid state drawing results in highly anisotropic properties, with up to 5 or 6 times higher strength and stiffness, in direction of orientation, than the conventional injection-molded samples. These properties are used for the production of self-reinforced composites. The fibers or tapes are first processed into textiles. Subsequently they are stacked in several layers and are consolidated to a self-reinforced composite system in a hot compaction process. The aim of this research project is to investigate the necessary fundamentals in order to be able to assess the process influences during a combined hot compaction and back-injection process to produce composites. This process enables the production of self-reinforced composites by means of a simultaneous consolidation and back-injection molding process in one tool. In the back-injected areas the stacked textiles are consolidated by the injection pressure of the polymer melt only. The microstructure of the self-reinforced material, which is directly related to the mechanical properties, is highly influenced by the inflowing melt. By means of this temperature sensitivity, self-reinforced composites can be graded, which means the implementation of local different mechanical properties, due to different process settings. This can be used to produce components with different stiffness in defined areas, only caused by the different process control, while material is chemically identical. Thus, monomaterial systems are produced which consist of consolidated textiles and an injection molded component of the same polymer. This results in excellent recycling properties.Within this research project, the influence of the combined compaction and injection molding process on the microstructures of the material, the warpage of the specimen, the adhesion between the melt and the composite, the mechanical properties of the composite and the local pressure and temperature levels along the flowpath are investigated, with and without a thermal grading of the self-reinforced composites. The local conditions are finally summarized in a describing model. This is intended to form the base for the understanding of the process and the construction of components produced by this manufacturing process.