"Light weighting is the final frontier in the automotive industry fight to lower emissions."


Flash bainite, a new cheap heat treated steel, looks poised to help cut some serious lbs out of future cars. Almost sounds too good to be true.

http://www.gizmag.com/flash-bainite-automotive-testing/40774/

269edb8238580efd2fe390057527c0f3.webp
 
As far as I could understand, Bainite (non-Flash) is already in use by the automotive industry in some critical components and is obtained from appropriate steel alloys after they are subject to a heat treatment process known as 'Austempering' to form Bainitic steel, which was pioneered in the thirties by Edmund S. Davenport and Edgar C. Bain (hence the name Bainite).

So, the technology is far from being new. However, the innovation with the Flash-Bainite seems to be not the material's microstructure per se, which is still a controlled mixture of Bainite and Martensite (a microstructure phase that forms at lower cooling temperatures than Bainite), but the heat treatment process itself.

Basically, whereas Bainite is formed from heating an appropriate steel alloy to a temperature of typically 900 °C long enough to give it the adequate microstructure (prior to cooling) - in steels this may take a few minutes after the temperature has been reached throughout the part section - and then cooling it fast enough at the desired quenching temperature for some extended period of time so that the final hardness and the material properties are determined by the cooling rate and the holding time, the Flash-Bainite, however, not only is formed from regular steel, instead of costly alloyed steel, but also undergoes a very rapid heat treatment process where the steel is induction-heated first to a temperature close to 1100 °C and then water-cooled in a manner that it only takes 10 seconds or so for the whole heat treatment process to be completed (hence the name Flash).

So, the Flash-Bainite is essencially a cheaper method of producing Bainite - it uses cheaper regular steel, is very fast, in a matter of seconds, with rapid heating and cooling (it consumes less energy per kilogram of steel processed), and uses water, which is cheaper, instead of oils or a bath of liquid nitrite-nitrate salt for cooling duties.

It's precisely this kind of cost reduction that needs to be applied to a manufacturing process capable of producing an 'affordable high volume carbon fiber chassis structure'. Would be very nice to see a comparison between Bainite and carbon fiber on that graphic above! ;)
 
------------ Specific tensile strength of various materials----------

..........................Tensile........ Density..... Specific...... Breaking
..........................strength...... Density..... strength..... length
..........................(MPa)......... (g/cm³)..... (kN·m/kg).. (km)

Stainless steel....... 505............. 8.00.......... 63.1........ 6.4
(304)
Aluminium alloy..... 572............. 2.81.......... 204......... 20.8
(7075-T6)
Bainite.................. 2500........... 7.87.......... 321......... 32.4
Carbon fiber ......... 4300............ 1.75......... 2457........ 250
(AS4)



As you can see, carbon fiber not only has the highest tensile strength and specific strength but also is considerable lighter (the lowest density) than Bainite.

So, carbon fiber is lighter than aluminium and stronger than Bainite.
 
It's costly to produce and costly to process!

Not really. Mass production can make CFRP production very cost effective. Kudos to BMW for proving that.

The other half story is with creep strain, heat resistance, multiple failure mechanisms that are difficult to predict in multi-axial stress, huge uncertainties considering fatigue resistance (even a simple uniaxial tension S-N curve for a simple, couple of layers CFRP plate is a hilarious joke), connections, etc

;)
 
Not really. Mass production can make CFRP production very cost effective. Kudos to BMW for proving that.

Don't make me laugh! It's like saying Tesla mass produces electric cars.

There's yet to exist a manufacturing process capable of producing an 'affordable high volume carbon fiber chassis structure'.

Affordability is the key word here. That's the sole problem with carbon fiber.
 
Affordability is the key word here. That's the sole problem with carbon fiber.

Are you kidding me?

Didn't you just read post [HASHTAG]#46[/HASHTAG]?

Do you selectively ignore what you don't like or do you want an extensive write up on why CFRP is not the wondrous material you think it is?
 
Are you kidding me?

Didn't you just read post [HASHTAG]#46[/HASHTAG]?

Do you selectively ignore what you don't like or do you want an extensive write up on why CFRP is not the wondrous material you think it is?

Carbon fiber would be wondrous if it was affordable, but it is not.

The question is: why isn't carbon fiber affordable for the automative industry?

If you try to answer to that question you'll necessarily find the problems associated with the carbon fiber production and processing. That's obvious!

But, just like with the electric cars which are still way too expensive in order to be competitive with their petrol/diesel counterparts (there's major issues to overcome that are still being addressed), the possibilities are endless and they represent the future, whether one likes it or not!!!

Carbon fiber is definitely a wondrous material for F1 and motorsport in general, as it is for my Alfa Romeo 4C and electric cars (to compensate for the batteries overweight and help extend the car's autonomy), but those are expensive, low volume cars.

So, the BIG challenge today for the automotive industry is to find a manufacturing process capable of producing an 'affordable high volume carbon fiber chassis structure', which also plays a major role in the whole car's electrification strategy.
 
Up next: Lamborghini's forged composite

"The benefits of this production method are: flexibility of producing complex parts from molds, extremely short curing time, cost reduction, and strength equal to or better than titanium at only 1/3rd the density. Curing time in a typical carbon fiber pre-preg production takes 6 hours, "Forged Composite" takes just under 9 minutes. Total production costs for "Forged Composite" are reduced by a staggering 30% compared to the production of the typical carbon fiber sheet."

http://lamborghininewportbeach.blogspot.com/2015/01/what-is-lamborghinis-forged-composite.html

a detailed review regarding the development of FC control arms for the Sesto Elemento concept
http://www.quantumcomposites.com/pdf/papers/2011-ASC-montreal-forged-suspens.pdf
 
Forged composite (...) strength equal to or better than titanium at only 1/3rd the density.


If we add the Titanium to the table above we can see that even Bainite is much stronger than it (although much heavier). So, the so-called 'Forged Composite' is still significantly weaker than Bainite:



------------ Specific tensile strength of various materials----------

..........................Tensile........ Density..... Specific...... Breaking
..........................strength...... Density..... strength..... length
..........................(MPa)......... (g/cm³)..... (kN·m/kg).. (km)

Stainless steel....... 505............. 8.00.......... 63.1........ 6.4
(304)
Aluminium alloy..... 572............. 2.81.......... 204......... 20.8
(7075-T6)
Titanium............... 1300............ 4.51.......... 288......... 29.4
Bainite.................. 2500........... 7.87.......... 321......... 32.4
Carbon fiber ......... 4300............ 1.75......... 2457........ 250
(AS4)



Like I've said, with carbon fiber the possibilities are endless and manufacturers can always choose the trade-offs that best suit them, between manufacturing time and cost, and the final product's desired charecteristics.


On another note, in one of the above links one can read: "The Lamborghini Aventador features a complete carbon monocoque with front and rear subframes of aluminum."

Actually, they could have been talking about the Alfa Romeo 4C... Nice!!!:D
 
These have to be the most relevant cars in terms of performance/fuel-efficiency state-of-art for Petrol, Diesel and Hybrid. To my knowladge, only two of them don't use carbon fiber, whether extensively or in some part(s), and only one of them uses a combination of very high strength steel, aluminum and magnesium alloys with composite materials in its platform:


High performance Hybrid (racing) Sport coupe & Petrol 4-seater (drift) Sport coupe (both use carbon fiber)
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High performance Diesel 4-seater (drift) Sport coupe (doesn't use carbon fiber)
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High performance Hybrid 4-seater (racing) Sport hatchback (doesn't use carbon fiber, uses high strength steel, aluminum, magnesium alloys and composite materials)
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High performance Petrol (racing) lightweight Sport coupe (uses carbon fiber)
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You still choose to ignore all the engineering concerns.

No. I'm just trying to show you that despite any 'engineering concerns', carbon fiber still is the material of choice when it comes to state-of-art car applications. It's inevitable!
 
No. I'm just trying to show you that despite any 'engineering concerns', carbon fiber still is the material of choice when it comes to state-of-art car applications. It's inevitable!
With all due respect, all I get is a kind of naive approach with childish level arguments.

I don't know your background, but it clearly has nothing to do with engineering. You can't expect to convince people with a few road tests, arguments like "this car has CF, that car doesn't" and a table of specific strength of various materials.

As I already told you twice, specific strength not even half the truth. It's more like a quarter. You still have to take into consideration the modulus of elasticity of your material, your ultimate strain, the fracture energry, the failure types and many many more parameters which, obviously, don't mean anything to you so you choose to ignore.

And on top of that, how (to use your words) the most state-of-the-art application of such composite materials, which is the aviation industry, threats the said materials has absolutely nothing to do with the automotive industry. We are talking about a safety factor of 1.2 in the first case and 4~5 in the second. What Boing does to a 787 Dreamliner ever some thousand flight hours is a complete C-scan. Alfa Romeo just changes your engine oil. The difference is vast and when it comes to composite materials, automotive applications are not exactly state-of-the-art. They are more like trial and error.

:)
 
@Giannis,

I will leave the personal remarks aside, it's the only mature attitude to have.

Regarding state-of-art car applications - after all it's a car forum (and a very german one, for what I can tell :D) - I could talk about F1 forever and that alone would settle it down, but since I drive no F1 car, my main concern is always the best performance/fuel efficiency result for a road going car that I can afford. So, the road tests only serves to give some idea about the performance side of such cars.

As for different car's materials characteristics, specific strength was the technical argument presented in favour of 'Flash' Bainite for future car applications - ''Almost sounds too good to be true'', just to quote someone else's post - and a specific strenght comparison table for different metals was shown in that post. Adding carbon fiber, which is already used in state-of-art car applications for some time now (we can go back to more than thirty years ago) to such a table only serves to show how far away those metals are from carbon fiber in that regard - there's a reason for F1 to extensively use it, instead of any metal!!!

Now, since you've brought up aviation to the table and since the problems with the manufacturing of airplane parts due to the relatively new processes used to make CFRP components are so BIG, why aerospace engineering even bothers to go down that route?! Isn't the carbon fiber's specific strenght advantage so huge that makes the investment worthwile?!

Besides, you seem to forget a very basic difference between cars and planes... you see, planes aren't supposed to endure crashes and collisions with each other. Does your engineering background understands this or do I need to explain it to you like you had none?!:D
 
I could talk about F1 forever and that alone would settle it down

How and why are advanced materials used in F1 is indeed an exciting topic, but sadly on of which I have limited knowledge. Given, though, that the lifespan of an F1 car and a consumer automobile is as comparable as apples and oranges, I doubt that it would, alone, settle everything and forever.

my main concern is always the best performance/fuel efficiency result for a road going car that I can afford.

Good.

So, the road tests only serves to give some idea about the performance side of such cars.

Sure, but roadtests are worthless when it comes to materials. How they behave, advantages, disadvantages, better alternatives. Unless roadtests these days take place in a structural lab and I've been completely clueless all this time.

As for different car's materials characteristics, specific strength was the technical argument presented in favour of 'Flash' Bainite for future car applications - ''Almost sounds too good to be true'', just to quote someone else's post - and a specific strenght comparison table for different metals was shown in that post.

And why was Bainite's specific strength brought up in the first place? Because that's where Bainite is competitive. And then GFRP's specific strength was brought up for comparison. And that's only one of the tens of relevant parameters.

Adding carbon fiber, which is already used in state-of-art car applications for some time now (we can go back to more than thirty years ago) to such a table only serves to show how far away those metals are from carbon fiber in that regard

Once again, a comparison table regarding the specific strength of various materials covers only one parameter. There are many more.

Now, since you've brought up aviation to the table and since the problems with the manufacturing of airplane parts due to the relatively new processes used to make CFRP components are so BIG, why aerospace engineering even bothers to go down that route?! Isn't the carbon fiber's specific strenght advantage so huge that makes the investment worthwile?!

Certainly. But at the same time, it shows that the material (CFRP) isn't perfect yet. If it were, then we would fly around in all-CFRP planes, which wouldn't need such an extensive inspection every some number of flight hours. Yes, the material is promising, but noone has complete and blind confidence to it.

Metals, on the other hand, have proven themselves over the years and man's understanding of every failure mechanism is outstanding. The accuracy of computer models and calculations, too.

There are still too many uncertainties with CFRP.

Besides, you seem to forget a very basic difference between cars and planes... you see, planes aren't supposed to endure crashes and collisions with each others. Does your engineering background understands this or do I need to explain it to you like you had none?!:D

Cute.

Seriously now, collision is just a load case when designing a car (or a plane). Surviving 20 years on the road is another load case - an equally important one - one that F1 doesn't care about ;)

I, for one, need to be sure that my car won't fall apart after some years of usage. So far, I've managed to stress one for 25 years and it's still going strong. CFRP still has to prove itself.

Sidenote: Just for the record, the Airbus A380 is designed to withstand a landing without it's landing gear, so yes, planes take impact into consideration as well.

I want to know more about this structural scan. What have you got for me?!

It's acoustic ultrasound and the device that performs it comes in all shapes and sizes. There's one that can scan the whole wing of a 787 Dreamliner (given how and why it was delayed, due to the shockingly extensive crack it developed during the test flights at the end of its development, where the wing meets the fuselage [*]). As for the science of how this works, I've no idea.

I've only witnessed a handheld small device of this type, used to scan small specimen of CFRP plates before and after various tests in a Materials' Mechanics lab at the local university.

[*] Due to this delay of a year or a year and a half the Dreamliner's nickname was Summer Night's Dream.

:)
 
So, let me see if I got this straight... you went this far just to tell us that carbon fiber isn't a perfect material and as such I should be worried because there's a high risk of the body shell (monocoque) of my Alfa Romeo 4C won't last 20 or 25 years without falling apart?!

I was expecting that kind of argument, not because carbon fiber was used but because it's an Alfa Romeo!

Anyway, here's the reason I was looking for to not want to buy an old Mclaren F1 ever again, I feel much more relieved now, thank you!:D

As for the A380, even though it uses some carbon fiber parts, Airbus will have to excuse me but I won't be flying inside of one if they are planning 1) to land without it's landing gear and 2) expecting withstand an impact force as high as 214g (Highest recorded g-force ever survived - the record belongs to a carbon fiber monocoque with aluminum honeycomb chassis and body, made in 2003 for the IRL IndyCar championship by Dallara Automobili, an italian manufacturer, go figure!)
 
It's incredible how the swedish pilot Kenny Bräck survived this crash, that's what carbon fiber is there for, that and the 695 kg of car weight only (despite the all aluminium 3.5L, N/A V8 Honda engine):

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