Forces around a bolt hole in a plastic part.
Forces around a bolt hole in a plastic part.
(OP)
I'm trying to understand why I am seeing cracks around bolt holes in a polycarbonate part that is made out of 1/8" thick sheet. I understand that PC is subject to environmental stress cracking, which involves chemicals accelerating small micro cracks under tension. What I'm struggling with is whether a clamping force of a fastener will result in hoop stress around the bolt hole. I thought this was a simple phenomenon, but I can't find any information on it so I'm starting to doubt my intuition. Does a clamping or compression force of a fastener going through the hole impart a resulting hoop stress around that hole? Thanks in advance.






RE: Forces around a bolt hole in a plastic part.
RE: Forces around a bolt hole in a plastic part.
Not widely understood; PC is subject to Environmental Stress Cracking, even from normally innocuous fluids used to cool drills.
Much more widely not understood; the cracking doesn't always occur immediately after contact with the fluid. ... and still occurs even if the fluid exposure is brief, and the fluid is immediately removed, and the PC washed with a compatible soap and water. ... and still occurs even if the cleaned part is stored in a protected environment for substantial time, pretty much immediately when the stress is applied. I.e., the environmental exposure and the stress application can be displaced in time, and cracking still occurs.
Mike Halloran
Pembroke Pines, FL, USA
RE: Forces around a bolt hole in a plastic part.
Chris DeArmitt PhD FRSC
President
Plastic materials consultant to the Fortune 100
www.phantomplastics.com
RE: Forces around a bolt hole in a plastic part.
RE: Forces around a bolt hole in a plastic part.
... and make the axial load large enough to shrink the ID into contact with the bolt.
... and keep going with more axial load.
Mike Halloran
Pembroke Pines, FL, USA