JEC COMPOSITES MAGAZINE - Issue #65 - May/June 2011 - 62

thermoplastic
chain is the forming process. The shaping cycle time depends on the thermal conductivity and capacity of the material as well as the wall thickness of the resulting parts. The thermoforming cycle time for a part with a polyamid 6.6 matrix and a 2-mm wall thickness is approximately 70 seconds [7]. The heating and cooling time before part unloading increases in proportion to the square of the maximum wall thickness, so it is essential to minimize the wall thickness. This shows a special benefit of using tapelaid tailored FRP blanks. Due to the use of non-crimped continuous fibres, the fibre orientation of every layer within the tailored blank can be set load-dependent. Thus, a higher specific strength and therefore a minimum wall thickness can be reached. This reduces the material consumption and cycle time significantly. Pre-shaped customised plates require a lower degree of forming and therefore less powerful thermoforming stations. Furthermore, this enables a higher structure complexity due to the reduced forming radii within the subsequent thermoforming processes.
Fig. 4: Potential production paths

Flexible production strategy
The synergetic process characteristics resulting from the combination of tape laying and thermoforming in an integrated process chain, coupled with the weldability of thermoplastic FRPs, allow extremely flexible production paths and therefore a broad product portfolio (Fig. 4). In addition to its benefits in large-scale production, this method also offers huge opportunities in mid-scale and prototype production when using the diaphragm method as the forming process. Plaster moulds can also be used in the diaphragm process due to its comparatively low forming pressure of approximately 10 bars. Thus, operable prototypes can be produced in a flexible and efficient way using a procedure suitable for mass production.

jec composites magazine / No65 May - June 2011

Conclusion

Thermoplastic FRPs offer high potential to meet the increasing demands of modern automotive production. Due to the very high specific strength of continuous fibrereinforced thermoplastic composites, significant weight savings can be achieved,

offering huge opportunities to reduce CO2 emissions and energy demand (electric mobility). The good recyclability of thermoplastic FRPs translates into positive life cycle assessments. Due to the superior damping and force absorption behaviour of thermoplastic matrices, both the driving comfort and security of modern cars can be improved. Such high-performance lightweight structures can be produced with short cycle times, taking advantage of the insitu consolidation potential of thermoplastic FRPs and the synergies resulting from the combination of laser-assisted tape laying with the thermoforming process. In reaction to growing industrial interest, the Fraunhofer IPT created an independent department devoted to fibre-reinforced plastics and laser system technology in January 2010. This department specialises in the development of automation technology for the production of FRPs. It serves the industry by conducting technology and economic research, designing, assembling, certifying and on-site commissioning of customised production systems based on tape laying and thermoforming. The Fraunhofer IPT has the expertise and facilities needed to develop and implement process chains for the automated mid- and large-scale production of “green”, highperformance thermoplastic FRP structures. n
More information: www.ipt.fraunhofer.de E-mail: Joffrey.stimpfl@ipt.fraunhofer.de

References: [1] Grant C., Martin J.: Automated Processing Technology For Composites: Current Status and Visions For The Future. In: Proceedings of the 48th International SAMPE Symposium and Exhibition, Long Beach, CA, USA, 11-15 May 2003, S. 888-895 [2] Sehanobish K.: A Vison of Carbon Fibre Composites (CFC) in Automotive, Dow Chemical Company, www.speautomotive.com, 2009 [3] Zöllner O.: Grundlagen zum Schwindungsverhalten von thermoplastischen Kunststoffen, Bayer AG, 2008 [4] Schürmann H.: Konstruieren mit FaserKunststoff-Verbunden, Springer Verlag, 2007 [5] Burkart A.: Feasibility of continuous-fiber reinforced thermoplastic tailored blanks for automotive applications, SPE Automotive Composites Conference & Exposition, 2005 [6] Neitzel M., Mitschang, P.: Handbuch Verbundwerkstoffe - Werkstoffe, Verarbeitung, Anwendung. Carl Hanser Verlag München, 2004. ISBN 978-3-44622041-6 [7] Neitzel M., Breuer U.: Die Verarbeitungstechnik der FaserKunststoff-Verbunde Carl Hanser Verlag München Wien, 1997

http://www.speautomotive.com http://www.ipt.fraunhofer.de

JEC COMPOSITES MAGAZINE - Issue #65 - May/June 2011

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #65 - May/June 2011