Published on Feb 28, 2024
Carbonfibre is a non isotrope material. That means that all fibres have to point the same direction as the forcelines through the material. If this is not the case, there will be an opposite effect. To be understandable, wood is also not isotrope, aluminium and copper are for sure.
Most commonly, carbon fibres are produced from the polymere PAN, so we will only consider this type of manufacturing. After an improved Sohio process which involves an amonoxidation reaction between propene and ammonia, the result is acrylonitrile, which transforms into polyacrylonitrile after polymerisation.In the beginning of the sixties, Colin Chapman, chief designer of Lotus, introduced the monocoque to formula one by placing thin plates around the bars of the monocoque. This new technology increased the stiffness of the chassis.
Later on in the seventies, aluminium was mostly used for these constructions, but when these structures porved not be be resistant enough for the wings' downforce, John Barnard examined and produced as a first the self supporting chassis from carbonfibre. The engineer fom McLaren he had it produced by the American company " Hercules Aerospace" because McLaren didn't have the materials and knowledge to do this. In 1981, the McLaren drivers proved the safety and advantages of the new way of construction. John Watson finished two times second and once first in that season. Andrea De Cesaris proved ste stiffnes of the monocoque, with the plenty of crashes he made in that season.
F1 teams use carbon fibres, a pre-impregnated epoxy resin and an aluminium honeycomb layer, which is sandwiched between two layers of carbon fibre.The chassis is usually the first part of the car to be built, due to the amount of time required. The main chassis usually comprises of about 8 parts (panels). The first stage of the manufacturing process is to build a solid (computercut) pattern, from which a mold for the panel is produced. The molds are constructed by laying a total of 10 layers of pre-impregnated (with resin) carbon fibre on top of each pattern to produce the mold. The production of the mold takes place in several stages, involving vacuum treatments, debulking and heating processes. The mold then has to be thoughroughly cleaned and prepared for use.
The next phase is the actual fabrication of a car part, made from sheets of pre-cut, pre-impregnated carbon fibre, which are carefully laid inside the molds. It is thereby vital orientate the carbon fibre sheets in pre determined directions in order to achieve the desired strength. A total of 5 layers of carbon fibre are laid, forming the outer skin of the chassis (to achieve a final, cured thickness of 1mm, a total of 3-4 layers of carbon fibre must be laid down).
The next stage of the process is to cure the carbon fibre in an autoclave. This exposes the carbon fibre to a number of temperature / pressure cycles according to the specific requirements of the materials and components being processed. During this treatment, the resin impregnated in the carbon fibre flows into the surrounding fibres and is activated, thereby curing the carbon fibre. Once the outer skin has been cured and cooled down, a honeyomb layer of aluminium is fixed onto the outer skin by a sheet of resin to ensure the materials stick stongly together.
The chassis panel then returns to the autoclave for curing. After having cooled down again, one more layer, consisting of a number of pre-impregnated carbon fibre sheet is placed on top the existing skin, and again treated in the autoclave for a final time.
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