GLARE composites 3

[gontek]

Can anyone share specific construction techniques using GLARE composite, such as aluminum thickness, epoxy type, glass type, radius limitations, or something else I am not thinking of?

If someone were to design a new plans-built type aircraft using state of the art materials now, like GLARE, what factors might prevent or hinder someone from working up a GLARE composite structure in their garage workshop?

 

[berkshire]

gontek
One factor hindering, but not preventing, a fiber metal layup as a home built project, is the proper preparation of the metal parts of the layup. Aluminum is notorious for debonding at a later date from epoxy resin unless the surface preparation is meticulous.
Having the metal parts professionally cleaned and pre-coated may be a way around this limitation.
B.E.

 

[rb1957]

i would have thought that the cost would have made it prohibitive for a home-built ?

i know that de havilland in toronto did a bunch of research on glare, including forming sheet into stringers. whilst they probably won't be too helpful (commercial secret) i'd've thought that aloca (or whoever makes/sells the stuff) would be intereted in helping you.

i believe it comes in 0.012" thk 2024 (or 7075) sheets with 0.008" thk glass fiber (so that a 2-1 sheet is 0.032" thick, and a 3-2 is 0.52" , ...).

why are you looking at this "exotic" material over plain sheet ?

good luck

 

[berkshire]

I believe Douglas now Boeing Did some work on the C17. Quote, "Glare Has also been used in manufacturing of latest models of C-17, cargo door." With this material. It would be interesting to find out if they did anything other than just substitute it for conventional aluminum sheet.
B.E.

 

[gontek]

I'd consider using GLARE instead of foam/fiberglass sandwich composite, I think if done right a GLARE airframe could be lighter than foam composites, and I imagine a combination of metalworking and fiberglass-epoxy construction methods, if well thought out, could yield a faster build time. The benefits of fiber composites over traditional aluminum rib-skin are strength vs weight. From what I have read GLARE improves the strength to weight from foam composite, although I could be misled.

I just recently watched the old "The Rutan Composites" videotape starring Burt Rutan and Mike Melvill, from back in the 70's, and it occurred to me that leaps in the application of state of the art aviation technology happen in the garage, not at Boeing or Cessna. Not having worked with it before, I wanted to seek some opinion from those of you who have more experience hands on with GLARE. thanks for your input.

 

[rb1957]

it may be structurally for efficient, but investigate the cost (i think that'll put you off it !)

 

[berkshire]

gontek
The Rutan Composites video, was made by them ,after watching the methods and techniques used by Manfred "Fred" Jiran at a sailplane repair shop on the same field, (Mojave airport) and realising that these same methods could be used to fabricate an aircraft as well as repair it.
B.E.

 

[gontek]

Interesting, Berkshire. I did not know that.

I attended an EAA meeting last night, there are quite a few builders in the area, mostly Vans, some Pitts, a Cozy, and a Sonex. I also discovered I can have access to a CNC water jet, or soon a laser, for next to nothing other than materials - so that is nice.

RB - that sounds like really thin aluminum. The thinnest I have found without really trying too hard is 0.016 2024T3 ALCLAD. Yeah it's expensive but a lot of people are using it. Maybe I can just glue together some recycled beer cans :>

 

[rb1957]

once it bonded together it's alot stiffer than 0.032" sheet ... 0.016' sheet needs carefull handling (as you'd expect)

 

[gontek]

Uh, anyone know if you need an autoclave?

 

[rb1957]

no ... you buy it bonded from aloca. now if you had access to an autoclave, you could Possibly make your own ... the raw materials are easy enough to come by, glueing them together would be the trick.

 

[gontek]

Yeah, that's what I was going for, making my own. I think the beer can thing might not be a bad idea, not for an airplane, but for me to experiment on my own with small sample sizes. I'll see how that goes and maybe I'll make a model plane or a canoe if it goes well. thanks

http://www.scielo.br/scielo.php?pid=S1516-14392006000300002&script=sci_arttext

 

[gontek]

One more thought I have had concerning GLARE - there is little difference in the construction of GLARE material and a capacitor other than one is used structurally, and the other is used to store a charge in the form of electrical energy.

Could static electricity build up on the outer shell of aluminum until the voltage is sufficient to pass through the dielectric (fiberglass/epoxy) when I touch the wall from the interior of the plane? Of course a faraday cage protects the interior of an aero structure, but ....

I'll end with the ever prevalent aerospace engineering question:

What if...?

 

[rb1957]

it may depend on how you're going to attach your "glare" to the structure, assuming you have frames. the rivets probably provide enough of an electrical path. you could use a metal mesh ply, you could see what airbus do for this concern (on the 380).

 

[berkshire]

gontek (Aerospace)
I work with Aluminum composite panels in a non aerospace application. When moving and working on these panels the static discharges, especially in dry weather can generate a spark sometimes an inch long in air.
Not to mention shocking the mover.
B.E.

 

[Andries]

Hi gontek,

GLARE, an aluminum / fiberglass sandwich, was invented at the Technical University of Delft in the Netherlands and it is now commercially supplied by Alcoa (I think). I may have some info on bending radii which I will post if I find it. GLARE is quite expensive however.
Try TU Delft website for papers on GLARE.
It is used on the new Airbus A380.

Regards

Andries

 

[Stache]

Many years ago I work on a project for the new elevators installed on the F-111 aircraft using metal to composite lay up. Needless to say this was a manufacturing nightmare and many articles were rejected because of the lay up and contamination. However being the government we had lots of money to make it work despite our failures.

We used 0.010 thick aluminum formed using graphite as a lubricant between the dies to keep a uniform thickness while maintaining a constant temperature of the skins. After about a year of trail and error we got it right with the bond line. The next major problem was the auto clave and holding the part in place under vacuum while it cured.

Yes, the project did work, but we wasted a lot of money and man-hours working out the problems. I just can’t see how this process would be manageable for an experimental homebuilder with out the vast support of a clean room, chemicals, and auto clave to name a few to make it work. We also had a problem with the use of rivets damaging the bond lines by shop personnel with no experience with the new materials.

Having work with composites I know the importance of constant temperature, moisture levels and process specification that must be followed every time to make it work.

I know the GLARE materials are on several aircraft now flying and it works well, but I have to caution home builders on this one. I might suggest you contact your local FAA office and request assistance before you build something that may never be signed off even as an experimental.

 

[berkshire]

Another item to consider using GLARE.
This quote is from Design News:
"As with any material, however, there are always trade-offs. And in GLARE's case, it involves a loss of stiffness. The material has a flexural modulus that's 5 to 6 percent lower than a comparable aluminum sheet. That stiffness hit isn't a big deal within an individual structure, but it can shift loads to other parts of the airframe. "When you reduce the modulus of one structure, you often put a burden on other structures,"

This was the problem encountered when designing fiberglass composite aircraft. Designers had to add more glass than they needed to get the stiffness.
B.E.