What electric isolator material?

Andy Haard

Hi all
I need some suggestions on what material to use, hope you guys can help me.
It needs to be an electric isolator, as rigid and stiff as possible without being brittle.
I must be able to drill holes into it and put some pressure on it without it cracking and it needs to be as durable in -40 C as in +80C. I will use it in bars 8mm thick by 15mm wide and in length of about 180mm
/Andy

streeters

Is it held in tension or compression?
What scale of production are you looking at?

You have a couple of options, really.

a High Toughness Ceramic - it may be overkill as they are most useful at very high temperatures, but Si3N4 or SiAlON might work. Drilling holes in it would be difficult, could you put the holes in in the die stage? Stabilised zirconia, i.e Ceria or Yttria Stablised Zirconia (YSZ) has excellent toughness, but again the ceramic-aspect of it means it is difficult to machine.

A composite may work, if the load is along a single axis. Again, the loading direction matters. You could just use a laminate at 0/60/120 degree layers or 0/45/90 to spread out the load in the plane. you can get pretty cheap pre-preg matting and cut it into shape.

It depends on the specifics of the part really. Was this any help at all?

Andy Haard

Thanks streeters, they will be pressed together, the 15mm sides against eachother, 75 of them. Between each pair will be two thin alu tabs. It is not for series production.
It is for building battery packs for these cells:
http://blog.evtv.me/store/proddetail.php?prod=123
The idea is to have two stainless threaded rods running though all 75 isolators with bolts at each end and compress it all together. It is to go into a car so it must be able to handle vibrations and temperature.
Would be nice if I could use acrylic but I'm not sure it will stand the stress.
Over on mechanicaldesignforum, Hylam was suggested.
/Andy

M Quack

Why not use some fiber glass like G10/G11? You will need to isolate your tie rods through the Al parts.

Andy Haard

That's an excellent suggestion Mquack! I'll look into that :-)

Against_Laws

What about HDPE?

Danger

At the risk of sounding primitive, how about wood?

Enthalpy

You can buy rods and plates of epoxy +glass fibre. The fibre can even be unwoven short whiskers, if you want isotropic properties (which starts with: no delamination...)