No, your principal is safe as long as it is insured up to whatever amount is stated by the institution through which you deal, around $100,000. The FDIC insures the principal back and the interest payments. However, they don't keep pace with inflation and tax increases as the interest rates are very low.
Please correct me if I'm wrong, my Macroeconomics 102 isn't exactly up to snuff
Good luck, not that you need it if you have enough money to live off the interest of a CD
P.S. - Probably best you ask the bank or whatever institution you're dealing with also.