×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Damaged carbon fiber retention sleeves

Damaged carbon fiber retention sleeves

Damaged carbon fiber retention sleeves

(OP)
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.

RE: Damaged carbon fiber retention sleeves

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
www.americanmatrixcorp.com

RE: Damaged carbon fiber retention sleeves

(OP)
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.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources