There are different strengths of Velcro adhesive. The usual ones do not stick well; however, the industrial strength ones can stick very well. You are more apt to find the industrial strength velcro in a big box hardware store. I don't think I've ever seen the industrial strength Velcro at JoAnn's or other sewing shops.
The really strong adhesive velcro will have "industrial strength" printed on the packaging.
What is the project? If the velcro will be taken apart and re-aligned on a daily basis, then even the industrial strength adhesive may not hold. Your best bet may be to purchase a small amount, then put it on your fabric and make sure it is going to hold the way you need it to hold before investing in a large amount.
Edit: I am talking about the adhesive-backed velcro. Iron-on does not come in industrial strength as far as I know. Here is a link to the type I am talking about
:
http://www.amazon.com/Velcro-Industr...dp/B00006RSP1/