Composite Usage in 400 F Environment? 2

[Stringmaker]

I'm interested in exploring the possibility of using composites within an aircraft engine environment - particularly for the rotor support structure. The forward parts of the engine are confined to temperatures of 400 degrees F or less. The environment would be an air-oil environment. Aircraft engine oil can be hygroscopic. I'm no pro on composites and am wondering is there any potential for use here? Primary concerns for structural integrity are HCF and Strength - in particular fan stage blade loss.

Any thoughts would be appreciated.

Regards.

 

[Compositepro]

Bismaleimide (BMI) resin composites have become the material of choice for that type of application because of their strength and temperature resistance as well as reasonable cost.

They are available as high flow liquid infusion resins, prepregs and compression molding compounds. BMI's have been used to make the air/oil seals in G.E. jet engines for decades as well as inner cowlings, air ducts, and thrust reverser cascades (louvers).

 

[RPstress]

As Compositepro says, BMI is a good choice for this sort of service temperature (180-230 deg C). The resins are reasonably tough. One example we've used successfully is Hexcel's 5250-4, which is also available as 5250-4 RTM. You're a bit limited if you need a film adhesive, though.

BMIs are about as good as good epoxy when it comes to the chemical environment, so reasonably resistant to fuel, oil, solvents, etc.

Most cyanate esters will also take this sort of temperature, but they tend to be more specialised and expensive. (They have very low out-gassing and are often used for satellite structures.)

The new benzoxazine resins also make some claims which make them look tempting, but in my opinion they've a way to go before being regarded as proven. They might well be worth bringing in to any material selection studies done.

Polyimides are really for higher temperatures than this.

There is quite a bit of composite in modern aeroengines these days. If it's stators or OGVs then leading edges need erosion protection (often PU or similar is enough, but thin metal plating or a sheet metal wrap mey be needed).

Carbon/BMI will generally behave well in HCF compared with metal. You need to keep an eye on formation of interlaminar cracks.

Static strength-wise think aluminium-ish. (But 55% of the density, of course.)

For more specific details there are of course many papers and it's worth a few hours googling. (Not entirely sure exactly what your "rotor support structure" is, I confess.)

 

[Stringmaker]

Thank you for the informative posts gentlemen!

 

[rodneybennet]

With regard to high temperature composite solutions you may also want to look at

http://www.composite-agency.com/materials-forum.htm

Their integrated chemical-physical approach for material selection can be helpful.

Rodney