Can you build a stiffer, lighter Ferrari from composite or aluminium? It's not quite that simple, reports Richard Gotch
The next generation of V8 Ferraris will have body structures that are 15-20 per cent lighter than those of today's cars but without sacrificing any of their stiffness.
Will this be achieved by using ultra-light, ultra-stiff carbon composite structures? "Absolutely not," says Ferrari's CEO, Amedeo Felisa. "In this sector of the market, we believe that aluminium is superior."
A 20 per cent reduction in body weight gives roughly a 5 per cent reduction in global vehicle weight, which means better performance, improved emissions and fuel economy.
A lighter body also means there is less mass to accelerate, steer and stop, so dynamics are improved. Ferrari has been developing its expertise in aluminium Body-in-White for more than 15 years.
"I believe we now have a world-leading capability in lightweight aluminium body structures, with more to come," says Felisa.
Carrozzeria Scaglietti is Ferrari's body assembly facility, a short drive from its main factory in Maranello, Italy. The plant has built bodies for Ferraris since 1953, including iconic vehicles such as the 250 California Spider and 250 GTO. Since being taken over by Ferrari in 1977, the facility has been transformed into a high-technology research centre and state-of-the-art manufacturing facility.
But the company's commitment to aluminium isn't just based on Scaglietti's long history of creating some of the world's most beautiful automotive bodies in the lightweight metal. Ferrari has substantial experience in composites, too - from its Formula One team and "ultimate" composite supercars, most recently the Enzo - so could create every road car from the latest carbon technology if it wished.
"Composites deliver impressive results when they are carefully hand-laid by craftsmen whose years of experience allow them to effectively manage the weave," says Felisa.
"It's hugely expensive, and has the potential for significant variability. It is also much more difficult to repair should there be an accident."
Ferrari's body systems manager Patrizio Moruzzi says: "We will continue to develop composite technologies for our ultimate cars where the overriding requirement is extreme performance.
"When we look at the requirements for our V8 cars, produced in volumes of typically two to 10 a day for owners who use them regularly, we see that aluminium is clearly the better solution and offers much greater potential for further improvement, as well as being 100 per cent recyclable."
The story began with the introduction of the mid-rear V8-engined 360 Modena in 1999, with the Body-in-White based on a spaceframe, largely built on cast and extruded structural components, to which the aluminium body panels were attached.
This technology was subsequently applied to the models in the V12 range - the 2004 612 Scaglietti and then the 2006 599 GTB Fiorano - before being updated for the new generation of V8-engined cars - the 2008 Ferrari California and the 2009 458 Italia.
In the run-up to the California and 458 Italia, research and development investment for Body-in-White technologies was increased by 50 per cent. The results were dramatic.
"This is when we started to design cars to take greater advantage of aluminium's properties," says chief engineer Roberto Fedeli. He cites the torque reaction box (at the base of the A-pillar) as an example.
Traditionally made from an extrusion reinforced by welded plates, it can now be heat-formed in a single piece. Not only is the amount of material reduced, it increases consistency and allows a greatly improved shape.
Careful materials choice, combined with developments in joining technology, allowed similar improvements across the vehicle. Five aluminium alloys were selected for extrusions and three for body panels, allowing material characteristics to be optimised for the specific requirements of each component.
The latest high-strength alloys allowed the resistance of some components to be increased by up to 80 per cent. In total, the California and 458 use more than 20 aluminium alloys.
Ferrari says its next-generation V8 cars will build on this approach. The objective is to offer at least the same space as today's cars, but with more performance, more comfort and maybe a smaller footprint.
"At Scaglietti, we are using the time between the launch of the California and the design of the next V8 to really push hard on the Body-in-White technology," says Fedeli.
"The next car will have a structure that is much more optimised to take advantage of what we now know is possible with advanced alloys."
To achieve the ambitious weight and stiffness targets set for the next-generation cars, the choice of alloys will expand dramatically. The process started with the move to aluminium lithium for the anti-intrusion beam in the doors of the 458.
Lithium atoms replace aluminium atoms within the aluminium crystal lattice but are much lighter. Introducing another size of atom also helps to block the movement of dislocations during deformation, making the material stronger.
Like many of the new materials being implemented by Ferrari, most applications for aluminium lithium have so far been in aerospace: the final version of the Space Shuttle's external fuel tanks were principally made of aluminium lithium. "We'll see a lot more in the next V8 Ferraris," says concept engineering manager Franco Cimatti.
We may also see another exotic material, aluminium silicon carbide. This is a metal-matrix composite consisting of a matrix of aluminium in which silicon carbide particles are dispersed. Integrating a ceramic - essentially the same material as ceramic brake discs - makes it extremely hard. The result is mechanical properties comparable to steel, but with a fraction of the weight.
There are also new ways of processing aluminium that are creating some exciting possibilities.
Today's Ferraris already use components with a variable wall thickness and the use of this technique will increase significantly. Traditionally, there were two ways to make the metal around a fixing point stronger: you made the entire component thicker (so heavier) or you welded on a reinforcing piece. Now, the component itself can be made thicker where necessary.
Picking up a piece of aluminium foam reveals another hidden secret: a section the size of a brick weighs just a few grams.
Typically, 75-95 per cent of the volume is just space. Changing this ratio and some other parameters allows the material to be tailored to a wide range of applications.
As well as being light and stiff, aluminium foams have good energy-absorption characteristics that make them interesting for sound dampening and for managing energy during impacts.
"Lightweight hollow box sections can resonate, and solid metals are good at transferring noise and harshness," explains Cimatti.
"Replacing selected areas of hollow section with aluminium foam could mean that we can reduce the size and weight of acoustic management systems and improve crash performance without impacting weight and stiffness.
"We are moving from simple materials substitution - where a better material replaces a traditional one - to a point where the structure is designed specifically to allow the characteristics of new materials to be fully exploited," continues Cimatti.
"There are many considerations, including how we are going to build the vehicle using the new materials.
"The answer for Ferrari is to develop new manufacturing techniques alongside our materials selection studies."
One of the biggest challenges is how to join new materials together. Very thin panels, for example, can't be welded. Neither can some very hard alloys.
"To join sheet components, we could use mechanical fixings like self-piercing rivets, but these concentrate the stresses so can require either thicker materials or the use of reinforcing sections, both of which add cost and weight," says Cimatti.
Lightweight metal foams create a new set of challenges.
The options are to use improved versions of familiar joining processes or to move to something radically different: structural adhesives.
Cimatti says the high-tech bonding system could allow down-gauging of some panels by up to 20 per cent while also increasing the body's stiffness.
Adhesives can also be used to supplement mechanical fastenings, allowing fewer welds or rivets or providing additional rigidity, thus eliminating reinforcing components.
It's likely the next-generation cars will see a lot of joints in which adhesives work in combination with enhanced riveting technologies.