Composite automation
Carbon fibre reinforced polymer (CFRP) parts make up the majority of a modern Formula One car by volume. The combination of light weight and high strength makes them ideal for car construction, but they do have their disadvantages. One of the most notable is the cost, in both time and money, of producing the complex parts used in a Formula One chassis. Even Formula One teams have finite budgets, so the latest developments in automated composite production are of increasing interest.
These advances have stemmed from the aerospace industry and, to a lesser extent, mainstream automotive production. These industries have invested heavily in automated composite systems in order to reduce the cost of series production parts. In Formula One, most parts are produced as one-offs or in very short production runs, so the benefits of automated production are not great. However, several manufacturers have indicated that they are investigating the potential of automated systems within Formula One and the broader motorsport industry. Whether they will see widespread adoption though remains to be seen, but it is pertinent to look briefly at the technologies available.
Resin transfer moulding (RTM) is the most common process currently used for larger scale production of composite parts. RTM uses a rigid two-sided mould set that forms both surfaces of a panel. The mould is typically constructed from aluminium or steel, but composite moulds are sometimes used, the two sides fitting together to produce a mould cavity. Once the mould is closed, the resin is introduced under pressure, filling the voids between the material tows.
This allows complex panels to be produced rapidly; however, the nature of the process results in a higher resin-to-fibre ratio than with traditionally manufactured pre-preg based parts. This has potential implications for the structural integrity of parts, meaning that components made using RTM may need to be designed with a greater volume of material to offset this weakness, impacting on overall weight. Producing the moulds can also be prohibitively expensive, especially where short production runs are involved.
Automated fibre placement is another area that has seen extensive advances and development of late. Instead of placing sheets of pre-preg material by hand, robotic arms places individual fibres automatically. The material is deposited by a specially controlled machine head that keeps the resin-impregnated fibres cold before laying and then heats them as they are laid, ensuring that they stick to the other fibres in the structure. After being laid, the machine compacts the fibres together using a roller system, removing the need for autoclaving. Because of the short production runs in Formula One, this technology has yet to catch on, but several companies involved in the sport are investigating its potential for producing parts that do not change during a season.
A similar process, automated filament winding, which works on the same basis but winds fibres around preformed mandrels, does see extensive use in the production of components for Formula One. For example, CFRP pressure vessels used for accumulators are made using this production technique, which allows for the relatively rapid manufacture of high burst strength, low weigh pressure vessels.
Written by Lawrence Butcher