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This report discusses new techniques with composites that could build cars with half the weight of existing alloys. One to watch?

 

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This report discusses new techniques with composites that could build cars with half the weight of existing alloys.

Pointless in most cases.
Diminishing returns apply given heavy batteries.
 

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2020 BMW i3S 120Ah BEV
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Not that new, really. I have a BMW i3 on my drive. There's the i8, Lotus Elise, Vauxhall VX220, iirc too. Pity BMW don't seem to be pursuing future CFP cars because stupidly heavy cars is one of the biggest reasons we need so many safety gadgets in modern cars, and as battery energy density increases they will become a smaller and smaller part of the overall weight of the car thus making it far more useful to tackle weight elsewhere too.
 

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Not quite sure why you mention the Lotus and the Vauxhall, as they both use extruded and bonded Aluminium for the chassis.

Halving the weight of the body is quite feasible already if you use suitably exotic materials. What they are doing is the same thing but costing the same as an Aluminium body. 'Adding lightness' as espoused by Lotus is a virtuous circle, as a lighter body means that the springs, suspension, braking and drive components can also be lighter as they don't have to endure as much stress, lightening the car even further. The problem is that Aluminium (and therefore these composites) is already expensive for bodywork compared to steel, and EVs are already noticeably more expensive than 'regular' cars
 

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The body was CFP on both. The i3 also uses an alu chassis. Certainly true it's more expensive than steel while it's unusual, and I don't know whether the Delta would remain so significant if it became the norm. But hey, electric windows used to be expensive but are now standard. If people find a reason to want it car manufacturers would make it work.
 

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IIRC the body weight of cars is already not that much, 25 to 30% of all up mass.

So if you halve the body mass using ultra exotic materials, you have to ask yourself whether a 12% saving on total mass is worth the cost, and all the other complications with insurance damage and such.

High stressed steels, foamed metals and honeycomb metal sandwiches still have a way to go towards this before relying on awkward-to-recycle composite exotics, and will add up to much better value for money in light-weighting.

Also to note, the mass of a BEV doesn't really affect its efficiency much. Most of the high-level energy expenditure is from long distance high speed driving, and vehicle mass doesn't affect that, and for low speed work the impact of body mass is much less than ICE because of the regeneration of much of the KE back to usable energy.
 

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IIRC the body weight of cars is already not that much, 25 to 30% of all up mass.

So if you halve the body mass using ultra exotic materials, you have to ask yourself whether a 12% saving on total mass is worth the cost, and all the other complications with insurance damage and such.

High stressed steels, foamed metals and honeycomb metal sandwiches still have a way to go towards this before relying on awkward-to-recycle composite exotics, and will add up to much better value for money in light-weighting.

Also to note, the mass of a BEV doesn't really affect its efficiency much. Most of the high-level energy expenditure is from long distance high speed driving, and vehicle mass doesn't affect that, and for low speed work the impact of body mass is much less than ICE because of the regeneration of much of the KE back to usable energy.
Donald is on the money again. Total case of diminishing returns. HSLA steel is pretty much the only technology needed.
 

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High stressed steels, foamed metals and honeycomb metal sandwiches still have a way to go towards this before relying on awkward-to-recycle composite exotics, and will add up to much better value for money in light-weighting.
magnesium with sapphire whiskers?
 

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Steel is recyclable. FRC is not. They should be banned for normal cars.
Not something I've looked at before, but you're correct, carbon fibre recycling is in the early stages and not well developed. It's not impossible however and overall lifetime energy cost of using carbon fibre components for transport might easily offset any short term issues with the energy required to recycle it. There might be other ways to achieve the same thing I'm sure.

Regardless of the efficiency argument, vehicle mass makes a big difference to impact energy during accidents and for that reason alone reducing the weight of cars would be a benefit to everyone who has to get hit by them occasionally.
 

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Have a look at the teardown of the Model Y by Munro. In this episode he looks at the two large aluminium castings and a plastic moulding that Tesla have used to replace a lot of pressed steel bits that had to be spot welded together to get the equivalent function at the rear of the Model 3. I guess there might be a weight saving, and Tesla do use a mix of aluminium and steel and plastics to optimise strength and weight. But one of the main advantages seems to be that you get all the fixture points in the casting, thereby saving assembly time. Materials switches can be for other reasons than weight and can save overall costs. Skip to about 12 minutes for the castings:

 
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