[Nocturnal]

The AI will generally trade if you give them a good offer. More resources of any type tend to be accepted, and when trading ships, I suspect that they just calculate tonnage to consider whether to trade. So I offer equal tonnage of ships in addition to resources.

In a single-player game with no tech trading and significant AI bonuses, I traded old or badly damaged ships along with resources for the AI's high-tech ships. They didn't seem to mind, though a few races refused to trade with me unless I gave them an extremely generous offer, or used the pleading/demanding tone where appropriate.