Thickness control at sharp curvature.

[BadenPowell]

Hi i was wondering if anyone here as had experience resolving issues of over thickening at radius (example: corner of a U-shaped plate). I suspect the radius of curvature is too small at the bend, and is restricting resin flow, hence leading to areas where thickness becomes too high. A possible solution I was thinking was to reposition (or add) vacuum ports closer to the other side of the radius to assist with the flow.

Has anyone come across this issue and could provide some insight? Thanks in advance.

 

[Compositepro]

Increased thickness in female curvatures is a common problem due to bridging of reinforcement fibers or bagging materials. Common solutions include placing overlap splices in the reinforcement and breather layers at the corners so that the layers can slip and conform to the mold surface. Bags should be pleated in corners to avoid bridging. Also, pressure intensifiers are used to push material into the corners. These are usually hard rubber that has previously been molded to the desired shape of the inside corner radius of the part, forming, in effect, a two sided mold in the corner area.

 

[BadenPowell]

Thanks for your input Compositepro. I can see how a rubber material (ie. rubber sheet) could help even out the "vacuum pressure" in a tight corner, effectively pushing down against the "bridging fibers".

 

[Compositepro]

A flat rubber sheet will not help, but make the problem worse. It must be a pre-molded rubber shape, which often is made from sheet rubber.

 

[BadenPowell]

Hey compositepro,

Thanks again for your input.

I was thinking along the lines of a thin rubber sheet which could conform the the contour more easily than a stiffer rubber sheet under vacuum. If the solution calls for essentially a rubber male mold, then I imagine it would take more than just the vacuum pressure to consolidate the intensifier against the ply.

 

[Compositepro]

http://www.airtechintl.com/en/Airpad-Rubber-Tooling

https://www.google.com/search?q=vacuum+bag+pressure+intensifier&ie=utf-8&oe=utf-8