Talk Composites - The Forum for Advanced Composites

hood problem

http://www.talkcomposites.com/Topic36932.aspx

By beliblisk - 6/3/2020 7:49:03 PM



Hi guys.

I ran into a bit of a problem today.

So i made e46 m3 hood. All good except for a little bulge (located in middle kevlar/cf "island on the right side o)n the top side (that i didnt notice untill todat when i took glued item from top mould) :/

After mild postcure (sun so max 50*C atm) it came out great so somwhere from that point to prior of bonding halves together this happend (inbetween i was only cutting vent holes).

Stack was as followed (top part) :
-245 2x2 cf
-600 2x2 cf
-200 cf/kevlar

All this time (apart from cutting & triming) paet was laying flat in mould to awoid any accidental damage in workshop. 

Halves arenow bonded and i can not seperate them again.

I was thinking of heating it gently locally with heat gun and then put so soft weight on and let it cool of (as atm TG is quite low...... plan was to let it full post cure bolted on the car and then sand it and get it clear coated). 

Any ideas how this happened and any alternative ways to solve it?

Thanks a lot
By Steve Broad - 6/10/2020 2:08:04 PM

 
oekmont - 6/10/2020 12:28:15 PM
You are talking about regular twill, or am I wrong? 0° or 90° should not be a significant difference.

It was nothing to do with the twill. it was the number of layers at the joints. Where the strips overlapped there was an extra layer. If I overlaid the two layers at the same place there would be 4 layers instead of 2, making a stiffer strip. However, I decided to rotate the second layer so I had strips of 3 layers 250mm apart forming squares as opposed to strips of 4 layers 250mm apart running in one direction only. Does that make sense? :-) I have no idea which method would be stiffer, but the difference would be marginal.