What Is A Monocoque?

What Is A Monocoque
What Is A Monocoque

The word monocoque is a French word and means a single cell. Monocoque is derived from the Greek words: “mono” for single and “coque” for cell. In Formula 1, monocoque refers to the “survival cell” that protects the Formula 1 car driver. The cell is made from carbon fibre reinforced composites and is virtually indestructible. The monocoque, despite being strong, is also amazingly light. This helps constructors keep the weight of the car as low as possible. A monocoque protects the driver when a Formula 1 car meets with an accident or crashes.

Formula 1 racing has always been a dangerous sport, particularly for drivers. Every Formula 1 driver knows that he is risking his limbs and life when he seats in a Formula 1 car. The risk goes with the speeds at which the cars race. A driver has very little reaction time to take action in an impending crash when travelling at 300 km/h or more. The reactions are mostly instinctive and sometimes dangerous. This risk makes keeping the driver safe in any conditions imperative and the FIA takes the matter seriously.

Before 1985, car safety was handled by each team and the FIA had very little role to play in driver safety. This led to many accidents, injuries and casualties bringing bad publicity to Formula 1. The FIA noticed that and made crash tests mandatory before allowing a car to compete in Formula 1. The constructors’ and Formula 1 research teams and engineers started working together on Formula 1 drivers’ safety. The use of monocoques in the construction of Formula 1 cars resulted from this work. The FIA mandates several tests on monocoques, that cover every aspect of safety in case of an impact.

What is an F1 monocoque?

With the improvement in engines and the speeds of Formula 1 cars, the incidents were also on the rise on race tracks. The risk to Formula 1 drivers, race officials as well as spectators were also increasing. Injuries and casualties also increased highlighting the risk to personnel involved with a Grand Prix. The FIA and constructors of Formula 1 cars decided to make cars as safe as possible for all concerned. The aim was to minimise risk to the drivers by limiting the damage caused by an impact and keeping the debris emanating from an incident to a minimum. This move was to greatly improve the safety of personnel involved with racing.

The Lotus team designer and boss Colin Chapman was the first man to use a monocoque in a Formula 1 car. Conventionally a tubular aluminium space frame was used in the construction of Formula 1 cars. Chapman used a riveted lightweight metal case instead of a tubular frame in the Lotus 25 in 1962. That was the first instance of the use of a monocoque in a Formula 1 car. The experiment was highly successful. Teams took Chapman’s lead and started researching with various materials to construct a monocoque.

In 1981, McLaren came out with a carbon fibre safety cell in their Formula 1 car. Lotus started research on composites of carbon and kevlar reinforced resin. They used the “cut and fold” methodology that would replace the pre-bonded aluminium skins in Formula 1 cars. McLaren was simultaneously conducting research on carbon fibre composites. In 1983, McLaren rolled out the MP4/1C, the first Formula 1 car with a carbon fibre moulded monocoque. The credit for designing and constructing the monocoque goes to McLaren’s main engineer, John Barnard. Although the car was originally powered by a Ford engine, McLaren later shifted to a Porsche engine. Hercules Aerospace constructed the first monocoque for McLaren.

How is a car monocoque made?

The earlier monocoques were built on two male moulds. McLaren used alternate carbon fibre layers that were interspaced with alloy honeycombs. Lotus used folded composite carbon fibre sheets in layers. The two moulds were later bonded together at the bulkheads to form the monocoque. The use of male moulds meant that the outer surface had a rough finish. But this method was adopted so that the suspension mounting points could be accurately placed. The chassis was strong and withstood the impact forces very well.

Carbon composites proved to be very resilient and constructors were satisfied with the material. All teams soon started experimenting with carbon composites to build a monocoque. The impact withstanding capacity of a carbon composites monocoque was proved in 1981. At the 1981 Italian Grand Prix, John Watson crashed his car with great force into the barriers. Watson walked away from the debris virtually unharmed. This incident reinforced the belief in the resilence of carbon composite monocoques in a crash.

In 1983, the ATS team experimented with a new way of fabricating the monocoque. They used a female mould to construct the two halves of the monocoque. The result was a monocoque with a much smoother finished outer surface. With a neater surface, ATS were able to discard the outside bodywork altogether. The car was much lighter after doing away with the outside shell of the car. Ferrari was not far behind in following this method of moulding the monocoque. The Ferrari 126C3 was built with a full carbon-composite chassis.

The advent of advanced aerodynamics meant cars started having more complex shapes. By 2000. The mould was broken into several sections or parts. These were all bonded together to form the monocoque. All teams resorted to carbon composite monocoques for their added resilience and safety. Research and experimentation on composites yielded materials with better resilience and impact withstanding capacity. The composite now used in monocoques is twice as strong as steel but five times lighter.

All the sections of a monocoque are handmade. Twelve layers of carbon fibre mats are placed, one over the other, in a mould. A carbon fibre mat is made from very fine interwoven threads. Each of these threads is five times thinner than human hair. Depending on the anticipated loads on each section, mats with different weave patterns are used in different moulds. To increase the rigidity of the monocoque, a honeycomb-patterned aluminium layer is inserted between two carbon mats.

The shell is then heated in an autoclave. An autoclave is a giant oven under negative pressure. It takes two and a half hours of heating at a predetermined temperature before the shell gets hardened. This procedure is repeated twice more to season the shell. This makes the shell strong and resilient enough to protect drivers in very severe accidents. When Giancarlo Fisichella crashed his car at the 1997 Silverstone Grand Prix, he walked away with only a minor knee injury. An analysis of the Accident Data Recorder (black box) later showed that his car came to a stop from 227km/h in only 0.72 seconds.

What tests are F1 monocoques subject to?

The FIA as well as the Formula 1 teams are tirelessly working to improve the safety of Formula 1 drivers. A monocoque made from carbon fibre composites can be as light as 35kg. Yet it tolerates fantastic cornering speeds, aerodynamic loads and very large impact loads. The FIA, along with team designers, have formulated several new rules that have to be followed before a monocoque is accepted for use. The FIA mandated several crash tests in 1985. These tests are obligatory and are getting more stringent by the year.

Crash tests for rear and side crash structures as well as rollover bar have been made mandatory since 1997. These tests are carried out before the beginning of each new season. The tests are conducted in front of an FIA delegate according to procedures laid down by the FIA. All the measuring instruments used in a crash test are calibrated before the tests. To improve safety in the sport, the FIA continuously revises the standards to be met during these tests. The requirements to be met, increase in severity every season as the speeds of the cars increase.

Carbon fibre composites can withstand great dynamic loads. The FIA is concerned about the composites’ ability to withstand penetration. For this reason, the FIA made it mandatory that the inside most layer of the monocoque be made from Kevlar. Kevlar is a strong material and is highly resistant to penetrative forces or point dynamic loads. The mandate came after Michael Schumacher’s 1999 crash at Silverstone. The front suspension wishbone had penetrated Schumacher’s car and broken his leg.

The impact absorption capacity of a monocoque is measured in Specific Energy Absorption (SEA) units. These units are measured in kJ per kg a material can withstand. The SEA of composites is far higher than their metal counterparts. The SEA of steel and aluminium are 12kJ/kg and 20kJ/kg respectively. A monocoque is a highly refined and optimised structure made of carbon fibre reinforced polymer (CFRP). It can withstand impacts from 40kJ/kg to 70kJ/kg. That is the reason CFRPs are materials of choice for constructing monocoques.

A driver sits inside a monocoque in a cramped space. To ensure that a driver is as comfortable as he can be, the FIA has imposed limitations on the dimensions of the monocoque. The FIA specifies minimum inside dimensions to ensure the driver’s legs do not get injured. There are both maximum and minimum dimensional limits for the outside of the monocoque depending on the portion. While some portions are limited by maximum dimensions, others are constrained by minimum. This is to prevent aerodynamic engineers from getting carried away with the design of the car.

Conclusion

Carbon fibre reinforced polymers are the best-suited materials for the construction of  Formula 1 car monocoques. Not only do they absorb encountered stresses, they successfully withstand very high impact loads. They are also relatively easy to mould and bond together while retaining their load withstanding capacity. Carbon fibre reinforced polymers are there to stay in Formula 1 car monocoque manufacturing. They are not likely to be replaced with another material any time soon. If anything, with continual research and experimentation, stronger carbon fibre reinforced polymers will be manufactured.

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