By zappafile123 - 4/8/2020 12:09:41 PM
Hi there,
I'm new to making CF products and am after some tips on how to achieve a high gloss finish on the peel ply or B side of a small part made with resin infusion. Specifically I'm making custom road cycling shoes using a plaster casts of my feet. I successfully made my first sole on the weekend (laying up the carbon over the foot cast followed by peel ply and a full vacuum bag enveloping the entire foot cast), but have encountered the minor problem of requiring a smooth finish on the inside and outside of a part. I need a smooth finish on the inside so my foot is comfortable, and a neat finish on the outside so it looks good. As you can see from the first two images below, the peel ply leaves a pretty rough finish and I'm guessing from what I've read that thats just what peel ply does no matter what. What can do to make it look good like the third image below? I guess I could make a second carbon mould over the top and use that to sandwich the carbon, but that's too much effort, especially if I want to make shoes for local cyclists to get a bit of cash on the side of my day job. Would painting on some extra resin after moulding and then sanding and buffing it work?
Further, I imagine I ended up with those big wrinkles on the outside finish because I wast careful about how I applied the peel ply. Tips on getting that smooth are also welcomed (just use adhesive? (cause I didnt!))
Thanks in advance!
 notice the gloss finish inside and outside the shoe
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By Hanaldo - 4/15/2020 2:32:14 AM
I do mean wet-lay vacuum bagging, not just wet-lay with no vacuum. You can wet the reinforcement out in between two sheets of plastic film, and then allow it to cure to a b-stage before placing it into the mould. In this way, you can work with the material almost exactly as you would a pre-preg.
Getting a smooth b-side is much easier with wet-lay and pre-preg than infusion because you dont need the flow media. So you can then use a matched mould, whether that is a rigid matched mould or a silicone matched mould - either way it is easy. Infusion it is very difficult and virtually impossible, you would be looking at more of an RTM process to achieve the same thing.
As for bonding, your choice of adhesive is fine, thats not the issue. All structural adhesives will be stronger than the laminate - provided the bond joint is designed correctly. I'm not sure what your bond joint looks like, it is hard to tell from the photos. My first comment was based on your photo where it appeared like you would be butt-joining the upper to the lower. If that is not the case and you have a good overlap between the two components (at least 25mm, which looks to be the case in your latest photos), then that is fine, it will be strong. The only thing that could be an issue is elongation - is the 3M DP420 a rigid adhesive or a flexible adhesive? You would want a very flexible adhesive to bond will with a flexible epoxy, otherwise all of that movement will either be made impossible by the adhesive, or it will cause the adhesive to fail over time.
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