Both players have agreed two-year deals with the club, with Fiji international Ma'afu joining from West Harbour Pirates in Sydney, while Copeland arrives from Championship outfit Rotherham Titans.
"A big thing for us as a region and a team is that we should be looking at a three-year cycle of establishing a group of players that will be here to build for the future," said forwards coach Justin Burnell.
"Robin is a big physical boy with the ability to cross the gain-line but has the skills and finesse to put people in to finish via his decision making.
"He is 24 years old and has been the outstanding player in the Championship this year. We watched his games a few times, assessed his performances and then viewed him and met him.
"Campese Ma'afu came to my attention in the 16-16 against Wales.
"I thought he did well in the scrum in certain aspects against Adam Jones, who as we know, is one of the best tight-heads in the world. To see him scrum in the World Cup and against New Zealand in the warm up games showed he's an exciting prospect."
The Blues were beaten 33-12 by Ospreys on Saturday.