Ballistic containment


My interest is in the subject of light hovercraft. Recently the subject of guarding of thrust propellers has become important.

Most hovercraft use axial fans or propellers to provide thrust, and these are normally contained within a guard or duct. There is the need to be able to show that a particular guard construction is capable of containing a failed blade of known kinetic energy.

Guards are usually constructed of GRP or wire mesh, and are sometimes reinforced with kevlar. Typical blade kinetic energies are in the region of 2000J - 3000J.

Since many craft, and therefore guards, are one-offs built by amateurs, there is the need to provide a means to calculate, or otherwise verify, the capability of a guard to contain the given KE. This appears to be somewhat of a problem!

Can anyone suggest any means to verify guard capability without resorting to potentially expensive ballistic testing?

References to prior work, calculation methods?

Or references to ballistic containment materials that can be supplied with proven performance to contain 'x' J from which a guard may be constructed?

Regards Ian

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Ian wrote in news:1$

One approach would be to work out the work involved in a fully plastic, hinged, deformation, of the guard. In theory, because it uses an assumed mechanism, it provides an upper bound to the energy absorbed, but by using a parametric model, and differentiating, you should be able to find a reasonable limit.

Given the popularity of this field, perhaps it would be better to define an overstrength solution and make that the legal minimum.


Greg Locock

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Greg Locock

"Ian" wrote

Dig up some textbooks on jet engine design; jets have a requirement to contain pieces released during a rotor burst. This is basically the same requirment as what you're talking about, just with higher energy. You can also reasearch the Federal Aviation Regulations (FAR's) on engine containment.

Any of the companies that make ballistic armour for the police or armored vehicles should be able to provide this kind of data. I'd start be going to body armour manufacturers and work your way up the chain from there.

Good luck! Tom.

Reply to
Tom Sanderson

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