Motorsport demands high performance and lightweight materials – historically, this has resulted in carbon fibre composites being the go-to choice.
Now though, new materials are emerging, which offer both enhanced performance and reduced environmental impact.
Driven by a combination of forthcoming regulatory changes and race teams increasing recognition of their own environmental policies, interest in these sustainable composites materials is growing rapidly.
If you missed our webinar titled “Lighter, Faster, Greener: How Sustainable Composites are Making Their Mark in Motorsport Applications”, you can watch it here… in this webinar, we’ll draw upon our extensive experience in the development and production of high-performance composites to explore the benefits on offer from sustainable composites, and highlight current and emerging applications within the motorsport sector.
We had some great questions during the webinar and couldn’t answer them all within the allocated time, so here’s a selection.
“Can you supply PFA resin prepreg based on flax fabrics?”
We do provide our PFA resin system with a wide range of reinforcements including flax, for further information please see Evopreg PFC.
“Do you have any published results for flame resistance / toxicity for the flax / PFA composites?”
Our Evopreg PFC prepregs meet the most stringent fire requirements with a glass or carbon reinforcement, you can find out further information at Fire-resistant prepregs.
“Is the PFA available as a resin and suitable for vacuum impregnation?”
Evopreg PFC is only available as a prepreg system.
“What is the best way to prevent moisture absorption. Is there any performance reduction in the case of high moisture absorption?”
The best way is to ensure that cut edges of the fibre are not exposed, for example by applying a coating of resin or some other sealer.
Regarding how performance might reduce in the event of moisture uptake, I’m afraid this is not something I have data on.
“Have any accelerated aging tests been done to evaluate long term resistance to moisture, creep or other types of deterioration of natural reinforcements? How do cured mechanical properties of furfural resins compare to epoxies, polyesters, etc? Do the cured parts retain any acidity and cause corrosion/erosion problems for adjacent contacting metallic or other parts as have older acid cure phenolics (foams, etc)?”
I’m afraid we do not have any accelerated aging test data available. If you reach out to Bcomp, they may have something which they can share.
Likewise, we do not have any data on whether PFA composite components might lead to corrosion of metal components over time. What I can say is that it is not an issue that has ever been reported to us.
Regarding the mechanical performance of PFA resin systems, the properties are more like phenolics than epoxies. Please see our technical datasheet, which has some indicative values for both glass and carbon reinforcement.
“Is there an SMC equivalent in natural fibre?”
I am not aware of a natural fibre SMC equivalent, and it is not something that is on our product development radar.
“Great technology… but how do you get B side mounting features? Do you foresee an injection moulding grade or that type of technology being developed?”
To answer the question you posted about B-side mounting features; the simple answer is that you would use the powerRibs wherever you can, but leave flat areas clear for the usual bonding of fasteners, fixing points etc.
Regarding injection moulding grades… we have done quite a lot of work on jute fibre-filled long fibre thermoplastic pellets (as an alternative to glass-fibre LFTs), and can produce small quantities on a pilot-scale for R&D trials, but we are some way from having a commercial product available.
“What is the CTE of the flax?”
The CTE of flax is very low, and closely matches that of carbon. An indicative CTE value for our Evopreg EPC300 prepreg resin (120-degree cure epoxy) on 300 gsm ampliTex flax is 10.3 μm/m/°C.
“Are cosmetic issues around PFA systems common? E.g. Class A/ trim panels feasible without extensive rework. How is flax/epoxy processed at end of life?”
PFA resins release a small amount of water during the curing reaction – in a similar way to phenolics – and therefore, even with mitigation in place, this moisture will have an impact on surface finish. So, whilst the reworking might not quite be at the same level as phenolics – it is still a requirement.
“Have trials been done to understand whether the carbon fibre can be recovered at end of life in the carbon flax hybrids? What happens to the flax in pyrolysis?”
The short answer is it’s not something we have looked at, however I would have thought they could be. I would expect the flax fibres to be destroyed in the pyrolysis.
“What is the CTE of Flax/Epoxy tooling prepreg? Is flax also suitable for combination with 350F/175C epoxy cure?”
To be honest, this is not something we would recommend. The flax fibres will start to degrade during the cure cycle, and this will only continue if the resulting part is going to be subject to elated temperatures in service. Generally speaking, we look to limit the time at temperature for flax.
You also asked about the CTE of flax. The general answer is that it is very low, and closely matches that of carbon fibre. I don’t have data to hand for our latest tooling formulations however, to give you an indication, our Evopreg EPC300 (120 degree cure component epoxy) on 300 gsm ampliTex flax has a CTE of ~ 10.3 μm/m/°C
“What is the crosslinking system used with the PFC prepregs? Standard Epoxy? Assuming that you do not isolate the PFA yourself, are there multiple suppliers for this material?”
PFC502 (and PFA resin systems in general) cure by an acid-catalysed condensation reaction, so there is no separate cross-linking component added.
Regarding PFA sourcing; you are correct that we do not manufacture the base resin ourselves. This is something we source from a single European supplier. I know there are other suppliers who either offer or are working to develop similar products.
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