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quinn
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Here's a panel I infused 30 hours ago. As you can see in the pics, I have some bubbles in the flow media. Before infusing, I pulled full vacuum and left it for 20 minutes, no vacuum loss. Fully degassed my resin in vacuum before infusion. During the infusion I could see some very tiny bubbles flowing with the resin. Finished the infusion, next morning I could see all these bubbles. Looking through the glass on the finished side, it looks flawless. No voids or bubbles. Probably going to debag it in a couple hours and see how the panel looks. Hopefully bubbles are only in the flow media. So what went wrong? Is it likely I developed a leak somewhere during the infusion? Or I didn't have full vacuum in the first place? My gauge only pulls to 26 but i can boil water with vacuum so it's at least hitting over 29. If I was only getting 29.5 inches or so, would that be bad enough to end up with air like this? Or more likely that it just started leaking at some point? After 30 hours, the bag is still pulled down very tight. I'm also still using regular laminating resin, 600cps, not actual infusion resin.  
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Warren (Staff)
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the tree branching effect is classic of a tiny leak or some trapped air migrating. As it moves it changes direction randomly trying to take the path of least resistance.
I would wait until you demould before panicking too much. As long as the bag stayed tight until it gelled, then chances are you should be fine. or just have a few pinholes.
Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
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quinn
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+xthe tree branching effect is classic of a tiny leak or some trapped air migrating. As it moves it changes direction randomly trying to take the path of least resistance. I would wait until you demould before panicking too much. As long as the bag stayed tight until it gelled, then chances are you should be fine. or just have a few pinholes. Panel came out great. Couple tiny pin holes but fine for my application. First time using frekote. Panel just about fell off the glass, worked great. Could also be a possible cause for the leak. I put down one application of frekote on the whole peice of glass before realizing the tack tape may not stick well. Did my best to clean that first coat off, then taped off where tack tape would go and applied 4 coats of frekote within the taped area. I don't think I got that initial coat off all the way because the tack tape peeled off with very minimal effort when demolding. Might be why I developed a leak. 
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quinn
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So I weighed my plate, 0.26g per square cm at 2mm thick. it's 17% lighter than the commercial plate I have at same thickness. What does that indicate? I didn't think to weigh the dry lay up before infusing so not sure about resin/fiber ratio. Does lighter than average indicate anything specific? Low or high resin/fabric ratio? Good? Bad? Not sure what to make of that.
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oekmont
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To determine the exact resin volume percentage, you have to measure the dimensions of the sample very accurate and calculate backwards starting with the density.
Crp's density can vary between the density of the resin on the lower end, and the density of the fibre on the heavy end. as your panel is less dense than the commercial one, it has to have a higher resin contend. Different epoxys and carbon fibres don't vary that much in density.
Higher resin contend isn't bad out of every perspective. The stiffness and strength against forces along the plane drop about linear with the fibre contend. But usually the critical property is the stiffness when bending the plate. And this drops far less than linear with the resin contend. But the resin contend lowers the density of the plate in a linear way. Because of that, to a certain degree, a more resin rich plate could have a slightly better stiffness to weight ratio when it comes to bending stiffness.
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quinn
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+xTo determine the exact resin volume percentage, you have to measure the dimensions of the sample very accurate and calculate backwards starting with the density. Crp's density can vary between the density of the resin on the lower end, and the density of the fibre on the heavy end. as your panel is less dense than the commercial one, it has to have a higher resin contend. Different epoxys and carbon fibres don't vary that much in density. Higher resin contend isn't bad out of every perspective. The stiffness and strength against forces along the plane drop about linear with the fibre contend. But usually the critical property is the stiffness when bending the plate. And this drops far less than linear with the resin contend. But the resin contend lowers the density of the plate in a linear way. Because of that, to a certain degree, a more resin rich plate could have a slightly better stiffness to weight ratio when it comes to bending stiffness. I haven't done an accurate test yet, but it does appear that my panel is less stiff than the commercial one, but maybe not more than 17% less stiff (weight difference) so like you said, it might still be possible that my panel is as or more efficient than the commercial one on stiffness to weight ratio, but I have a feeling the commercial plate is going to be a bit better. So I'm assumining the reason that I have higher resin content vs commercial panel must just be because they got better consolidation using prepreg and mechanical pressure. is there any way for me to improve resin/fiber ratio without using prepreg and pressing? Or am i probably getting about as good as i can with the current method without huge investment? I know there's potential for me to get a more efficient panel using light core material, but just curious if there's any way to improve my resin/fiber ratio. Not that I'm not happy with the results I got. The panel came out awesome and has a better surface finish than commercial, just not as strong. I guess i was hopeful that my most likely higher grade fabric could yield even better strength than the commercial plate, but obviously the process for which it's made is much more relevant.
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oekmont
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You can get a perfect resin ratio with infusion. This usually means, that you have to close the feed line before the resin front reaches the vacuum line. Ideally to the right time, that the excess resin barely can impregnate the rest of the part. Alternatively you can close the feed line, and let the vacuum line open, until no more resin enters the catch pot.
Both will increase the chances of getting not a perfectly good finish. And the carbon optics are less "deep".
If you decrease your resin ratio, you will get a less stiff plate, as the thickness (wich is the major factor for stiffness) decreases. To get the same thickness, you would have to compensate with additional cloth. This will lead to increased weight for the same thickness, but slightly better rigidity. Basically what I said before, but from a different perspective.
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quinn
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+xYou can get a perfect resin ratio with infusion. This usually means, that you have to close the feed line before the resin front reaches the vacuum line. Ideally to the right time, that the excess resin barely can impregnate the rest of the part. Alternatively you can close the feed line, and let the vacuum line open, until no more resin enters the catch pot. Both will increase the chances of getting not a perfectly good finish. And the carbon optics are less "deep". If you decrease your resin ratio, you will get a less stiff plate, as the thickness (wich is the major factor for stiffness) decreases. To get the same thickness, you would have to compensate with additional cloth. This will lead to increased weight for the same thickness, but slightly better rigidity. Basically what I said before, but from a different perspective. Ah ok. This panel I just did, the resin was setting up right as it finished. Took about 40 minutes, probably because I'm still not using infusion resin, which i will next time. I did close the feed line a little while before vac line, but as I said the resin was already thickening so I'm sure it didn't pull much out. I think I'll get a bit better results next time with proper resin and also experimenting with other fabrics. grade A finish is not important for these parts so I will let it suck out a fair amount of resin at the end next time. Also I'm thinking when I try using some inner layers of non woven biaxial, it should not only improve stiffness a bit from the non kinked weave, but also I would assume it has the potential for lower resin content. Non woven fabric should have less voids for resin to fill, right?
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oekmont
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Yes, slightly. But but don't think that you might experience a difference. The biggest advantage of nonwoven cloths is a better pressure strength along the fibre.
What makes a big difference is the fibre orientation. Do you need the stiffness in multiple directions, or just in one (or two perpendicular directions)? Because if you exchange a woven 0/90 layer with a 45/-45 biax cloth, you loose stiffness along 0° and 90° and gain stiffness along 45° and -45°. The difference gets smaller, the closer the layer is to the neutral fibre (usually the centre of your ply stack. This is why sandwich plates are almost as stiff and strong against bending.
If you need stiffness in just one direction, a unidirectional cloth performs best
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quinn
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+xYes, slightly. But but don't think that you might experience a difference. The biggest advantage of nonwoven cloths is a better pressure strength along the fibre. What makes a big difference is the fibre orientation. Do you need the stiffness in multiple directions, or just in one (or two perpendicular directions)? Because if you exchange a woven 0/90 layer with a 45/-45 biax cloth, you loose stiffness along 0° and 90° and gain stiffness along 45° and -45°. The difference gets smaller, the closer the layer is to the neutral fibre (usually the centre of your ply stack. This is why sandwich plates are almost as stiff and strong against bending. If you need stiffness in just one direction, a unidirectional cloth performs best I need strength at 0/90 mostly, but I assumed there should be 0/90 non woven biaxial available right? If not, alternating layers of uni at 0 and 90 should be essentially the same right?
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