Ann, you raise the issue of crash-optimized composites. That got me thinking, how safe is a vehicle if it's designed with this lighter weight material? Beyond safety, what about maintenance costs given that most vehicles are involved in some sort of minor fender bender if not a full-blown accident over the course of their lifetime. Is it much more difficult to repair a composite structure vs. steel door panels, for example?
If correctly done lighter composite bodies can be a lot safer than steel ones.
Take the F1 racecar whiich can hit a wall at 200mph a yr or 2 ago and she walked away from it because of the composite tub/frame plus other energy absorbing features using tires, suspension, structures, etc.
My vehicle designs use the same tech plus more and can easily out perform steel for safety.
As for repairs in composites is fairly easy. In many cases you just soak the break in epoxy, let cure and grind of anything that doesn't look like a car ;^P. Then finsh sanding, paint. Bigger just buy a replacement part and have it installed. Not hard though different from steel. Most bodymen already have composite experience in finishing that should help them with fibers. There are many boat/FG shops that can do it too. Even better it's rather easy to do yourself saving much money.
As for the new material it doesn't sound that useful as other things like foam, plastics are lighter, more cost effective. Kind of depends on it's cost.
And generally to cut weight, thus cost, one want more stiff fibers/components, not less as we already have less stiff ones that cost less.
Thanks for your comments, Jerry. While there are marine shops and hobbyists versed in composite finishing, I would think there will eventually need to be a wholesale retraining of body shops and automotive maintenance suppliers (even at dealerships) to keep up with demand for repairs on composite-based vehicles as the use of these materials become more widespread. As for my safety concerns, your comments about the durability and structural integrity of fiber-enforced composites are a comfort. It's surprising to me, but definitely a comfort.
Jerry, I'm wondering what the F=ma situation is when a composite car hits a steel-cage vehicle. So in other words, do we have a situation like today, where people want SUVs because they don't want to be in a small car that's hit by an SUV? (They want to be in an SUV.) When every car is composite, it'll be an equal "battle," for want of a better phrase. But when there are some composites mixed in with a legacy fleet of steel cars, what are the crash dynamics?
@Ann: I think you mean "endure static distortion of up to 240° without damage," not "endure static distortion of up to 240°C without damage." Thankfully, angles are not measured in Celsius or Fahrenheit; 1° is just 1/360 of a full rotation - no matter what country you are in! For a 15% glass filled nylon injection molding compound to be able to withstand this much twisting without breaking is pretty incredible.
@Jerry: The point is not that the material is less stiff. According to the press release, it's actually more stiff than comparable injection molding compounds - in other words, if you apply the same amount of torque, it will twist less than other compounds. However, unlike other materials, if you keep putting torque into it, it won't break. It's stronger and/or more ductile. Since the press release doesn't say how much of the twist is recoverable, it's not possible to determine which. It would be interesting to have a third photo showing how much it untwists when it is unloaded.
According to the press release, it took 35 N·m of torque (about 26 ft·lbs) to twist the test specimen 240°, but since the dimensions of the test specimen are not given, it's impossible to translate this into units of stress, which would be more useful.
It's also not quite clear from the press release what the benefits of the unusually-shaped test specimen are. (And there are some real disadvantages to doing your testing on a non-standard test specimen - you can't compare your results to anyone else's!)
Still, this does appear to be a significant advance in injection molding compounds. It would be good to see datasheets for these grades. Here is a datasheet for Ultramid B3WG6 CR, which was BASF's first crash-resistant nylon formulation. The tensile modulus, tensile strain at break, and impact strength are all quite high, compared to "plain vanilla" 30% glass filled nylon-6.
By the way, many people would not think of this type of material as a composite, even though that's exactly what it is. Since it's made by injection molding, most people would just consider this to be a plastic.
The steel industry has been fighting the growing use of composites. The most recent argument has been around the entire lifecycle (materials, use, recycling) emissions of steel versus composites. When it comes to crash optimization, steel may lose the argument.
Thanks, Dave, the addition of "C" was a copyediting error. Yes, I was talking about angles, not temperature.
And that was a good summary of the benefits of the material and the relationship between torsion and strength/stiffness. This material is specifically targeted toward items such as steering wheel components, body inserts and seat structures, as noted in the photo caption. In other words, items that need to withstand a crash without breaking, and "bounce back."
Much depends on how it is designed. My style is soft ends and extremely hard cabin shell with 4 point seat belts in a safety designed seat like racecars do. I have other things that are likely patentable that cut forces by 50-75% on top of F1 style above.
I build a frame/rollcage of composite bars between the skins along with kevlar type cloth as the most inside layer keeping any breakage together and spread loads.
Now when hit instead of crushing it's going to get knocked around but I'm good with that, already having one accident that totaled the compact car that hit my composite one and mine only needed $40 in materials to put back on the road.
One good thing about low mass is you can only put as much force on it as it weighs. Anymore than that it just squirts away.
As for SUV's it takes those into account. I expect that the safety will be overall as good as the better, if not best cars. And in the same size of vehicle, Composites would win easily. My new vehicles are only 500 and 1300lbs.
It's not like this is new as it's rather old hat in raceboats, aircraft and racecars for 4 decades now.
There is a vid of an Audi 100 hitting a composite car called the City head on and the Audi lost is another example. Can't remember the name of the German composite company who made a bunch of prototype composite cars that set a bunch of records.
Once I'm in production I'll crash some but have to make some money before I can afford that.
Maybe this is obvious to the mechanical and material engineers out there, but when you are talking about optimization and distortion does that mean that the materials return to their original shape after the distortion or does it just mean that the don't have a catastrophic failure. I'm trying to get a perspective as to whether this is an improvement on some of the current designs that are "safe" but you end up totaling your vehicle after a minor collision
@Jack: Actually, it's not obvious at all. Neither the story nor the press release indicate how much of the distortion is actually recoverable. That's why a third photo (showing how much the test specimen un-twists when the load is removed) would be so helpful.
As you point out, materials which permanently deform under low loads would be undesirable. That being said, materials which have the ability to bend rather than breaking can absorb a lot more impact energy than materials which simply break when they are overloaded. If I were in an accident, I would much rather that the energy of the collision be absorbed by a piece of plastic or metal than that it be absorbed by my body. After all, if I live to see another day, I can always fix my car later!
We want materials which are both strong (require high loads to permanently deform) and tough (can absorb a lot of energy without breaking). It looks like this latest batch of Ultramid nylons fits that bill, at least as far as injection molding compounds go.
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