The material described in this paper is a combination of long-fiber and textile reinforced thermoplastics processed by an innovative technique in one step. In order to evaluate the sandwich systern an automotive component has been selected. The goal is to offer a cost effective material with increased and load oriented mechanical properties by combining the advantages of a commingled woven fabric with long fiber reinforced thermoplastics (LFT). Beside describing the development of a suitable process technique this paper describes interactions between the TWINTEX facings and the core material during the forming process. The results show the importance of the determination of critical shear stresses depending on the materials used and the processing temperature. The glass fiber content dramatically influences the viscosity and flow behavior and with that the transferred shear stresses. lf a clamping frame is necessary the applied membrane tension has to be added to the membrane tension transferred by the flowing core material during direct forming. These results led to a new mold technology for the direct forming of therrnoplastic sandwich components. While forming geometrically high maintenance regions of a component the area wetted by the core material has to be limited. This can be realized in a leveled hydraulic press by advancing mold segments which limit the wetted sections and guarantee a forming of the sandwich structure free from penetration. The mold for the direct forming of the hemisphere in the middle of the plate was equipped with an advancing mold segment with an Hg value of approx. 1,5. As expected a direct forming of the component free from penetration could be realized. The results were successfully transferred to the geometry of a demonstrator part - the foot support of the MCC Smart city car.
Interactions of long-fiber reinforced core material with woven fabric reinforced facings during direct-forming of a thermoplastic sandwich-structure
Wechselwirkungen zwischen langfaserverstärktem Kernwerkstoff und gewebeverstärktem Obermaterial während des Direktumformens eines thermoplastichen Sandwichbauteils
2002
5 Seiten, 13 Bilder, 3 Quellen
Conference paper
English
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