surface coating for hardness

[MikeDrummond]

I am asking for suggestions to make or coat a carbon/epoxy surface to prevent scratching from grit.

The airfoil section is made in a female mold so a sheet of hard stuff could be laminated with the carbon.

The airfoil is rectangular - there are no compound curves.

Is it possible to chromium plate epoxy-carbon?

What about adding carborundum powder or Si-C fibres?

thanks for any help
mike

 

[prasheela]

hi mike,
you can electroplate epoxy carbon composite for corrosion prevention from the saline water. better way than electroplating is to use polyurethane based gelcoat. this gives you both abrasion resistance and corrosion resistance.
for more clarificaion you can contact me at HGP@LM.CO.IN

 

[polymire]

OK
there are two different erosion mechanisms that you can protect against....

impingement
sliding wear (including powder or grit sliding back and forward across the surface).

The impingement protection can be done by many different materials.

.010 thick stainless steel bonded onto the surface with epoxy adhesive.

.024 thick flurocarbon rubber (Viton) sheet bonded with epoxy.

.010 thick AF32 Nitrile Phenolic (sold by 3M).

generally you want a coating that is very hard, for example the steel sheet material. In aerospace aplications, the large bonded sheets do not work too well because at elevated temperatures the thermal fight between the steel and the composite can lead to peel of the adhesive. However if you are operating at a low temperature this might work well. (it is simple and can be repaired).

The alternate is to apply a coating that is quite soft (soft enough that you can dig your fingernail into the coating and leave an impression). Most sand protection coatings aplied to radomes and leading edges of wings are based on soft aliphatic polyurethane. However this would probably not work in a marine environment because the soft polyurethanes can degrade due to hydrolisis.

I would recommend the AF32 coating. But first check with 3M regarding prolonged exposure to marine environments.

If you expect Sliding wear, for example sand piling up against the surface and moving back and forth then the soft coatings do not work as well as hard and strong coatings, eg sheet steel.