Damaged carbon fiber retention sleeves

[UKpete]

We have some permanent magnet alternator rotors (with carbon fiber sleeves) that have been removed and subsequently damaged. The damage appears very slight - mostly a single small dent perhaps 1 or 2mm across and a fraction of a mm deep, with no loose fibres evident under an eyeglass. The rotors spin at approximately 50krpm, with a max operating temperature of around 150°C (300°F).

I understand that they are wound to about 3mm thick with a very high pre-tension, have a PEEK matrix and are ground on the outer surface (I don't know why; the finish is very smooth though). Rotor size is approx 50mm o/d and 150mm long.

The question is - do we scrap them? They cost about $1000 each, but if they fail they trash the whole alternator: $3500. Can they be repaired?

I have a couple of digital photos but no web-site to post them on.

Any opinions would be much appreciated.

 

What is the wall thickness?

The part was probably wound, meaning the fibers are pulled in tension around the ID mandral. Also Peek is a very tough resin. In my PEEK/Carbon composites the Izod impact is 13.3 ft lb/in. So depending on how the damage was created there may not be any significant structural impact depending on the wall thickness.

RMDavies@americanmatrixcorp.com

http://www.americanmatrixcorp.com

 

[UKpete]

Thanks for your reply.

The wall thickness is approx 3.0mm, so the damage is relatively very shallow. My main concern is that inevitably some fibres will be broken and they may start to peel. Of course on the surface there will be discontinuous fibres anyway as it is finish ground (still a bit puzzled about the necessity/wisdom of this).

I am also reassured by your comment that Peek is tough. If we had a proper overspeed rig I suppose we could run the rotors (hot) at overspeed to see if any fibres move.