I popped my first ever composite part out of the mold yesterday and was thrilled with the results. The surface is flawless!

The only problem I'd like to work on for the next part out of the mold is the disruption in the weave around the edges of the soric core. Any way to protect the weave? Add a layer of veil or something between the soric and the surface layers?

Layup was 2 layers of stabilized 200gsm 2x2 twill, soric core (the rectangular cutouts were in case I had to really pull hard to get this thing out of the mold, turns out I didn't at all), then two more layers of carbon. After that was peel ply, flow media, vac bag. I used the MTI hose and MTI valves and I think based on the surface finish on both sides I have the resin part pretty nailed?

2 layers carbon + soric, 2 more layers of carbon after this. Cutouts were to add shear strength in case I had to really yank to get it out of the mold.


Infusion happening.



Here's the soric edge print through on the face of the part that I'm wanting to eliminate.  The surface is perfect, just a shift in the weave that you can see.


One more angle of the issue:


Backside looks great to me but, again, not a lot of experience to go on here.


Couldn't be happier in the end for my first part, just always looking to improve!
Step one in my mind is to eliminate the cutouts in the core but there will still be the issue at the edge of the core, I don't want to wrap the core up the corners.

Thanks,
Alex

The problem is the thickness difference between the Soric and the surrounding laminate is essentially bridging, and then that higher volume of resin shrinks more and creates the shrinkage. The only way to avoid it (without making the skin on the mould side of the core much thicker) is either to chamfer the edges of the core so that it tapers off and is flatter where it meets the laminate, or to build up the thickness of the laminate using 2" strips or tape around the Soric. If you're using 2mm Soric then you'll need 8 layers of a 200g woven tape or fabric to soften the edge of the Soric.

Obviously chamfering the edge of Soric isn't easy due to the small cells and the polyester webbing just tears, so that technique is more suited to solid foams like Divinycell. But it can still work with Soric, just takes a bit more time and care.


Surface finish looks great, so looks like everything else went well! MTI hose is a great product when learning the infusion process. Never had a lot of success with the valves myself, they never ever seemed to cut off flow. I know they can get stuck open sometimes, but I've used them 10 or 15 times and I always end up clamping it before the valves do anything, even if I leave it well past the point where I would normally clamp it! 

Hanaldo is spot on.  You could use subsequently smaller width pieces of tape to in effect taper the tape as well.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Awesome, thanks guys!  That's a pretty easy solution, I'll do it on part #2 next week.

MTI valves worked really well for me on this part, they cut off completely about 75% of the resin I calculated I might use.  I've meant to weight the part to see how I did on ratio but haven't  done the math yet.

Thanks,
Alex

If the cutouts aren't necessary, I would say the easiest and lightest solution will be to extend the core to the corners if the part (into the 90° edges). By doing this, you avoid the whole problem. I do this every time when possible.

+x

 

oekmont - 4/10/2018 9:14:22 AM

If the cutouts aren't necessary, I would say the easiest and lightest solution will be to extend the core to the corners if the part (into the 90° edges). By doing this, you avoid the whole problem. I do this every time when possible.

I wondered about this but was worried that the bridging potential at the edge of the soric would line up with the sensitive area for bridging in my already too sharp corners and aggravate that area.   Anything special I would need to do I the sharp corners? Run it all the way up the side a bit maybe? 

Thanks,
Alex

No, just into the corner. You want the end of the core to align with the already existing visual cut, the edge of your rectangles.

As long as you can get the fabric into all the corners and recesses in the mould, then no reason why you can't use a thicker fabric in that way. It is usually a much better value way and quicker way to make thicker panels.


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant