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FEATURE


POROSITY SEALING Carbon fibre has become an essential teammate for F1 drivers,


helping them to achieve ever faster speeds, safely. Yet the tiniest void in components can compromise the performance of these


critical components. Gareth Ridge, operations manager at Ultraseal International, explains how porosity sealing can help


POROSITY SEALING HELPS TO PUT F1 TEAMS IN POLE POSITION


pipes, fuel tanks which must not leak too, as porosity in such components can lead to a race car retirement. Understandably, F1


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teams are well versed in the challenges surrounding pressure and fluid. The engineering talent on tap is enviable, and the teams test parts themselves. If leak paths and voids are found, then it is critical that these are sealed, so the carbon fibre components typically go through vacuum impregnation to seal the porosity. The challenge, as ever, is the geometry of parts. As the


trong yet light, carbon-fibre reinforced polymers are the composite components found in industries from oil and gas to


aerospace and even sports equipment. The use of composite materials has, in fact, been instrumental to the technological strides made in the development of Formula One cars over the past half century, where the lightness of the material helps to avoid loss of speed, while its rigidity and robustness can protect drivers during collisions. As innovations in manufacturing continue – such as 3D printing – the potential exists to build ever more complex components using carbon fibre composites. Achieving this balance of weight and


strength depends on absolute precision, however the weaving together of separate fibres means that microscopic gaps can appear during manufacturing. This tendency towards porosity must be counteracted in order to avoid air or fluid leaking from components or moisture ingress into components, compromising their effectiveness.


POROSITY SUPPORT Consider the gearboxes used in F1. These cannot be porous as this would severely impact performance and damage other critical components; and sometimes these gearboxes are worth tens of thousands of pounds. Gearboxes can be over 1m in length and a lot of time, resource and investment goes into designing and building them. Then there’s other components such as fuel pipes, oil sumps, air


5 DESIGN SOLUTIONS JUNE 2022 8


teams become cleverer in the refinement of component design, so too does new potential emerge for porosity issues. The impregnation process therefore requires the most stringent checks. This is where Ultraseal can assist.


THE DOUBLE IMPREGNATION PROCESS Based at Ultraseal’s Slough facility, the Impregnation Service Centre is used extensively to seal carbon fibre components. For components as critical as those found in


F1 cars, these are impregnated twice to ensure that they are completely sealed. Generally, the double impregnation process consists of the following sequence of steps: • Components are carefully packed in a basket and protected using Netlon to prevent damage


• The basket is placed into autoclave, where initial impregnation takes place


• Excess sealant is drained • The component undergoes a manual hand wash to remove excess sealant


• The component then goes through a hot cure process at 95˚C which polymerises the Ultraseal sealant


• The cycle is repeated to enact double impregnation on all carbon fibre parts. The cold wash is important because of the


geometry of components. A pipe could easily become blocked with sealant, therefore it must be washed out thoroughly. This is generally done manually to ensure no blockage remains. Although more labour-intensive, having a


trained operator gives customers the peace of mind that it is quality-assured. Curing takes place either in hot water –


the typical choice – or in ovens. The choice of the latter is determined by whether the carbon fibre component contains Rohacell, a honeycomb structure designed to improve the component’s internal strength. Under hot water Rohacell expands, damaging the component – therefore there is a need for an alternative curing method. Another factor to consider is the lightness


of carbon fibre components, which must be packed carefully to avoid damage during impregnation. In Slough’s two top-loading machines, each component is packed with Netlon, a malleable plastic netting that keeps components separated in the loading basket. As a result, these high value components are safe from damage without the basket load capacity being compromised.


FAST RESPONSE Physically, each impregnation cycle takes about an hour for hot water cured components, with a cool-down period between cycles. Oven curing takes around 3-4 hours for components containing Rohacell. Even so, this means that a component can be sealed and returned to the team the same day. This is, of course, critical. Everything in F1


moves super quick – not just on the circuit. The continuous improvement of components, or the need to replace damaged parts following a crash, means that a 24 hour – or even same day – turnaround is common. That’s why we react just as fast as the drivers and teams themselves and can open our Slough facility over weekends, to meet whatever deadlines the teams throw at us. F1 is an innovator, but it’s fascinating to


see how other manufacturers are taking inspiration from these innovations. As different materials and new methods of production gain acceptance, we’ll see other industries follow the example of F1. Any component that benefits from balancing maximum strength with minimum weight, will likely be manufactured using carbon fibre components – and that means the question of porosity sealing must be answered if they are to achieve peak performance.


Ultraseal International www.ultraseal-impregnation.com


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