In a collaboration with KraussMaffei, Henkel has developed a process for the manufacture of composite components using high-pressure RTM technology that creates a surface quality good enough for automobile exteriors.
Henkle’s partner network which includes carbon fiber manufacturer Zoltek and the sports car builder Roding Automobile have created a lightweight yet high-strength carbon roof segment of the 950 kg sports car, the superlight Roding Roadster R1 to showcase the process.
Composite materials based on carbon fibres combine lightness in weight with enormous strength, thus also offering outstanding characteristics in terms of safety and crash behavior. Good mechanical properties such as rigidity in the resin system employed are thus essential, particularly when it comes to absorbing the huge forces encountered in motor sport.
Until now, there have been certain limitations in the use of lightweight components as they are restricted in the degree to which they can meet the requirements of the automotive industry in respect of cycle times and level of automation. In particular, composites have been very rarely used for the external components of vehicles as the requisite post-treatment of the surface for subsequent painting has been too costly and time-consuming, based as it is on manual processes.
KraussMaffei together with a partner network has now succeeded in producing in a fully automated process composite components that exhibit a surface quality suitable for immediate painting. This has become possible thanks to the development of Loctite MAX 3: This new, three-component polyurethane-based matrix resin system from Henkel contains not only the resin and hardener but also a high-performance release agent aligned to a self-releasing polyurethane lacquer manufactured by Rühl Puromer GmbH.
Georg Käsmeier, Managing Director of Roding Automobile said;
The component quality achieved in this project with Loctite MAX 3 is outstanding. Given the clear trend toward painted carbon components in particular, we see enormous potential for this process being used in conjunction with RTM technology for duplicate industrial production.
The polyurethane-based matrix resin technology is characterised by significantly faster curing compared to the epoxy resins usually used for the resin transfer moulding process. Due to its low viscosity, the resin penetrates the fibre material more easily and with less alignment disruption, giving rise to shorter injection times and thus short cycle times in series production.
Henkel has also improved the temperature resistance of the PUR resin, bringing Loctite MAX 3 up to a level comparable with that of epoxy resins in relation to this particular property. This high temperature resistance means that the fibre-reinforced composites can be de-moulded quicker.
With the internal release agent ensuring easy detachment of the component from its mould, the resultant surface is of sufficiently high quality to allow immediate painting and bonding. While enabling manufacture of external and visible components with an outstanding surface quality, this also accelerates the production process, facilitating increased automation and thus mass production.