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Bullet-resistant glasses
2

Bullet-resistant glasses

Bullet-resistant glasses

(OP)
How military aircraft (glass) windscreens provide protection against bullets or impacts from flying birds?

RE: Bullet-resistant glasses

really thick is part of it

RE: Bullet-resistant glasses

The material used has fracture toughness in excess of the stress intensity applied during loading.

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: Bullet-resistant glasses

Just for the record, they do NOT fire frozen chickens at canopies.  They use a big compressed air gun to fire *thawed* frozen chickens at something like 300+ MPH.

Takes a while to clean up afterwards.<g>

RE: Bullet-resistant glasses

I think they did use frozen chickens once, not knowing any better and the canopy did not fare too well.  Then the line directing defrosting the chickens was added to the procedure!  Maybe this is an urban legend, but with my experience in the Navy and as a Government contractor, it's really believable

Blacksmith

RE: Bullet-resistant glasses

The material usually isn't glass, but a polymer.

And they still shoot chickens out of cannons at jet engines to test bird ingestions.

RE: Bullet-resistant glasses

Yes, and they use walnut shells to clean deposits of the blades and vanes.  Let's see, walnut chicken.  I'm getting hungry!

RE: Bullet-resistant glasses

(OP)
I thought that several layers of glass interleaved with layers of vinyl, then bonded together, served to make windscreens capable of withstanding the impact of a large bird when plane velocities reach up to 400 mph. Has this practice been superseded ?

RE: Bullet-resistant glasses

25362,

Safety glass has been used for numerous applications like canopies.  Safety glass uses glass layers separated by polyvinyl butyral.  However, monolithic polymers like polycarbonate also are used for these applications.

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RE: Bullet-resistant glasses

You are refering too transparent armor, which consists of polycarbinate laminates.  Polycarbonate is a plastic material 30 times stronger than acrylic which is 17 times stronger than an equal thickness of single strength glass. Usually glass-clad polycarbonate products are a multi-ply composite laminate combining polycarbonate and glass using special  polyurethane high adhesion bonding layers.  The outer layer has a wear glass layer and inner layers are spall resistant.  Made by companies like Simula, Inc or PPG.

RE: Bullet-resistant glasses

I have heard that a certain MIG canopy is up to 4 inches thick polycarbonate.  Don't know if there is any truth to it.  

RE: Bullet-resistant glasses

Thichness of two to four inches are common.

RE: Bullet-resistant glasses

Thanks for the reminder
I just bought a piece of “bullet proof” material from:

Kel-Tech Plastics Inc
(253) 472-9654 3510 S Pine St
Tacoma, WA
1-800-KEL-TECH
www.keltechplastic.com

They said they would be happy to answer questions.  

Tom

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