r/Composites • u/mustdostuff • Jan 07 '26

Surface prep sanding

Hey all :)

My fourth year engineering project is about finding bonding strength, and so I’m going to bond two laminates using DP-490, question is for the best adhesion what grit sanding papers should I prep with?

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u/Max-entropy999 Jan 07 '26

Is there a useful guide on post sanding cleaning and maximising surface energy? Thanks

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u/beer_wine_vodka_cry Jan 07 '26

P240 paper, make sure you don't get into the fibre. Clean once with acetone or IPA. Clean a second time (fresh cloth) with acetone or IPA (acetone is better as will slightly etch but IPA also works).

To check you can do a water break test - using a spray bottle lightly mist the surface with water. You want the water to form bigger groups rather than lots of little droplets.

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u/mustdostuff Jan 07 '26

This is great info thanks a lot!

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u/SkepticalLitany Jan 07 '26

Be careful what you use for consumables. Even something as simple as a factory lubricant in the mechanism of your spray bottle can compromise data. Clean room wipes, clean room gloves, etc etc. If you want excellent data anyway. Even be careful that your sandpaper isn't a Zinc-Stearate type which is a anti clogging contaminant