Polycarbonate racing car windshield vs aerospace-spec polycarbonate fighter jet canopy - struck by a 20 kg (44 lbs) projectile at 225 kmph (140 mph)



View original post [gfycat.com]




Comments:

8 Dec 2017 01:45 - +2227
I don’t feel this is quite fair, the fighter jet canopy is inherently a more stable, “energy absorbable” shape, versus the windshield being just a....windshield shape...I guess? At least that’s what my gut is telling me. Also, I’m hungry
8 Dec 2017 02:35 - +545
I honestly hate the phrase aerospace spec or aircraft grade. When i get to work in an hour or two im not gonna flick through my design manual and see that as a title, nor am i going to have an option of only one material. Take aluminium, this is one is see 'aircraft grade' used as a selling point on gadgets for sale all the time. If you pay extra for that, you are getting ripped off. We use all types of allys 6000, 2000, and 7000 series very regularly. 5000 series a little less regularly but it still happens. The only difference between my sheet/billet of material to what anyone could pick up from their local metal supplier is that i pay extra and get paperwork that tracks the piece of material from the manufacturer and through the heat treatment process. We then track it onto a job. There is a legislative reason for this, and if there ever was an incident, a) we have proof we used the right stuff and b) if the material turns out to be not what it says it is, we can recall it all. More than 'aerospace spec' polycarbonate not actually existing and being a phrase to just charge more, its actually somewhat offensive to the designer. The aircraft windshield isn't stronger because of a magic material, not to say it isn't different, but design is so much more than that. Others have already pointed out the superior shape, possible dual layer design, and mounting mechanism all play a huge part in its strength. Its also a great deal longer which allows for more deflection. You dont often experience tyres when flying, but you do experience birds. This is something that gets designed and tested for and would have gone through several design iterations. TL;DR: aerospace spec doesn't exist. Aerospace design however, does.
8 Dec 2017 03:03 - +117
Interestingly since this has hit /r/popular, after these tests they decided to go for something completely different called a "Halo". http://i.imgur.com/qpotKp4.jpg Most people hate it.
8 Dec 2017 01:46 - +115
I'd imagine that the 360° mounting of the cockpit poly adds a lot of structural support that the windshield doesn't have. I'm curious how much of the difference is due to the material, and how much is due to the shape, size, thickness, and mounting configuration.
8 Dec 2017 03:05 - +31
I’d like to clarify with this that the racing windshield in this demo is NOT used. The FIA was testing different methods of cockpit protection for F1 and they found that a design called the “halo” could withstand that forces of a tire striking it at 225 kmph and is what will be used in the 2018 season. The design being tested was called the “aero screen”
8 Dec 2017 02:48 - +21
Well an F1 is basically a jet on wheels, so maybe a cockpit wouldn't be a bad idea, ohh wait, until the whole car catches on fire and you can't eject.
8 Dec 2017 01:48 - +20
I'm curious what the difference between, if any, there is between the polycarbonate chemistries/properties. This test isn't nearly as valuable for design data if they are not the same. How can anyone tell if it is the mechanical properties or the geometrical shapes of the windshield/canopy that cause the different reactions? Test one variable at a time.
8 Dec 2017 07:17 - +17
Yeah but what about a 90kg projectile launched 300m?
8 Dec 2017 01:45 - +9
Source: https://www.youtube.com/watch?v=8GSmNuaNGI8
8 Dec 2017 02:12 - +9
Unfortunately fighter jets travel much, much faster than 140mph lol I want to see this at mach 1!
8 Dec 2017 01:42 - +7
Would a bit more windshield for the race car provide the flex needed to not shatter?
8 Dec 2017 06:06 - +6
As someone has pointed out it's not a fair comparison as the racing window is cut off making the internal forces parabolic and essentially tear itself apart
8 Dec 2017 03:39 - +6
Ya, $20,000 or $200,000, take your pick.
8 Dec 2017 08:56 - +5
But does the windshield know why kids love the irresistible taste of Cinnamon Toast Crunch?
8 Dec 2017 08:20 - +3
I'm the only non-engineer on this website, but that fighter jet canopy has some wiggle room, literally. it is huge compared to the car windshield. I wonder if it's so much better or if it's just the increase in real estate that the canopy has to work with
8 Dec 2017 02:37 - +3
I think the fact that the canopy was attached on all sides rather than the open cockpit of the racer windshield made it perform better. Also, the windshield seemed stiffer than the cockpit which flexed & rippled to absorb some of the impact energy.
8 Dec 2017 07:00 - +3
What is the price difference?
8 Dec 2017 06:48 - +2
Why a wheel?
8 Dec 2017 08:25 - +2
Now do the tests again with same-shaped windscreens made of the two different materials. Comparing an arch to a dome isn't an honest comparison.
8 Dec 2017 09:26 - +2
I used to work with a guy who once worked for an aerospace company. Might have been Boeing, but really can't remember. Anyway, he told me a story about how they would test airplane windshields at the time, or more specifically, how they would test them for impacts with birds. They would shoot them out of an air cannon straight at the windshield, like that episode of Mythbuster. Now, I'm sure unlike Mythbusters, they were very exact in everything, including the mass of the bird fired at the windshield. He told me they were using calibrated dead birds. That means somebody, probably in a lab, had to use very precise and expensive equipment to measure the mass of a dead bird. Then you've got the documentation associated with tracking the bird. The really funny part was about the problems they had initially with testing. Their windshields were all failing the bird test and they couldn't figure out why. Every windshield broke. Apparently it took them a while before someone realized maybe they should thaw the frozen birds before they shot them into the windshield.
8 Dec 2017 07:07 - +2
still not enough for my phone screen
8 Dec 2017 05:59 - +2
I want to live in a bubble made from aerospace-spec polycarbonate.
8 Dec 2017 09:08 - +2
IF anybody ever finds a way to dissipate (kinetic) energy instantaneously in; sports helmets/padding, vehicles, military armor, planetary bodies, etc. . . . A personal shield that transmits the kinetic energy . . . elsewhere?! That's a Quintilian Dollar Idea. Force-Field + Dissipation! No more face-plants, no more concussions, no more trauma. Bubble-People. #Kineticenergyisakiller
8 Dec 2017 04:45 - +2
That’s how goose went
8 Dec 2017 03:40 - +1
If the windshield was as large as the canopy I think it would have been able to flex enough to also absorb the impact without breaking.
8 Dec 2017 04:12 - +1
That's all fine and good, but how would it handle a 90kg projectile that has been launched 300m? *That's what I thought!*
8 Dec 2017 02:51 - +1
The post mentions the speed but would it be the force or the momentum that deforms/breaks the window?
8 Dec 2017 03:49 - +1
What is this new tire-launching weapon?
8 Dec 2017 02:57 - +1
That looks like an F-16 canopy. It is more than an inch thick, and weighs about 250 pounds. There’s a trade off for protection.
8 Dec 2017 02:27 - +1
What's the fluff?
8 Dec 2017 03:03 - +1
Wibbly wobbly spacey wacey
8 Dec 2017 03:47 - +1
What are the price differences though?
8 Dec 2017 03:11 - +1
Anyone else skip over pretty much all the words and numbers in the title..?
8 Dec 2017 03:52 - +1
The tire kind of hits it at a bad angle where it just skips right over the top of it.
8 Dec 2017 03:33 - +1
does the front usually fall off?

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