Crushed glass fibers by joining screw

[drodrig]

Hi there,

We are building some supporting plates made of G10 (FR4) due to its good mechanical properties and low thermal conductivity.

It is the first time we design something made of glass fiber and we have some concerns.

We managed to design the plates without making threads on the G10. On one side we will glue it and on the other side we will screw it to another threaded aluminiuim alloy part part.

For this second side we need to press the G10 with the screws head. I am concerned about breaking/damaging the fibers with the screw head.

Attached some pictures showing the setup. We use conical head screws to save space (we might find space for flat head and washers).

There are 2 positioning pins and two screws. Are positioning pins reliable on G10?

I have heard something about putting in some bushings, but I understand the bushing will press the fibers too.

How could we connect the plate?

thank you

 

[Compositepro]

It probably is not a problem but, the location of your clamping screws relative to the flexing composite bars looks "odd" to me. You basically have cantelevered clamping bars that are at 90 degrees to the flexing bars. This will result in a higher clamping load on one side of the flexing bar and a very complex load pattern.

Also the thickness of the clamping bar relative to the flex bar seems low, particularly since it is cantelevered. Flexing of the clamping bar means movement and therefore fretting.

 

[drodrig]

Compositepro,

Thanks for your remarks.

These flexing bars are indeed in cantilever position. They are G10 plates with holes (for positioning pins H7/h6 and let the pressing screws go through).

This layout with plates (and not a complicated geometry, mechining the G10) looked good.

How else can one use the G10 for the cantilever load?

The thin bar has this thickness because of space reasons. I'll try to get it thicker; also try to use conical head screws

thanks