Talk Composites - The Forum for Advanced Composites

Brittle thickened resin

http://www.talkcomposites.com/Topic31381.aspx

By oberflaeche - 12/24/2018 9:23:09 AM

Hi
I made a carbon front fender for my Husqvarna 701 Supermoto in a four part mould. The part of the mold that depicts the assembly area is cast from polyurethane.
 
I fill the mounting area of the front fender with a thickened resin before vacuuming.
I use about ¾ teaspoon chopped carbon fibre strands on 65 g of resin.

The result looks neat, but the assembly area is more brittle than I expected.
It sometimes breaks when I drill it. I am afraid it will break in rough use.
If possible, I do not want to build a new mould.
Any suggestions?
Regards
Frank
By oberflaeche - 1/9/2019 7:58:16 AM

 
Frank - 12/26/2018 12:32:43 PM
@Hanaldo:
With the next Part I will try to degas the resin-chopped-strand-mix.
@ George Sychrovsky :
Yes, it would be the best way, to build a new mould and to design the mould for parts made of reinforced resin.
But the mould is already made the way it is. And I already produced a useable Part in it. So, the job is done and the bike has its Carbon-Front-Fender made of CF looking nice.
I do not want to build a complete new mould.
Perhaps I can change the mould-part that is made from polyurethane.
1) I probably can design it to leave a flat area in the mounting-section of the Front-fender, to which I can bond an angle and the tubes made of CF.
2) Another way would probably be, to drill a hole in the PU-Mouldpart, pull the Vacuum through this hole and feed the resin from both small ends of the mould.
@oekmont:
Next time I will try to bring more reinforcement into the mounting-section and degas it.
@f1rob:
I agree to this. I just copied the part. Perhaps option 2) can help with that.
I have to think about it.
Regards
Frank

For the last front fender, I did not fill the mounting area with chopped carbon fibre thickened resin as usual, but rather with dry carbon fabric. Just as the rest of the mold in the vacuum injection process. With a decent result. The mounting area was completely infused with resin during the infusion and is now just as stable as the rest of the component.
Picture will follow...
here it is:

Regards
Frank