3D printing with polymers has been available for more than 20 years and has been used by Formula One engineers, but if you exclude the fibre-reinforced polymer composites that make up most of a modern racecar, plastics have only limited applications on the car itself.

In general, printed plastic parts have been used predominantly for mock-ups and space claim (the use of a model to represent the overall dimensions of a component, but generally without functionality, to allow other components to be designed and added to the system without interfering with existing parts), wind tunnel models and more recently for tooling in the production of components from composites. The limited structural capabilities and temperature resistance generally restrict the selection of polymers, whether 3D printed or produced via more conventional methods; however, the geometric freedom unlocked by AM and the potential advantages this can deliver make it a technology that will continue to find applications in Formula One.

This is supported by more recent developments in AM which have seen the increasing availability and capability of metallic 3D printing. This opens up a world of opportunities with the ability to rapidly manufacture components in high-performance alloys such as Inconel, a nickel-chromium superalloy, and 6Al4V titanium alloy, both commonly used in machined, cast and fabricated motorsport parts.

These opportunities have not gone unnoticed by the Formula One engineering fraternity, and techniques such as direct laser metal sintering (DLMS) and laser melting are being exploited to deliver a range of benefits that are not solely concerned with reducing weight. In fact, it is often the ability to reduce development times that make these techniques so attractive, although unsurprisingly this can come at a cost.

Some examples of metallic AM components include turbine housings that form part of the current turbo powertrain ERS systems, and at least one team has used DLMS to produce fully functional prototype housings in steel for development and testing. The parts were post-machined, as would be required for a more conventional cast version, but the build resolution and material properties offered by this technology allowed the wall thickness to be reduced by a third, from 3 to 2 mm.

The reduction in lead time and weight is significant, especially when considering the additional patterns and tooling required for casting, but with a price tag of around £20,000 (about $32,000) per housing the metal printing technology is currently still too expensive for the limited ‘production’ required by Formula One teams, even with their budgets.

Other teams have been developing titanium valve bodies for shock absorbers, and by optimising the component geometry for the printing process and understanding the design freedom and limitations, significant returns are possible.

Ongoing r&d into the printing of metallic honeycomb structures may also have some applications in motorsport. The prospect of printing cores for fibre-reinforced composite structures could offer some interesting properties, especially in crushable structures, as the core can be engineered to behave auxetically (exhibiting a negative Poisson’s ratio), potentially increasing its ability to absorb energy. (Poisson’s ratio is the negative ratio of transverse to axial strain. When a material with a positive Poisson’s ratio is compressed in one direction it tends to expand in the other two directions perpendicular to the direction of the applied force. An auxetic material, which has a negative Poisson’s ratio, exhibits the opposite behaviour, and when compressed in one direction become thinner in the perpendicular directions.

Metallic AM parts have generally exhibited properties exceeding those of equivalent cast materials, but which fall short of the performance offered by the alloys in wrought form.  The continual and rapid developments in these technologies are beginning to address this deficit though, as well as improving build resolution and surface finish.

Heat treatments for annealing and stress relief of titanium are delivering improved ductility and fatigue strength, while solution treatment and precipitation hardening (ageing) of Inconel offer improved mechanical properties, making these materials a viable alternative to machining from solid wrought alloys.

As the cost of the raw powdered alloys and machines decrease, and the capability, capacity and availability increase, the use of 3D printed components on Formula One cars will continue to rise. The early compromises regarding material properties and build resolution (wall thicknesses of 150 microns are achievable) are being addressed, offering the potential to take metallic AM technology from its niche applications in prototypes and complex integrated geometry designs to a production alternative for the small batch volumes required in Formula One.

Near-net shape printing with minimal post-machining could offer racing significant advantages in development and production times and ultimate costs, as well as all the potential performance gains that can be achieved once freed from the geometry constraints of conventional manufacturing techniques.

Mechanical properties of wrought materials

Table of AM mechanical properties (Courtesy of Renishaw)

Table of mechanical properties of titanium 6Al-4V-AM (Courtesy of Renishaw)

Written by Dan Fleetcroft

KERS systems were originally split into mechanical (flywheel) and electrical (battery) types, harvesting energy during braking to be released subsequently for shorts boosts in performance. Flywheel technology works by using braking forces to spin a mass (5 kg) at very high rotational velocities in excess of 60,000 rpm, and to improve efficiency the flywheel is housed within a vacuum. This creates sealing challenges, increasing the complexity of the manufacturing and assembly techniques to produce and build it. 

Modern Formula One engine turbos spin at even higher rates ( about 100,000 rpm) and both these and the flywheels demand incredibly high tolerances of manufacture. Bearing alignment and cooling are critical at these angular velocities, and when combined with high operating temperatures, centripetal acceleration, incredibly tight packaging and light weight there is little to no margin for error. To this end. teams have been specifying a concentricity of 1 micron (0.001 mm) on the turbo shafts to ensure alignment for seals and oil flingers, and reduce radial loading on the bearing and shaft vibration. 

It is also critical that all rotating components are dynamically balanced, with this process having to be repeated at every sub-assembly level. Accuracy of components not only has an impact on assembly but also the speeds at which these systems can operate and therefore their ultimate performance. With reliability so important in Formula One components, quality is paramount, and given the amount of energy in a spinning flywheel or turbine wheel the result of a bearing failure or clash can be catastrophic. 

The teams on this season’s grid run an energy recovery system (ERS), an evolution of the KERS, in combination with the turbocharged V6 engines. The ERS stores energy generated under braking in (lithium) batteries, and works with two motor generator units (MGUs) to convert mechanical and heat energy into electrical energy. 

The first MGU, MGU-Kinetic, uses the car’s kinetic energy to ‘charge’ the batteries, which can then in turn power the MGU-K to drive the car via the crankshaft. The second generator, MGU-Heat, is connected to the turbo and converts heat energy from the exhaust gases into electrical energy, which is again stored in the batteries and can be used to power the car through the MGU-K as well as spooling the turbo to reduce lag. 

For both generators, and the complex system they form, efficiencies and performance are related to the precision of the components and assemblies. However, there are further challenges with the manufacture and assembly of the batteries themselves. 

First there are the United Nations Transport of Dangerous Good regulations that make recommendations for the transportation of lithium batteries. These guidelines are enforced to reduce the risk when shipping these high energy-density cells, which is relevant due to the air freight requirements of Formula One’s international race calendar. This results in the energy storage batteries being housed in Zylon fibre-reinforced epoxy composite cases with integrated busbars (connectors) co-cured into the laminated components. These casings have to pass ballistic tests to ensure they are safe to ship and race. 

The next manufacturing challenge is the intricacy of the battery design. The batteries are made from multiple components in multiple materials with complex features including integrated cooling circuits, which are all critical to performance and safety. Creepage distance requires careful consideration and further complicates the design and subsequent manufacturing; it is not enough to consider the clearance distance between two conductive parts, measured through air. At high voltages a partially conducting path of localised surface deterioration of the insulating material can result in an electrical discharge between conducting components along the surface contours of a non-conducting part, a process known as tracking. This can be minimised by ensuring adequate creepage distance between these parts, but with available packaging space at a premium this is achieved by additional features that increase the creepage distance rather than simply moving conducting components physically further apart. 

Finally there is the battery assembly process. The cells are assembled on bespoke trollies, in environmentally controlled areas usually outside of the main factory. The operators are earthed and wear rubber gloves, and all other engineers authorised into the build area are encouraged to keep their hands in their pockets to avoid the prospect of a hefty electric shock. 

The reason for all these precautions is the potential for a short circuit in an ERS battery initiating a chain reaction through the cells leading to a ‘thermal event’. This reaction is exothermic and uncontrollable, and can generate enough heat to vaporise aluminium. The standard procedure to deal with an unstable battery is to move it, and hence the trolley and external workshop, as far away from buildings and people as quickly as possible! 

All aspects of Formula One push the engineering boundaries in the quest for ultimate performance. ERS and turbo technology may just be pushing manufacturing that bit harder, the prize being additional performance if components can be produced and measured with greater accuracy.  

Written by Dan Fleetcroft

The increasing complexity of the modern racecar, from both structural and aerodynamic perspectives, has led to a reliance on simulation software to evaluate and optimise designs. Materials and aerodynamic behaviour can no longer always be predicted confidently without these tools, and they offer engineers a fuller understanding of the physics governing performance.

The recent FIA restrictions on wind tunnel and track testing have further increased the dependence on simulation software, particularly CFD codes, but their use is also now limited by the technical regulations. The consequence is that Formula One engineers need optimisation tools that work faster and smarter to maximise performance in the shortest timescales.

The traditional approach for optimisation using simulation software is to evaluate the design, make geometric modifications based on the results and engineering experience, and then re-run the simulation. This design loop is repeated until the required performance is obtained, and it can be a protracted process, with the need to re-mesh and solve the models for each geometric iteration.

It is also not guaranteed that the changes implemented will produce the desired or anticipated results, with the stress distributions and flow regimes calculated not necessarily being intuitive. This can lead the design in the wrong direction, wasting time and resources on pursuing the ‘wrong’ solution. In addition, to ensure a robust solution is reached, there are many potential variables to consider, which increases the simulation overhead.

There are however some software technologies being developed that may provide an answer to these challenges and accelerate the path to an optimised design. For example, topology optimisation software can be used with FEA solvers to generate conceptual designs for lighter and stiffer structures based on ‘minimum metal’ solutions. Existing designs can be improved using shape-optimising tools that automatically modify a component’s surface geometry to minimise stress and strain, or a combination of parameters, to deliver more reliable and efficient parts. 

Similarly, adjoint solver technology can be combined with CFD codes to optimise aerodynamic performance. In standard CFD methodology, a number of inputs such as the properties of air, ground roughness and angle of attack must be described to define the problem. These inputs are then used to calculate the flow information desired by the engineers – for example, vortex shedding, exhaust gas mixing, brake cooling and so on. Adjoint technology reverses this approach though, and effectively asks how the input variables can be altered to effect a particular change in the output results. For a racecar, geometry represents one of these input parameters, so by exploring how the shape of a front wing, say, must be altered to increase downforce, the adjoint solver – coupled with a tool to automatically ‘morph’ the surface geometry – can deliver an optimised solution after it has evaluated multiple geometric options.

Fig. 1 shows the improved downforce-to-drag ratio achieved using adjoint solver technology to modify the endplate geometry of a simplified Formula One front wing in a straight-ahead position. In reality, on track the car experiences a multitude of conditions, from ride height and speed changes to varying cornering rates, so to give a robust and optimised solution all these permutations need to be considered by the solver. If it is assumed that during a lap the car’s geometry is fixed then the circuit’s characteristics can be condensed into a probability density function (PDF) that is then used as an input into the adjoint solver.

Fig. 2 shows a graphical representation of all steering angles and velocities experienced by the car around a lap of Monza, and characterises the track’s unique identity (for these parameters). This PDF is then used to sample design points for the adjoint solver where steering angle and free-stream velocity are adjusted for each point. A mean value penalty (MVP) distribution is selected such that the downforce-to-drag ratio is significantly shifted for the entire range of defined steering angles and velocities to provide an improved performance over the entire lap, as shown in Fig. 3.

The geometry is automatically morphed in the software, and the blue wing in Fig. 4 shows the optimised design that corresponds to the density function shown in blue in Fig. 3. This wing is optimised for a particular track, not a single condition, and the changes implemented by the adjoint solver would have been difficult to predict in advance.

There are of course some challenges to overcome before topology optimisation and adjoint solvers become mainstream tools in an engineer’s development toolbox. For example, there can be issues with the optimised geometry generated, resulting in designs that are difficult or impractical to manufacture, although these are already being addressed, with parameters such as production costs being used to influence the optimisation process. There is also the challenge of exporting the optimised geometry back into the CAD packages so that it can be engineered for manufacture.

Questions may be asked regarding whether these tools are eroding the skills of the engineer, but ultimately it will be the engineer’s knowledge as to how to define the input parameters and boundary conditions, and their ability to interpret and evaluate the results, which will make these tools valuable.

These optimisation technologies are starting to provide real opportunities for accelerating the development and optimisation of designs, and look set to provide a significant competitive advantage to the Formula One teams that adopt them.

Fig. 1 - Improvements in downforce-to-drag ratio using an adjoint CFD solver on a generic Formula One front-end geometry

Fig. 2 - Derived density function for the Monza track

Fig. 3 - Downforce-to-drag density functions for the baseline geometry (red) and optimisation wing geometries (blue)

Fig. 4 - Blue wing showing the optimised geometry against the baseline design (in red) corresponding to the density function in blue in Fig. 3

(All images courtesy of Ansys UK) 

Written by Dan Fleetcroft

The competitive advantage of any performance gain – combined with the large budgets, a pioneering engineering attitude and potential global exposure – makes racing an obvious customer for the latest technologies.

The development of composite materials is relentless, with new fibres and resin systems offering improved mechanical and thermal capabilities, among other advancements coveted by Formula One engineers. However, one less obvious area of development has been in the design of the weave for composite fabrics. Most Formula One components are traditionally manually laminated using continuous pre-impregnated (pre-preg) carbon fibre reinforcements with either unidirectional (UD) fibres or woven fabrics, often referred to as cloth.

Conventional cloth weave designs commonly include plain weaves, 2 x 2 twills and satin weaves. Each of these have different draping properties (the desirable ability of the pre-preg to conform to the mould tool’s surface geometry), different levels of crimp (the undesirable distortion of the fibres produced by the interlacing of the warp and weft tows detrimental to mechanical performance) and provide varying degrees of ‘wet out’ (resin impregnation of the fibre reinforcements) and surface finish smoothness. The combination of characteristics in each individual weave style all have some level of compromise, and this has driven the research and optimisation of weave design.

Advances in textile engineering and manufacturing have resulted in the development of spread tow fabric (STF) materials. Instead of ‘bundling’ the carbon fibres in narrow and thick tows, spreading the fibres into thin and wide tapes and then weaving these together allows ultra-lightweight fabrics to be produced. This offers a number of benefits over the more traditional cloth designs.

The flat structure of STFs reduces the crimp angle and frequency while improving the resin wet-out (cover factor). This results in high fibre volume fractions with straighter fibres, increasing the mechanical properties of the laminate while reducing the amount of excess resin, therefore minimising weight.

Weight savings of 20-30% are achievable over conventional woven composites with thinner laminate thicknesses*, giving mechanical performance similar to a cross-ply construction made using UD tapes but with improved drapability and delamination resistance. The tables here give a comparison of crimp ratio between a conventional plain weave fabric and a spread tow material.

STFs deliver improved surface smoothness by reducing interlacing points, increasing fibre float and minimising crimp. This improves the aesthetics of the composite and, more important, offers the potential elimination of ‘print through’ of the weave pattern when the moulded surface is lacquered or painted. Figs. 1 and 2 show a standard plain weave fabric [Fig. 1] and a spread tow fabric [Fig. 2] which have been consolidated under a vacuum to highlight the benefits of the reduced crimp on surface smoothness. It is clear to see the flatter surface produced by the spread tow material.

Ultimately the significant weight savings, improved mechanical properties and thinner laminates are why STFs have found a home in Formula One racing cars, with many components – including the monocoque, bodywork and floors – benefiting from the superior performance this composite offers.

The constant pursuit of performance from both the racing teams and the companies who supply them drives the exploration of all potential advantages. STFs highlight how an obsessive attention to detail and comprehensive understanding of composites can take a seemingly small development and deliver significant performance returns. 

Plain woven standard fabric crimp (%) 

 Tape Woven – spread tow fabric crimp (%) 

 Crimp ratio information provided by Sigmatex 

Reference

* http://www.netcomposites.com/guide/spread-tow-fabrics/118

Fig 1 - Plain weave fabric (Courtesy of Sigmatex)

Fig 2 - Spread tow fabric (Courtesy of Sigmatex) 

Written by Dan Fleetcroft

The original process is called SLA (Stereo Lithography Apparatus) and soon became known as Rapid Prototyping (RP). The early materials had limited stiffness and stability, so their applications were predominantly restricted to prototype production, but this did not prevent the technology offering solutions in Formula One. RP components found favour on wind tunnel models, where they deliver significant time savings over the carbon fibre composite parts, and their associated dependency on tooling, that were traditionally used.

These SLA parts were generally restricted to model underbody components, due to the limitations in their material properties, until around 2005 when ceramic-filled SLA became available. This offers greatly increased stiffness, and improved dimensional accuracy and stability. Combined with the increase in ALM machine-build volumes this has resulted in most carbon composite bodywork being replaced by SLA on current wind tunnel models.

These improved properties also provide alternative applications, with SLA-mould tools being used for laminating carbon fibre components. In 2010 the introduction of Fused Deposition Modelling (FDM) soluble materials opened up even greater opportunities. Here, soluble cores can be made using ALM, wrapped in carbon fibre pre-preg fabrics and cured in an autoclave. It is then simply a case of dissolving out the tooling core to leave the component.

This approach allows a design freedom to create complex integrated geometries that would be impractical or impossible to manufacture with conventional composite tooling methods. For example, ducting and pipe designs are no longer limited by the need to ensure that the component releases from the tooling, and the challenge of maintaining structural continuity across mould tool split lines is removed.

Although there has been widespread use of ALM in Formula One, SLA components have not been used directly in racecars. Unsurprisingly, given the importance of reliability, this technology has been adopted with caution. There is possibly a subconscious reluctance and scepticism to using plastics, which is a little ironic when considering the current predominance of polymer composites. However, this is not totally misplaced as it takes time to gain confidence in new technologies and materials, particularly if they are used in ‘mission critical’ systems.

The development of ALM has been rapid, with the evolution of different build technologies and materials offering engineers greater opportunities to use these processes. Selective Laser Sintering (SLS) is another mature process that offers greater strength and temperature resistance than SLA. The development of carbon-reinforced SLS materials in 2004, with their superior stiffness and strength-to-weight ratios, paved the way for ‘on-car’ applications. These days wings, ducts and brake caps are routinely manufactured using ALM Carbon-SLS.

It is not simply the accelerated ability to takes parts from concept to racetrack where these processes deliver a competitive advantage. Replacing a carbon composite part with Carbon-SLS presents real benefits when the design is optimised for the technology. By exploiting the freedom in design offered by additive manufacturing, components can be made more efficiently by integrating features and functionality such as cooling channels, bores, threads and cores.

Free from the constraints of conventional machining, finite element analysis and topology optimisation can be used to determine where the stresses in a component are and then place the minimum volume of material to withstand these loads. This results in component geometry that places material only where it is required and not a result of the physical or financial limitations of the manufacturing process.

The use of ALM in Formula One can only rise as continual development provides higher performance materials and greater manufacturing accuracy. New materials such as PEEK-HP3 boast fire and chemical resistance, and Direct Metal Laser Sintering (DMLS) processes using metallic alloys such as titanium promise multiple applications throughout the racecar.

However, as with the transition from aluminium to carbon composites in the early 1980s, it is vital to understand the material properties and limitations to deliver the greatest advantages. Perhaps to an even greater extent than with composites, ALM requires a change in engineering thinking to realise the full potential this technology has to offer.

Fig. 1 - Carbon-SLS Brake Duct Bracket used in the brake duct assembly of a Formula One car (Courtesy of Graphite Additive Manufacturing and Andreas Anedda)

Written by Dan Fleetcroft

To this end, carbon fibre reinforced polymer composites (CFRPs) have always had a certain mystique about them. This is due in part to the relative newness of the material (compared with the maturity of metals), the complexities of design and manufacturing and the high material and production costs. It is also something that some engineers are happy to encourage.

Composite knowledge has always been a valuable commodity in racing and is becoming highly desirable in many industries. Composites now have significant commercial value – they are ‘mainstream’ and are very fashionable.

This shift has been driven by the global quest for efficiency, and in particular the aerospace industry’s leap from aluminium to composite airliners. The need for larger volumes and lower costs are advancing composite development outside of Formula One and with perhaps even greater challenges to overcome. Machining is of prime significance, and the knowledge created in Formula One is finding its way out and being developed further.

The fundamental guide to machining composites in Formula One is simple – avoid if possible. This is a sound approach in racing for many reasons. First, you have to create a mould tool in which to laminate your component. This is generally an order of magnitude more expensive to produce than the part itself, so rather than machining features as an additional operation, the goal is to ‘mould in’ all the desired geometry.

Second, composite assemblies are a challenge. Joining metallic components has well established techniques, such as welding and bolted or riveted joints. With CFRPs though, welding is not possible and the anisotropic properties of the material can make mechanical joints unreliable without a proper understanding the composite’s characteristics. This has led to the development of bonding technologies where structural adhesives are used to combine two or more composite and metallic components.

This can produce joints where the adhesive bond line is actually stronger than the matrix of the composite itself, but its success and repeatability relies on meticulous preparation of the bonding surfaces, control of the bond line thickness and thorough execution of the bonding procedure. Ironically, bonding composite parts often required the machining of the joint surfaces as part of the process.

So Formula One engineers look to reduce the part count, and therefore the need for joints, by designing integrated composite structures. Not only does this remove the need for bonding and machining, it often saves weight, improves component stiffness, can optimise the load paths though the structure and can reduce cost and manufacturing time.

Inevitably though, the need for machining is always present as the Formula One car cannot be manufactured as a single CFRP component. The cars are highly adjustable, parts require replacing and ultimately composites are not always the material of choice for every component.

Most composite machining in Formula One is driven by the need for precision. Moulding cannot always deliver the accuracy required for ‘close tolerance’ mounting features, whereas machining can.

These mounting positions often require ‘hard points’ with homogenous properties. This is generally achieved by adding machined quasi-isotropic CFRP ‘stock block’ inserts that are either co-cured or cold bonded into the laminate and then post-machined.

Machining composites is just like machining any material; the trick is learning how to do it accurately and efficiently. It does however present some additional challenges over those encountered with metals. Below is a list of the major challenges that composites pose and some of the current solutions that have been demanded by Formula One and latterly other industries.

Dust: Aside from inexperience with composites, this is probably the biggest obstacle preventing a machine shop from offering CFRP machining services. The dust can accelerate machine tool (mill or lathe) wear, requiring increased servicing and maintenance, and is a challenge to clean, especially if the machine cuts other materials with the aid of coolant. This is best addressed with an extraction system.

Tool life: Composites are highly abrasive, which leads to rapid tool wear and frequent tool changes. The solution to this is to use polycrystalline diamond (PCD) cutters, which offer dramatically increased tool life over standard carbide cutters as well as improved surface finishes.

Surface finish: The best finish is achieved using PCD tools, as mentioned above. However, machining strategy, cutting speeds and feed rates, and depth of cut also influence the surface quality (as with metals). When surface milling a technique called Sturtz milling [Fig. 1] – where an end mill cutter is tilted (between 2° and 20°) replacing the more traditionally used ball nose tool – can offer improved surface finishes and higher material removal rates.  It is also important that the strategy selected considers the heat generated whilst machining. If the surface temperature becomes too high damage can be caused to the polymer matrix as it will soften and depolymerises.

Delamination/splintering: These are the most common problems encountered when edge milling (profiling) CFRPs, and occur when the cutting forces damage the edge of the component as carbon fibres are broken out of the matrix [Figs. 2 and 3]. This can be countered by using a compression router end mill [Fig. 4], which is designed with both positive and negative helix angles simultaneously compressing the top and bottom edges of the part to reduce splintering.

Multiple materials/different properties: Another challenge with machining CFRCs is related to the very definition of the material – a composite. The composite can be constructed from a combination of carbon fibres with different properties (modulus and strength), different fibre types (glass, aramid, zylon) and/or metals such as titanium.

The different characteristics of each material affect the machining strategy and can result in a compromise. For example, when drilling composite-titanium stacks a phenomenon known as composite erosion can occur. This is the radial deterioration of the composite material exit surface caused by the evacuating metallic chips (also known as swarf) during drilling [Fig. 5]. A technique called micro-peck drilling can be used to reduce this erosion and minimise the burrs on the metallic exit surface. It works by applying periodic low-frequency axial motions during drilling to produce smaller chips, resulting in improved chip evacuation.

There is extensive ongoing r&d into composite technologies, including machining. Techniques and tools are evolving to meet the increasing demand and applications for these materials. Interestingly, as composite applications increase outside of Formula One the results of this development are more readily available, and as a consequence composite manufacturing is being perceived much more as science and much less a ‘black art’.

Fig. 1 - Sturtz Milling (Images courtesy of Sandvik Coromant)

Fig. 2 - Delamination

Fig. 3 - Splintering

Fig. 4 - Compression router end mill

Fig. 5 - Composite erosion in a stack 

Written by Dan Fleetcroft

Thanks to its highly competitive culture and substantial budgets, Formula One has always been at the leading edge of software technology, embracing the latest software tools in pursuit of every performance advantage. These range from weight reduction and improved aerodynamic efficiency to decreased development and manufacturing times and costs.

The evolution of the Formula One car closely follows that of the software tools used to create them, and their impact on performance should not be underestimated. Computer aided engineering (CAE) software provides the design freedom, evaluation and historically limitations to conceive and realise the complex geometries, structures and mechanisms that create the cars.

It is also important to consider that design and manufacturing are inextricably linked, as the design solutions that evolve must be realisable under tight timescales to ensure that the teams are on the grid when the lights go out on a Sunday.

This drives the software tools available. Computer aided design (CAD) software began replacing the drawing boards in Formula One drawing offices more than 25 years ago, and became ubiquitous in the early 1990s. It empowers engineers with a vast selection of design tools to explore, develop, refine and communicate their ideas and solutions.

It would be pointless, however, if these could not be turned into physical parts, so manufacturing technology has had to keep pace with design. Computer aided manufacturing (CAM) software allows the complex CAD model geometries to be translated into languages that computer numerical control (CNC) machine tools convert into precise movements. This allows engineers to generate machining programs and strategies to produce the parts designed in CAD that could not be made manually.

It would be possible to focus on specific commands in CAD or CAM, for example the surfacing functions used to create the complex aerodynamic surfaces, and analyse the impact they have on performance. However, to highlight just how reliant on software Formula One has become, it is worth exploring some of the other programmes used in the design and manufacturing processes.

Simulation software enables engineers to test and evaluate their designs in a virtual environment. Finite element analysis (FEA) and computational fluid dynamics (CFD) codes give feedback on structural integrity and aerodynamic efficiency, allowing multiple solutions to be analysed quickly and without the cost of physical testing in the laboratory or wind tunnel.

These tools are continually evolving to deliver better correlation with ‘real world’ testing and are now combined in ‘multi-physics’ packages. These simulate the interaction of different forces, such as mechanical and fluidic, achieving a higher fidelity with reality to give engineers greater confidence in the results.

Advanced lap time simulators model the entire Formula One car’s dynamic system, from tyre characteristics and suspension geometry to engine and aerodynamic performance. These can be used to assess the influence of a new mechanical design, changes in the centre of gravity or new tyre compounds – to name but a few – without the need for physical components and track testing, reducing development time and costs.

Dedicated software tools are also available for design and production with specific materials. Unsurprisingly, with the prolific application of composites in Formula One, one such example focuses on these materials, offering the ability to assess the lay-up by simulating draping and actual fibre orientation, which can then be used to improve FEA studies. This software also produces laminate manufacturing information including ply books, flat patterns for ply cutting and can be used with laser ply-alignment systems to assist the laminators positioning the composites in the mould tool for improved quality.

Design and manufacturing in Formula One is a complex multi-disciplinary process which involves large teams of engineers working with large and varied data sets that all need to integrate seamlessly to deliver the ultimate performance solution in the minimum time.

Collaboration, data management and project planning are paramount to winning races, and this is controlled by project lifecycle management (PLM) software. PLM integrates people, data, processes and business systems and is, in part, a software program to manage all the CAE tools and their outputs.

This diversity of applications highlights how reliant on software the Formula One industry is. It influences every aspect of the business and car, from concept through to the chequered flag. The design and manufacturing processes are all driven by software tools, and as their capabilities advance, the engineers use them to push the performance boundaries.

Fig. 1 - Rear wing end plate tooling CAD/CAM model with cutter path visualisation

Fig. 2 - Brake cooling duct tooling CAD/CAM model with cutter path visualisation

Written by Dan Fleetcroft

The superior specific strength and stiffness of CFRP to that of metals (Table 1), as well as its formability, have made it the primary choice for highly loaded and aerodynamically optimised components of the modern Formula One racecar. More and more parts have evolved from metallic to composite construction as the teams’ engineers fight to reduce weight. More than three-quarters of a contemporary Formula One car’s volume is now made from CFRP, while it accounts for less than a third of its mass.

So as this material offers such performance benefits, why aren’t even more components constructed from carbon composite? Outside of Formula One, the greatest obstacle would be cost (design, materials and production), but in the highly competitive world of motor racing this is unlikely to be prohibitive. The technical regulations restrict the use of materials for certain components, forbidding the application of composites in some areas, but one of the major limiting factors is structural integrity at elevated temperatures above 400 C.

Carbon fibres themselves have very high temperature resistance (carbon sublimes at above 3000 C); however it is the polymer matrix that limits the ultimate operating temperature of the composite. The predominant matrices are thermosetting polymers, examples being epoxies and polyesters, with Formula One composites being dominated by the former.  Epoxy systems exhibit maximum glass transition temperatures (Tg) of around 180 C above which the matrix softens, taking on a rubber-like state, greatly reducing the load-carrying capability of the composite. There are alternative polymers, including bismaleimide (BMI) and cyanate ester, which can achieve transition temperatures of up to 380 C.

Less widely used thermoplastic matrices consisting of polymers such as PEEK (polyetheretherketone), polycarbonate and PEI (polyetherimide) offer transition temperatures of up to 215 C. These again are incapable of continuous exposure to the high temperatures experienced by some Formula One components, such as the exhausts and brake discs, which can both encounter temperatures in excess of 950 C.

Composites have been used for brake discs and pads in the form of carbon-carbon (carbon fibres reinforcing a carbon matrix) since their introduction by Brabham in 1976, operating at an average temperature of 650 C and peak temperatures of around 1000 C. This material offers suitable properties for the exhaust system, but unfortunately its production method is not viable for the complex geometry.

This has meant that Formula One exhausts have remained metallic, fabricated from a superalloy called Inconel. This metal was developed for aerospace applications, and retains its high strength at over 1000 C. It has a higher density than steel (0.00844 g/mm³ compared with 0.0078 g/mm³) and to save weight it is used in thinwall sheets between 0.7 and 1.2 mm thick. This exposes the exhaust system to high stress levels and fatiguing, ultimately leading to the formation of cracks which can result in retirement from a race.

There are alternative composite materials available, or in development, that could supersede this superalloy, reducing weight and increasing the life of the exhaust. Metal matrix composites (MMCs) and ceramic matrix composites (CMCs) are offering engineers superior specific mechanical properties in high-temperature environments. 

CMCs currently offer the best potential for use in a Formula One exhaust system. There are various materials available, including alumina matrix reinforced with ceramic oxide fibres and glass-ceramic matrix reinforced with silicon carbide (SiC) fibres, with densities between 0.00185 and 0.0028g/mm³. These can be laminated using predominantly conventional polymer composite techniques in complex geometries, and can resist long-term exposure to 1000 C and brief exposure to even higher temperatures. They also offer improved thermal management properties over Inconel, with a thermal conductivity an order of magnitude lower (0.9 W/mK compared with 9.8 W/mK for Inconel 625).

There is still development to be done before CMCs will replace all highly loaded high-temperature metallic components such as the exhaust, and Formula One will need to gain confidence in these materials. Access to CMCs can be restricted, with some designated as strategic materials, but demand from the aerospace industry is high, where it is believed they will deliver considerable benefit to jet engine performance. This will ultimately drive development, making CMCs a practical material choice for engineers.

Fig. 1 - Comparison of mechanical properties of metallic and composite materials

Fig. 2 - Prost Grand Prix AP04 2001 Formula One Championship car’s fabricated Inconel exhaust system

Written by Dan Fleetcroft