I made my first part by resin infusion technique and something went really bad - the gelcoat can be easily peeled off with fingers as you can see in the second picture below.

Complete part: approx 65cm x 10cm


Note that I pigmented the epoxy white just to see how it looks when infused.

Gelcoat peels off:


Note that the fiberglass layer that's below the gelcoat doesn't seem to be completely dry, but it's definitely not white (I would expect to see more white from the pigmented epoxy). I suppose that there isn't enough resin on this side of the part. Also I can separate some individual fibers with a screwdriver and the whole fiberglass surface is rough (I can feel the cloth texture with my fingers). From my experience with hand-layup, the surface that is touching the mold is always smooth even without gelcoat.

Below is a detailed description what I did.

I have the Resin infusion starter kit from Easy Composites and I followed their video tutorial:
https://www.youtube.com/watch?v=VodfQcrXpxc

1) First, I applied the epoxy gelcoat to the mold and I let it cure for a few days.
Some people said that it should be tacky when laying out the fabric, some say that a cured gelcoat works well – for example, this post:
http://www.talkcomposites.com/2278/using-gel-coat-with-resin-infusion#2370
I prefer a cured gelcoat because I have more freedom with laying out the first layer of fabric. Note that I use epoxy gelcoat, not polyester gelcoat, so my gelcoat should be compatible with the epoxy resin I use at point 5)

2) I laid out 6 layers of fabric:
1 layer of 200gsm fiberglass (over the gelcoat)
1 layer of 200gsm Kevlar
4 layers of 200gsm carbon fiber

3) peel ply, mesh, infusion spiral, bag... as in the video. I have put the infusion spiral in the middle of my part.

4) I made the 15-minute vacuum test to make sure the part is sealed. The pressure gauge was constantly showing -29...-30.

5) For infusion, I used a low viscosity epoxy resin (500-900 mPas / 25 C) with a 150-minute pot life. This epoxy resin is specifically recommended for vacuum infusion. I added 5% white pigment (the recommended ratio is max. 10%). The room temperature was around 25 C.

6) The infusion process took a few seconds (I think less than 20 seconds). I was surprised because most people talk about minutes. I think it was fast because the infusion spiral was in the middle of the part, so it only took 5cm to reach the edges.

7) I closed the supply hose and then the other hose as in the video. I let it cure for 24 hours.

Any ideas what went wrong? I will try the same with a different gelcoat - epoxy-compatible polyester gelcoat, but I still have doubts if the part is fully infused.

UPDATE: I have found that I can delaminate the part:

The white is fiberglass, the yellow is Kevlar and black is carbon fiber. It looks like the Kevlar fabric below the carbon fiber layers was not wetted out. I can't separate the carbon fiber layers, but I can separate Kevlar from carbon fiber.

My initial thoughts are waaayyy too dry and quick an infusion,

Slow the infusion down on the resin feed using a line clamp so the resin has time to soak in as it flows.  That should probably solve most of your issues.  I suspect it will fix the gelcoat delamination too .


Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Also make sure that you key (sand) and thoroughly degrease the inside of the gelcoat before laying up your infusion stack .. a fully cured epoxy gelcoat may not create a proper mechanical bond to the infusion resin.

Personally I would lay up my "stack" when the gelcoat is cured just enough to be firm but still have a slight tack to the surface (B-stage) that way it will "stick" the fabrics making it easier to avoid bridging, and the infusion resin will chemically bond to the gelcoat. 




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