The Composite Fever: An Overview
As it is known since the 5th prototype that parts as the monocoque, seat, wings and side pods are all made using composite materials.
So, as the carbon fibre enthusiasts that we are, this year was no different!
Because the FST 10e borrowed a few moulds from FST 09e, namely those of the monocoque, the first procedure carried out was their sanding and sealing, to ensure a close-to flawless surface. For the second stage – the sealing – we started out by applying a coat of sealant followed by a coat of release agent, provided by Marbocote.
The sealant used is capable of sealing very porous surfaces and works as a first coat of the release agent. This last one makes the demolding simpler.
This process is also performed on the new moulds before laminating the composite fibre.
Parallel to the treatment on the monocoque moulds, the team also prepared the moulds intended for the aerodynamic package. These were made of MDF and underwent a series of sanding and painting stages, which ensure the smoothness of their surface, as well as their endurance to the curing process. As usual, these procedures were performed at the Robbialac facilities in Lisbon as it will be the car’s final painting and varnishing!
As the month came to an end, the team was able to start working on the accumulator container that, this year, will be manufactured out of yet another well-known composite fibre – Kevlar.
Used in various applications ranging from bicycle tires to bulletproof vests, some of the properties that make Kevlar such a versatile material are the excellent strength to weight ratio as well as its thermal stability. These were the main reasons why the team chose to incorporate the fibre provided by Tei Composites on the FST 10e accumulator.
Then March came along and brought the pre-preg fun!
With the moulds ready to use, the next step was the lamination and then the autoclave curing process.
Why pre-preg carbon fibre, you may ask?
Because it allows better control over the fibre/resin ratio as well as over the out time during which the fibre can be handled without a change in its properties. Moreover, the pre-preg carbon fibre provided by Delta was also high modulus, meaning it has a high Young Modulus which translates to greater stiffness and higher resistance to deformations, resulting in lighter structures.
Truth is, we’ve been talking nonstop about fibre, but we can’t forget the cell foam we use as the core material in some of the parts on the aerodynamic package.
This cell foam comes in boards all the way from Germany. Our sponsor since the FST 07e, 3D|CORE, provides this structure in honeycomb that fits curved and complex moulds and increases the stiffness of the fibre elements.
Staying on the topic of aerodynamics, some of the parts are made resorting to composite materials that undergo an infusion process, which means that unlike what happens with prepreg fibre, the fibre used in the majority of the aerodynamic elements needs to be impregnated.
The composite reinforcement layers are applied onto a female mould followed by a sealing layer. The impregnation resin completes the wet-out by being forced into the mould by a vacuum.
As it has been since FST07e, the team is using the resin supplied by Duroplast for this process.
Finally, we get all the autoclave fun. This is without a doubt an essential stage on the manufacture of carbon fibre structures since working with composite materials is often challenging and requires a lot of precision as every little detail can have an impact on the final result.
So, Vacuum bagging films, bag connectors and houses, peel plies, breathers and bleeders and sealant tapes are all essential materials when it comes to transforming a simple roll of fibre into a formula prototype and for that, the team has been counting on Airtech Advanced Materials Group ever since the FST 06e. This year was no different!
Despite all this work being coordinated between the chassis and aerodynamic departments, both team members and recruits took part in most of the manufacturing procedures.
Fun times for all our Bob the builder alter egos, wouldn’t you say?