First carbon parts , blisters and pinholes

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First carbon parts , blisters and pinholes

First carbon parts , blisters and pinholes

First carbon parts , blisters and pinholes

Author	Message
taimur	t taimur posted 4 Years Ago HOT Post Details
t Group: Forum Members Posts: 32, Visits: 122	Good work, You made a different look on it.
	Reply Like 2
Nickx	N Nickx posted 4 Years Ago HOT Post Details
N Group: Forum Members Posts: 7, Visits: 168	+x Chris Rogers - 6/3/2020 7:22:41 PM The blisters are there because the resin can't fill the area under the bridged carbon. Carbon is not stretchy - when your bag presses it down, the material on the perimeter can't slide along the surface and over the edge and get pressed into the corners everywhere - so it bridges the corner and resin tries to fill in the gap. It may look like the carbon is under 1-2 mm of clear resin - because it is. It should be doable in one piece without a slip-joint because it is a very shallow part - but you should slip joint the other plies besides the surface one - and your peel ply, perf. film - you should get or make some perforated release film - and breather. If you can leave less carbon on the flange of the part that would help. Sometimes it is good to do a part like this in several pieces - or at least a flange piece and another to cover the cavity. Even if you don't want to do this for cosmetic reasons on the surface layer you should totally do it on the backing plies. -it will help! On the mold porosity, you may have to resurface the mold if the wax doesn't fill it - I am having trouble seeing the pinholes in the pictures. Pinholes in the mold should be bumps of resin in the part in theory but lots of times it doesn't work like that and they just disrupt the surface. Stripping the release and re-gelcoating or priming the mold is an option even though it's a lot of work. I think most of the areas of the parts look really good - except for the problem spots. Slip joints, perforated release film (or painter's plastic with holes punched in it) should help. Do lots of pushing in the corners as the bag sucks - while the wet material can still slide a little. Are you post-painting or clear-coating? Hi thanks !You are right these are bridges .I went back to check the blisters again and there was indeed a layer of 1-2mm of epoxy there.I didn't had this problem with the fiber glass ,but that's not as ridgid as the carbon fiber offcourse. Well these are the steps i did when making the part .First of all i waxed the mold 5-6 times and trying to fill in those pin holes. Second i preformed all the carbon so the weave already stretched into those corners somewhat. Then i applied a layer of resin into the mold and let it cure until B stage.I tried to get out as much air bubbles as possible . Then i did 4 layers of carbon ,with each layer i used my hands and a finned roller to get the weave into the corners and bleed out as much air as possible. I trimmed down the carbon around the mold to prevent too much overhang ,and only then wet out the carbon with resin. I did this for each layer.After that i laid down the peel ply which i also put down as good a possible and uses the finned roller to bleed out as much air as possible. When i bagged the part i pressed down into those corners and vacuumed it in short periods to be sure the bag really gets into those corners. The problem with slip joints is that the b side needs to be as flat (or smooth) as possible cause it sits onto a curved plastic piece . With slip joints i get all kind of bridges on the b side and makes the part not fit properly. I did not had all the right materials to do a proper vacuum bag ,and since i'm new to all this and testing things out i only used the peel ply and breather cloth. That's why i might look into using a vacuum pump and make a vacuum infusion. The downside is i need extend the flanges of my molds even more to be able to apply a vacuum bag with infusion . Resurfacing the mold isn't a option as the fitment will never be as perfect as it is now . The pinholes in the mold do come out as little pins on the carbon ,but i also have tiny holes in the surface layer .That might be air bubbles ? Could it also be that the vacuum storage bag and the vacuum cleaner cannot pull enough vacuum to pull the carbon fiber weave into those corners? I know a vacuum cleaner and a storage vacuum bag isn't a proper vacuum bag to use ,but this was to try some things out. I could also add some gelcoat into those tight corners to make them not as sharp so the carbon doesn't need to go as deep...? I haven't decided yet on what to do post paint or clear coat,depends on how the piece comes out of the mold i guess. Haven't done anything on this piece yet,but i like it to be durable and if possible be polishable. Edited 4 Years Ago by Nickx
	Reply Like 2
Chris Rogers	C Chris Rogers posted 4 Years Ago HOT Post Details
C Group: Forum Members Posts: 120, Visits: 933	The blisters are there because the resin can't fill the area under the bridged carbon. Carbon is not stretchy - when your bag presses it down, the material on the perimeter can't slide along the surface and over the edge and get pressed into the corners everywhere - so it bridges the corner and resin tries to fill in the gap. It may look like the carbon is under 1-2 mm of clear resin - because it is. It should be doable in one piece without a slip-joint because it is a very shallow part - but you should slip joint the other plies besides the surface one - and your peel ply, perf. film - you should get or make some perforated release film - and breather. If you can leave less carbon on the flange of the part that would help. Sometimes it is good to do a part like this in several pieces - or at least a flange piece and another to cover the cavity. Even if you don't want to do this for cosmetic reasons on the surface layer you should totally do it on the backing plies. -it will help! On the mold porosity, you may have to resurface the mold if the wax doesn't fill it - I am having trouble seeing the pinholes in the pictures. Pinholes in the mold should be bumps of resin in the part in theory but lots of times it doesn't work like that and they just disrupt the surface. Stripping the release and re-gelcoating or priming the mold is an option even though it's a lot of work. I think most of the areas of the parts look really good - except for the problem spots. Slip joints, perforated release film (or painter's plastic with holes punched in it) should help. Do lots of pushing in the corners as the bag sucks - while the wet material can still slide a little. Are you post-painting or clear-coating?
	Reply Like 4
Nickx	N Nickx posted 4 Years Ago HOT Topic Details
N Group: Forum Members Posts: 7, Visits: 168	Hi all ,i'm Nick new to this forum and i like to ask some advice on the problems i'm having with making parts out of carbon fiber. I only worked a little with polyester and glassfiber in the past and just recently started using epoxy and mold making with the Easy composites products. I made some paterns and molds for a automotive airduct using the easy composites putty and gel coat. Sadly enough i had to modify the molds and made some repair spots with the gel coat.The mold has several pin holes ,mostly around corners. I asked the easy composites staff before if i could repair the pinholes and they said i could either try to fill them with epoxy gel coat or leave them as is . They said the release wax will fill in the pin holes anyway.Well that isn't true from my experience. I started with a test piece and used 4 layers of 280gr/m² of glass fiber and epoxy resin .I initially wanted to do just a wet lay up but also wanting to try out some vacuum bagging if possible. With the test piece i got some trouble of the fiber cloth not staying into the corners ,so after the 4 layers i decided to use a storage vacuum bag and some peel ply and breather cloth to keep the glass fiber into the corners. This worked out pretty good except the surface had pin holes and some blisters.(the epoxy i used needed a post curing of 15h at 60°C) and i think air got trapped and with post curing it made a blister. I decided to order some new epoxy and some non shift 200gr/m² carbon fiber and try this again .The non shift carbon could be preformed by heating it a little so i thought this would help with keeping the carbon fiber into the corners. This actually worked much easier then the glass fiber of 280gr/m² ,The corners still had to be pushed in to keep them in. This resin also required post curing and i think there was air between the carbon fiber and the first layer of epoxy. which also gave me blisters. To be clear i laid a layer of epoxy resin in the mold ,let it cure untill sticky and then laid down the carbon fiber reinforcement with peel ply and breather cloth and bagged the whole thing into a vacuum storage bag. Should i look into going over to vacuum infusion and use a proper vacuum pump to get better results without blisters? What can i do to remove the pinholes from the mold without making a entire new mold?
	Reply Like 3

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