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9/22/2017 12:11:25 AM
Posted: 2/3/2006 8:50:40 PM EDT
I was just pondering some of the possible future advances of the AR system and it oocuried to me I don't know of one company that offers a light weight FF RAS made of composites.

I mean they are strong enough for most modern hand gun lowers, why not a RAS????

I figure a compositie AR lower, gas piston upper with composite RAS and regular upper reciever, sights and M4 stock are the future of the AR. Now if someone would mass produce one....

What says the hive mind. Are Composite FF rail systems possible? Economical? Worth the weight?
Link Posted: 2/3/2006 11:12:24 PM EDT
carbon fiber is only non metallic ive seen. heat factor maybe?
only nonmetallic parts on my ar are the pistol grip and buffer end cap. i kinda like that.
Link Posted: 2/4/2006 12:26:53 AM EDT
Composite do not fair well with compression load, the fiber are not being stressed, and the epoxy matrix is relatively soft, so the actual rail will creep under load, and your accessory will eventually got loose and fall off or the barrrel nut will eventually come loose. That is the reason why most composite rail system uses metal rail and barrel nut.

Other than that, most fiberglass, garphite, and.or kevlar based composite should be able to withstand the heat generated by an AR, basically use a high temp epoxy as the matrix will work.

The typical FF rail I saw is what the aero industry called "black aluminum", which basically replace the metal with carbon composite, gain some weight advantage, but not utilizing the most out of the material. To gain maximum strength and mechanical stiffness off a tube, the best way to make the tube is filiment or tape wounding, and the worse way is to use chopped strand fiber. If holes are needed, it is best formed during wounding, because drilling holes will result in broken fiber, thus loosing strength an d stiffness.

One dis-advantage of composite is the thermal conductivity is lower than aluminum, so the weapon will cool down faster.

Filiment or tape wound tubes are expensive to manufacturer, but one can purahcsed already wound tubes from Mac-Master Carr, and bound in and shear tie the require metallic components.

Be very careful of mixing aluminum with graphite. They will generate galvinatic reaction, and the graphite will corrode away. I seen numerious products that mixes aluminum with graphite, and sometimes I wonder if those people know what they are doing. Best material to use around carbon is steel or stainless steel.
Link Posted: 2/4/2006 2:54:56 AM EDT
One way of doing it is to include metal inserts in the layup where the rail goes, and machine it after the part has cured. Aluminum would be a poor choice because carbon fiber makes aluminum corrode at an accelerated rate but Titanim would be great.

I've put aluminum parts in my layups before but they were all clear anodized and thus sealed off from the corrosive effects of the epoxies.

Dave
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