Can food processors be used as a blender ?!

Food processors won't work as well as blenders for thoroughly pulverizing things (like smoothies, etc) because of the way they're shaped on the bottom. Food processors are wide and flat, whereas blenders are narrow and cuved so that all the food inside is forced down around the blades extremely well.
If you don't need that level of pulverizing though, you could get somewhat similar results with a food processor...don't know how well they handle ice though.

Yes. I use mine that way. It's good for making smoothies as well as for chopping food. It is also great for blending ingredients, like you would if you were making soup.

It isn't the best way to make them but they will do.