CD's are essentially bonds. When you buy a CD then you are agreeing to loan your money for a set amount of time at an agreed upon interest rate to a bank. When you buy a bond then you are agreeing to loan your money for a set amount of time at an agreed upon interest rate to the government or corporate entity.
Do you see the difference? There really is none.
CD's, bonds, and bond funds may lose 'value' temporarily during periods of rising interest rate, like we are currently in. You only lock in those losses if you sell before maturity or before the 'average duration' within you fund. Google "Bond interest rate risk".
The problem with CD's is that they usually return less than bonds in the long term. Even today.
term US Treasury Ally CD CapOne CD Marcus CD Barclay's CD
3 mo 2.38 0.75 - - 0.35
6 mo 2.52 1.00 0.60 0.60 0.65
12 mo 2.66 2.65 2.60 2.55 2.55
2 yr 2.79 2.60 2.70 2.60 2.60
5 yr 2.87 3.10 3.10 3.10 3.10
10 yr 3.06 - - - -
20 yr 3.22 - - - -
30 yr 3.32 - - - -
The only term that beats the treasury is the 5-year, and it's probably not that great of a buy right now. And when you factor in taxes, the treasury probably comes out ahead (treasuries are not taxed at state and local levels).
There's more to consider than the interest rate though. Liquidity is one, no state income tax on Treasuries is another, if held in a retirement account (bond funds, usually) then there are additional tax benefits.
I will probably never buy a CD. I don't see the point.