Compressive properties of UHMWPE fiber composite vs. tensile.

[RPstress]

I have been looking into ultra high molecular weight polyethylene (UHMWPE) fibres and haven't found much on the web about their properties in composites. I'm aware that they are hard to stick to, but I'm still interested in composites made from them.

Does anyone have any experience of polymer matrix composites with these fibers? (I believe Spectra and Dyneema are the only options at present.)

I'm particularly interested in how the compressive properties stand up compared with the tensile ones, so a property value for an all-0 degree laminate would be good. (Compression seems to be a bit of a bugbear for these organic fibers, with Kevlar, PBO, M5, etc., all having poor basic fiber properties in compression.)

 

[Compositepro]

The compressive properties of the polyethylene fibers are poor so it is not easy to find data. The fibers just aren't used where there are significant compressive loads. For Kevlar 49 the 0 degree composite tensile strength is listed as 200,000 psi but the compression strength is 40,000 ksi, which is probably not much higher than the epoxy used in the composite. The fiber will creep long before it get to an ultimate stress, so I guess the matrix would have to carry much of the load.

I saw a fishing rod made from Kevlar/epoxy once. It was made just to see what would happen. It behaved like ductile steel. If you bent it, it stayed bent.

 

[RPstress]

Thanks. That pretty much answers my question. I'd still like a couple of numbers (compression strength and modulus if poss.), if anyone's got them, but basically it's rubbish in compression, like all other organics that I know of.

Anyone have more than rumours of M5's properties? I notice their website has changed, and I heard they've been due to start a pilot plant for a while.