R24 project, producing the composites

Renault R24 Project: Once the moulds and templates have been produced, the production of the chassis proper begins in the operating theatre like-atmosphere of the composites department.

The right cut
An F1 chassis is not simply composed of one type of material: up to five different types go into producing the finished article, including carbon fibre, resins, and aluminium honeycomb. "The first step in cutting the carbon fibre is to transfer the digitised files of each part to the Lectra cutting machines," explains Composites Manager Colin Watts.

"Once this has happened, the software then collects together all the parts to be produced from a particular material, and organises them as efficiently as possible. One thing we can never change, though, is the orientation of material when it is cut: the fibres must run in a specific direction according to the forces the part is subjected to."

The collection of parts is called a 'marker', and once this is ready, the machine can begin cutting. "For the upper part of the chassis, we cut up to 500 different shapes which must then be laid up in the mould," explains Colin. Cutting all the markers for this part of the chassis takes between two and three hours.

Skins and sandwiches
The chassis itself is composed of three layer: the outer skin, the 'core' and the inner skin, in what is termed a 'sandwich' structure. "The outer skin comprises between 150 and 200 'plies', or cut shapes of carbon fibre," explains Colin. "We assemble the mould, and then begin 'laying up' the plies according to the drawings from the design office, paying careful attention to the orientation of these pieces. We apply different types of carbon fibre in layers, and the amounts of material vary according to the location on the chassis: certain key areas, such as the engine mounts or the roll hoop, require more material to cope with the forces involved."

During the preparation of the skins, the plies are cooked under pressure in the autoclaves in order to 'de-bulk' them, and squeeze the layers of material together. Once the skin is finished, it is then cured in the autoclave before the core and inner skins are added.

Stiff enough? Light enough?
In designing and producing the chassis, designers must constantly balance the conflicting demands of weight and stiffness. The thicker the 'sandwich', the stiffer the chassis, but it is also heavier; a thinner core brings advantages in terms of weight, but will flex more. Controls, though, are strict: "For the sides of the chassis, we must homologate the structure with the FIA," continues Colin. "We produce a sample of the chassis construction, which is then sent away and tested with an impact equivalent to having the nose of another car hit the chassis." Once this construction has passed the strength test, it is then fixed for the season.

A ten-man job
During the winter, the composites department works night and day, literally, to produce the chassis. "We have ten dedicated chassis laminators on day- and night-shifts," explains Colin. "We have two upper moulds and two lower moulds in the clean room at any one time, and lay up two chassis simultaneously." Although the chassis may require the greatest manpower, it is actually an exception to how the composites department usually works.

"For almost all other components, a single technician will produce the entire part from start to finish," concludes Colin. "It is not the most efficient method, but our system is optimised for producing the best quality part. It improves consistency, and also gives the technicians a real pride in their work." It's the kind of attention to detail that makes the difference in Formula 1.

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