Mmmm, I'm not really sure I understand the question so apologies in advance...

Aragon was a small Christian kingdom in the Pyrenees that got into a dynastic union with the Catalan counties ruled by the count of Barcelona in 1137 when king Ramiro II married off his daughter and heir, aged 1, to Count Ramon Berenguer IV. Starting with their son Alfonso, both Catalonia and Aragon had the same monarch though kept separate institutions. There also was a lot of rivalry between nobles of the two realms.

As the Crown of Aragon, as it is referred to now, expanded to the south and the west the newly conquered lands were settled by Catalans (the Balearic islands, the coast of Valencia, the city of Alghero in Sardinia) or the Aragonese (Valencian hinterland).

As the royal title of Aragon took precedence before that of mere counts of Barcelona, the resulting confederation was known as the Crown of Aragon. However, legal and cultural distinction between Aragon and Catalonia persisted until the Crown was abolished in the early 18th century. So one had to be an outsider to call the Catalans Aragonese (as their Sicilian subjects seem to have done, for example). On the inside the distinction was quite clear-cut. So no, the two terms are not interchangeable.

Oh, and by the time of the union with Castile the original Catalan counties were in decline and the powerhouse was actually Valencia, a separate kingdom within the Crown of Aragon.