Weed membrane on decking joists

Theoretically you could, but the fabric would hold moister and rot the wood quicker. Just make sure the ground underneath is cleared of weeds and any green and lay down you're fabric and put chuckies on top or any equivalent. Purely depends why you're wanting the fabric on the joists if it's for water use dpc.

Membrane on the surface of Decking joists is a not an option! All timber needs to have air flow,to prevent the natural movement of the timbers fibres,and reduce the ageing process, and degradation. Any membrane should be secured upon the ground surface, preferably with granular aggregates below the structural joists

Weed membrane does not hold water It should not be suspended as its not designed for that purpose

You must retain air gaps