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!

*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.

Jobs

Chopped fiber composite analysis

Chopped fiber composite analysis

(OP)
I was curious if there was a simple way to analyse a chopped fiber random orientation composite.  Can it be analysed nearly correct as an isotropic material? Idea being to make a with a chopped carbon epoxy paste and squeeze it into a mold.

RE: Chopped fiber composite analysis

The flow of the material in the mold will partially align the fibers in the direction of flow and along the mold surfaces; so the material will likely not be purely isotropic.  You could possibly use properties from specimens loaded transverse to the flow direction in a plate to give approximate conservative values.
 

RE: Chopped fiber composite analysis

(OP)
Maybe instead of squeezing into a mold it could be packed into two halves of a mold and then joined together to preserve the randomness..? If it was very random could it be considered as isotropic and give a close estimate?  Also is there any known materials properties for chopped carbon epoxy like this or would I have to test it?  Thank you for the insight.

RE: Chopped fiber composite analysis

(OP)
Im having trouble understanding why only 2 planes.  If you find the data I would really be grateful.

RE: Chopped fiber composite analysis

When the mould closes it will flatten the fibresout so they tend toward being parallel to the surface, so with originally random orientation, as you close the mould you will not disrupt the random orientation perpendicular to the mould closing, but you will disrupt it in the direction the mould closes.

Come to think of it, say you where moulding a bucket shape, you would not disrupt the orientation across the bottom in any way but the thickness direction, but the sides would be oriented a bit in line of draw as the core pushed into the cavity.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
http://eng-tips.com/market.cfm
for site rules
 

RE: Chopped fiber composite analysis

For material properties, the material supplier should have some sort of representative data (likely on the optimistic side).  Data sheets should be available on the web, or you could contact the vendors.

SW
 

RE: Chopped fiber composite analysis

(OP)
The material I was going to use was chopped fiber held together in thin flakes if that changes anything...

RE: Chopped fiber composite analysis

(OP)
From the sound of it it seems like the fibers/flakes align in the direction of flow as the molds are assembled.  Is that true?

RE: Chopped fiber composite analysis

More or less.  The amount/extent of alignment is highly dependent on the particular material, part shape, mold details and injection parameters.  If you have not worked with this type of material before, I highly suggest talking to a technical rep from one of the material suppliers and also to a mold designer. There are some analysis codes (Moldflow, etc) which can predict alignment, but of course you need to supply the material properites, part and mold geometries, etc.

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


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close