As with most weapon construction questions, you will need to refer to specific chapters as to whether they would or wouldn't pass a specific weapon.
The Alliance Rulebook does not explicitly disallow curved or jointed cores. It does, however, disallow any core in a crossguard (which seems to be the most common purpose behind a jointed core). There are some specific chapters which might disallow jointed cores or curved cores, but remember that the ARB allows alternative weapon construction which you can propose to your chapter's marshals.
The most important requirement is always that the weapon be safe. This judgement might vary from chapter to chapter due to climate, specific experiences with certain weapon construction methods, or different interpretations of what constitutes a safe weapon.
-Bryan Gregory
ARC
