Polymers under hydrostatic loading

[tsurani]

Hi,
Can someone please provide some insight into the behaviour of polymers (eg ABS, Nylon, Delrin) subject to very high pressures (~550MPa), while in a controlled volume (~60mm diameter x ~150mm long. Obviously there is some compression, but what happens next? I would imagine that in some more brittle polymers, cracking occurs. Are there any polymers that do not 'fail' in this type of loading environment?

Any info would be greatly appreciated.

Cheers,
Tsurani

 

[rnd2]

tsurani

Assuming controlled volume means the polymer starts off as a solid cylinder, unrestrained with nom dia. 60.0mm x len. 120.0mm. Compression direction is longitudinal.
At 550MPa and normal room temp say 20 deg.C I expect brittle polymers will fail in shear long before anywhere near 550MPa and soft mega-long chain polymers like uhmwpe and ptfe will deform plastically but not crack. Probably a bit of both for nylon. Now if the polymer became warm during the compression............
A way to get a polymer not to "fail" given the criteria listed would be to heavily fill say a superior epoxy resin in the longitudinal direction with something like high tensile steel or carbon fibres ........but then its a composite.

 

[tsurani]

rnd2,
thanks for the response. you've managed to confirm my own thoughts on the matter. w.r.t ptfe, as you say, it would likely plastically deform, but not crack but i expect that under this loading environment the bulk modulus would come into play (reduction in volume), and eventually the molecular structure would break down. ive decided not to investigate polymers further for this application.
cheers,

tsurani

"Catapultam habeo. Nisi pecuniam omnem mihi dabis, ad caput tuum saxum immane mittam."