Shear testing Jig for Plastic 2

[mark20]

HI people,
I'm currently involved in a project where the goal is to design a shear testing jig.
I have looked through various standards but to no avail.
Does anyone know where i can find any information on designing such a jig to get accurate results for testing plasics.
I have already done a basic double shear 't' bar test jig design but i am unsure of whether or not this is a valid shear test for a plastic.
HHHHHEEEEEEEELLLLLPPPPP!!!!!

Thanks.
Mark.

 

[BLN]

Don't know if you've checked these standards, but they may be worth a look:

ASTM D732 - Shear strength of plastics by punch tool
ASTM D3846 - In plane shear of reinforced plastics
ASTM D4475 - Apparent horizontal shear of plastic rods

We don't test the plastics, but we do test adhesive bonds. A jig we've used utilizes a square sample (sandwich in our case). The sample fits in a recess in the jig and only exposes a small cross sectional area. Maybe you could try something like that.

 

[mark20]

Hi BLN,
Thanks for your reply I have already looked at 2 of these standards with no luck. With your jig was there any limit or tolerance needed between your punch & die in the shear plane or does it have to just be as close as possible?
Is there any standards for this type of thing, or general laws.
Or am i talking complete rubbish?

Should i just design the simple punch and die jig?

Thanks
Mark.

 

[BLN]

I haven't been involved in this testing, but went back over a presentation to find out more details. The test involves making a modified Iosipescu V-notched beam fixture. Instead of the sample following the dimensions of the sample, the fixture is in the shape of the sample, with the recess for the actual sample. Since I haven't been directly involved, I'm not sure of specific dimensions and/or tolerances. The test method called out is: ASTM D5379/D5379M-98 Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam.

Sorry I can't provide more specifics. From the presentation it appears that (in our case) the only part of the actual sample exposed is the bondline. The rest of the fixture is in the configuration of the V-notch Beam. Hope this helps a little more.