Practice Bottom Bracket Carbon Fiber Layup

Here is the core assembled into the practice tubes and the pivot and BB have been capped with printed parts.
3D printed frame transition core for frame bottom bracket area

Layup complete and wrapped with elastic banding. Areas around the pivot and BB are very hard to wrap and apply effective compression. Any area with a concave shape is bridged by the band and is not compressed upon. This is a very important takeaway and I will need to integrate that concept into the design of the final core surfaces.
Carbon composite layup over printed transition core then wrapped for compaction

Assembly put into the vacuum bag. I think the bagging is no longer necessary. I have not been finding resin in the breather material, so I suspect the elastic banding is suitable for compression and also absorption of the expunged resin.
Composite bike frame bottom bracket layup vacuum bagging

Very happy with the surface finish resulting from the polyester elastic band. The concave areas did not compress sufficiently due to bridging of the band. This will be rectified with proper design of the final core shape.
Resulting composite bottom bracket transition

Resulting composite bottom bracket transition with caps removed

Why do I have to remove the core material? Can the core simply be entombed? What is the weight penalty? Would there be negative consequences and drawbacks of leaving a printed PLA core inside a carbon fiber bicycle?

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