Electrically-heated moulds of CRP composite materials for Automotive application. Prof. Dr. Herbert Funke

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1 Electrically-heated moulds of CRP composite materials for Automotive application

2 High temperatures in process increase efficiency in production mandatory for a lot of processes Efficiency increases if heating and cooling rates are very fast only the product itself is being heated areas of heating can be designed individually

3 The moulding-system FIBRETEMP: produces temperature just at the surface integrates structure and heating element Moulds can be heated up very fast can be manufactured at considerable costs are dimensionally stable (thermal expansion close to zero)

4 The way FIBRETEMP works: Carbonfibres are mould structure and heating element as well C-fibres are conductive only longitudinal the laminate works similar to a heating panel heating rate can be designed by structuring the layers

5 Fibre reinforced plastics enable the design of customized material The moulding-system FIBRETEMP enables the design of customized heating elements The special electrical characteristics in combination with mechanical properties of CRP are being used: longitudinal electric conductivity of Carbonfibres thermal expansion close to zero

6 Electrically heated plastic moulds (as known so far) The casted heating elements are designed like meanders Electrical resistance conductors with different electrical potential are separated by insulating material Electrical insulation is most of the times also (unwanted) thermal isolation High percentage of isolation/insulation increases the problem of deforming

7 Use of conventional C-fibre tissue Integral CRP Heating: Design of the mould can be a sandwich construction The top layer is the structure of the mould and also the electrical heating element Panel heating with low heat capacity and maximal heating surface very short ways of heat flow

8 electric parameters: FIBRETEMP-moulds have low electric resistance R i << 1 U 0 42 V (low voltage) high current (up to more than 400 A) design at about 500 W/m² ensure sufficient heating rates for most applications precise adjusting of temperature by electronic regulation

9 Freedom of individual design: heating elements can be designed individually by design of the layers individual geometric design of heating elements individual crossing and doubling of independent heating elements

10 Example of dimensioning: rectangular plate: length: mm / width: 400 mm 1. Layer: 400 g / m² C-fibre tissue; fibres: T300 ; 12 tex ; 2,5 fibres / cm electrical resistance of a single fibre 1 m lenght: 35 over a width of 400 mm 100 fibres are parallel

11 Example of dimensioning: rectangular plate: length: mm / width: 400 mm Electrical resistance of the first layer: R el, 1. layer = 0,35 (35 / 100) an additional layer divides the electrical resistance: R el, 2 layers in sum = 0,175

12 Example of dimensioning: rectangular plate: length: mm / width: 400 mm example: Heating at 10 V: R rectangular plate = 0,175 I = U / R = 57,1 A P = U I = 571 W P / A = 571 W / 0,4 m² = W/m²

13 Examples of Application Interior panels for a wide-bodied aircraft GFP sandwich elements are produced with prepregs in heated CFP-moulds Size of the moulds up to 18 m² a mould temperature of 100 C can be reached with a heating power of only 2 kw

14 FIBRETEMP in rotorblade manufacturing: fast heating rates Temperatures of the mould up to 150 C Easy and precise adjusting of temperature different heating circuts Little heating power required ( 500 W / m²) fast cooling down caused by low heating capacity of the mould itself efficient manufacturing of moulds

15 Examples of Application Structural components for special vehicles GFP sandwich elements are produced with prepregs in heated CFP-moulds Different geometries with different complexity Different heating zones can be realized.

16 additional applications: Thermoforming manufacturing thermoplasics temperatures up to 230 C very fast heating-rates (> 100 K / min possible) very precise adjusting of temperature consistant distribution of temperature all over the surface of the mould

17 Summary: The integrated CRP mould heating works macroscopically as panel heating with consistant distribution of temperature low heat capacity in the mould ensures : high heating-up rates The requirement of low heating power Short cool-down periods Moulds are dimensionally stable: Nearly no thermal expansion No shape distortion Cost-effective construction of moulds The heating power can easily be adjusted Easy customized design of heating elements

18 is awarded: JEC-Award 2008 for processing categorie AVK-Innovation-Award University-Award 2008

19 FIBRETEMP is a common development of: yachtwerft meyer