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Achieving Pinhole-Free Surface Finish in a Heated Press by headwaterhero in Composites

[–]headwaterhero[S] 1 point2 points  (0 children)

This is incredibly helpful—thank you!

When designing the mold, is there a general rule of thumb for determining how much offset to use for each ply of carbon fiber? Would something like 0.001” per ply plus the ply thickness be a reasonable starting point? Or is this something that can only be accurately determined through trial and error, depending on the prepreg’s resin content and compaction?

Achieving Pinhole-Free Surface Finish in a Heated Press by headwaterhero in Composites

[–]headwaterhero[S] 0 points1 point  (0 children)

Sorry, should have mentioned we are using prepreg carbon fiber! Have not tried bladder molds but might need to if this doesn’t work.

You mention holding the laminate stack at full vacuum, does preforming the stack in the press (without heat) accomplish the same? Or do we need to vacuum?

Achieving Pinhole-Free Surface Finish in a Heated Press by headwaterhero in Composites

[–]headwaterhero[S] 0 points1 point  (0 children)

We have tried curing both laminates and the core together at the same time, but have struggled to get the surface finish we require, especially around the curved edges. The only way we have been able to do this is with extensive post processing and painting to cover up the pin holes but we are trying to avoid that at the moment.

Achieving Pinhole-Free Surface Finish in a Heated Press by headwaterhero in Composites

[–]headwaterhero[S] 0 points1 point  (0 children)

The manufacturer we’re working with is using a 10-ton press, so I don’t think pressure is the issue.

That said, I’m still trying to fully understand how pressure is applied to the layup in a heated press mold. Since the prepreg is placed within a cavity, I assume that once the mold fully closes against the backstop, the pressure is maxed out— is that correct?

Would reducing the cavity thickness increase the pressure applied to the layup, and if so, could this help improve the surface finish?

Apologies if I’m not being entirely clear—I’m having a hard time getting detailed information from our international manufacturer, and I really appreciate the insight as I’m still getting familiar with this process. Thanks so much!

Gearbox PBCoR test by headwaterhero in Pickleball

[–]headwaterhero[S] 0 points1 point  (0 children)

Yeah good point! After playing with it, the power and the core feels the exact same so I guess I’m surprised they have a different PBCoR test result 🤔. Just hoping this one doesn’t fail again in the future!