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Old 07-31-2013, 10:36 PM   #1
Tominator

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Default Attempt at an OOA cure using normal prepreg

Hello everyone,
I was wondering what everyone thought of my surface finish here on my project. Basically, I made a solid aluminum male mold that has an octagon shape to it. It is supposed to be a pencil holder. It's the prototype, so I didnt nail it my first try.

For the layup, I used 5 layers of a 3k prepreg. I think the weave is satin. I didn't debulk between layers, but I did have it dwell for an hour and a half at 200 F. Then ramped up to 300 for 4 hours. The inside of the box came out nice. The only problem was the resin did not fill some of the weave creating the pattern shown in the photo.

Is this type of finish pattern always going to happen? I haven't seen that type of finish on the internet.

I have been looking into OOA prepreg in small qauntities is the Easy-preg from the UK which costs $172 a yard! not including shipping. http://www.easycomposites.co.uk/prod...ace-layer.aspx

I was thinking of not using breather to get more compaction and using just non-perf film instead to capture the resin in hope it will fill all that in.

Any thoughts?

Thanks,
Tom
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Old 08-01-2013, 01:58 AM   #2
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If enough people bunch up, you can buy a roll of Umeco VTF261. It costs 50 a metre, but you have to order a 50 metre roll. Easy-preg is a rebranded VTF261. It is pretty unique, and no other manufacturer has made anything like it. I need about 5-10 metres, the user morepower uses it too, and I know someone else that might want some.
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Old 08-01-2013, 08:36 AM   #3
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I might be interested. Im going to try a few different tricks with stuff i have now first though.
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Old 08-01-2013, 09:04 AM   #4
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I can't tell whats going on in your photo.
Is that the part in the mould?
Is the mould male or female?
You say the inside of the box came out nice, but your photo IS the inside. (?)
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Old 08-01-2013, 09:09 AM   #5
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De-bulks are critical in ensuring your plys are down. At a minimum, suck down the first ply, then every 3rd or 4th ply from there on out. What were you using for edge breathing?
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Old 08-01-2013, 09:40 AM   #6
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CC-The part is a box. The mold is male. The picture you see is the inside of the box. The outside of the box isn't as nice as the inside. It got a little wrinkled. Partly because i used two layers of breather which i wont do next time.

Cleuk-What is edge breathing? I just covered all carbon surface with peel ply, perf, then breather.
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Old 08-01-2013, 09:41 AM   #7
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From what I can see of your photo it looks like there are small dry areas on the weave intersections, This is usually caused by being resin dry(ie not enough resin) on the first layer. Try a prepreg with a higher resin content(possibly on the first layer only).
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Old 08-01-2013, 03:12 PM   #8
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Yeah, i thought about that. I was thinking of using no peel ply and see if i can keep some of the resin to stay on the surface to fill in the weave.
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Old 08-02-2013, 01:05 AM   #9
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I see. The part is so small that you don't really need breather. If anything it's probably reducing pressure. Instead, put glass tows on each corner, on the flange surface, running into the outside of the mould and into a patch of breather under the valve.
I'm assuming the outside is what matters aesthetically, you should use a female mould.
What prepreg are you using?
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Old 08-02-2013, 02:53 AM   #10
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Maybe its just me but I cant see the pic in any size so cant really see whats going on there. But debulk surely, always a good practice.
What pre-preg are you using? Is it an autoclave pre-preg? Most autoclave pre-pregs are designed to work in an autoclave at high pressure which forces air and volatiles into solution due to the pressure. This is then removed with the vacuum. Out of autoclave pre-pregs achieve porosity reduction by extraction prior to gelation of the resin so in effect the resin rheology is tailored for each application. Summary is not to use autoclave pre-pregs out of high pressure scenarios.
Btw, dont buy from Easy Composites if you’re in the US, loads of low-volume OOA pre-preg suppliers there Im sure
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