Nah mate the windscreens are made out of plastic. The ash is basically very fine particles of glass. The big aircraft screens are made out of glass and they get eaten by it. 90knts glass particles against plastic will just pit and I would imagine its not outside the range of possibilty to actually eat right the way through. Even if you flying in clear air there will still be particles dropping out below causing damage.
All your paint work will be shot blasted as well.
And the particles would also get sucked up into the engine. The filter might be able to take some of them out but as soon as you use the carb heat you will get them into the cylinders, the liners are very soft, you will basically turn your oil system into a liquid emery scourer (Emery paper which we call sandpaper is made out of volcanic ash)