JEC COMPOSITES MAGAZINE - Issue #39 - March/April 2008 - 47

Natural fibre More information The Institut für Verbundwerkstoffe GmbH (IVW) is a research institute located in Kaiserslautern, Germany. The institute focuses on the field of polymer-based composite materials, covering all aspects from material science, design and calculation to production technology. Component manufacturing and results In the scope of this work, vacuum press technology was used instead of the conventional press process commonly used for natural-fibre composites. Press plates were manufactured without additional conditioning in a plant at Wickert Maschinenbau GmbH. The prepregs were pressed at 20 bar in a mould preheated to 200°C. Due to the residual moisture content in the prepregs and the condensation products from the curing reaction, the cavity had to be ventilated briefly during the press cycle. The first step consisted in determining the pressing parameters under usual press conditions without vacuum. After several trials, a press time of 100 seconds was established. The consolidated plates were taken directly from the heated mould and cooled down at room temperature, without any deformation. When press time was reduced, bubbles were observed on the surface of the cured materials. Using the same parameters, several test plates were pressed in the vacuum chamber. It took just a few seconds to reach a pressure of approximately -1mbar, and the total press time of 100 seconds was maintained. These plates exhibited a better surface with more regular colour. In addition, the working conditions were notably improved, since the direct evacuation of the evaporating moisture reduced the noise and odour level during the pressing process. The process was further optimized though a systematic reduction of the total press time. In the end, a 50% reduction was achieved without impairing the mechanical properties of the composite. Several tests were carried out to characterize the mechanical properties of the components. Despite the low matrix content, all the natural-fibre-reinforced composites produced under all press conditions showed high mechanical properties, meeting the automotive industry’s requirements for interior parts. These good mechanical characteristics can be attributed to the very good distribution of the matrix particles within the prepreg and to the very good fibre/matrix adhesion. SEM analyses of the composites showed the regular appearance of fibre defibrillation in the fracture surface (Figure 3). Fig. 3: Defibrillation of the fibers in a fracture surface Fig. 4: Good wetting of fibre bundle by the matrix Additionally, no air gap was found in the boundary surface, indicating very good fibre-surface wet-out by the matrix (Figure 4). The material was developed primarily for the automotive Fig. 5: industry. In Door cooperation with panel lining system suppliers, (courtesy different parts were Polytec GmbH) manufactured in mass production moulds under standard conditions (Figure 5). The moulded components did not show any warpage or deformation after demoulding and cooling. Natural-fibre-reinforced composite materials are not limited to automotive applications, so the new fibre composite was also used to manufacture a variety of components such as executive cases, trays, and a sport seat (Figure 6). Fig. 6: Press-moulded sport seat Conclusion One of the procedure’s main advantages is that, unlike thermoplastic-matrix prepregs, no additional pre-heating step is required, giving a very short cycle time (under a minute). Due to the easy handling compared to alternative procedures, form pressing of natural-fibre-reinforced thermoset-matrix prepregs is a very promising method for manufacturing high-strength, high-rigidity structural components with minimum component weight. More information: www.ivw.uni-kl.de No39 March - April 2008 / JEC Composites Magazine 47

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JEC COMPOSITES MAGAZINE - Issue #39 - March/April 2008

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