×
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

Composite Aircraft Structure

Composite Aircraft Structure

Composite Aircraft Structure

(OP)
Analyzing repairs to metallic aircraft structure by reverse engineering applied loads,having material allowables,and knowing failure modes is a routine action performed by non-OEM engineers in the industry.

Analyzing composite structure is a different animal all together. Material 'A' & 'B' allowables are hard to find / non existant, applied loads by reverse engineering joints is difficult / impossible with out lots of testing, and laminate failure modes are difficult due to unknown applied loads.

So my question. For those of you out there who have anlayzed composite repairs on aircraft structure what process did you follow, where did you find allowables, and have you applied it to primary structure?

With the 787 / A350 coming, is there going to be anybody capable of analyzing repairs other then Boeing/Airbus? Will this then make airline, MRO, or other engineers essentially into total paper pushers?

Any thoughts are welcome.

Regards,
MNLiaison

RE: Composite Aircraft Structure

I attended a course by Alteon Training in Seattle called  "Composite Repair Repair of Advanced Composite Structures For Engineers" not too long ago.

http://www.alteontraining.com/training/coursedetails.aspx?id=1948

The same question posed to the instructor.  The answer was that a lot of the composite material properties are proprietary and not available to aircraft engineers.  

There are checks that an outside engineer (not working for an OEM) can do such as the thickness x stiffness (production) must be equal or greater than the thickness x stiffness (repair).

The Alteon course offers guidance how to accomplish these calculations.  But the reality is that we outside aircraft engineers have to reply on the OEM’s to provide repair approvals.

I wished they taught paper pushing in college.


RE: Composite Aircraft Structure

MN Liaison
Your comment” Analyzing composite structure is a different animal all together. Material 'A' & 'B' allowables are hard to find / non existent, applied loads by reverse engineering joints is difficult / impossible with out lots of testing, and laminate failure modes are difficult due to unknown applied loads."
This has always been a problem when repairing advanced composites. Early on when most advanced composites were fiberglass reinforced plastic. It was sufficient to design for rigidity; you knew that if the laminate was stiff enough it was more than strong enough.
  With the greater stiffness of carbon this is no longer the case. The other wild card in this equation is the bond line on the repair. You are always doing an adhesive joint; you are adding new material to an existing structure, very often in conditions where you cannot match the methods used to produce the factory part. Example Vacuum lay-up with heat blankets on a part that was autoclaved. You may not be able to debulk to the same extent that the factory did with the result that your resin ratios may be higher than the original part. Peel strength at the bond line is also critical. Not all resins that are good for laminating have high peel strengths. On some repairs it may be better to accept a resin with a lower structural strength and higher bond line/peel strength.
   In some cases you may have to do test coupons before you do the actual repair to check your analysis .
B.E.

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