Fibers compression performance, which parameters?

[Joao Freitas]

Dear all,
Dyneema fibers has a poor performance in compression, even worse than aramid fibers; yet they present a very high tensile strength.

My question is: which the parameters determine the compressive performance of a polymer?.

I think it might be related with the presence of a stiff backbone chain (containing lots of aromatic rings, for instance) and probably the amount of secondary bonding (namely hydrogen bonding), but I am not quite sure about this.
Thanks in advance.

João Freitas

 

[Compositepro]

The reasons are quite simple. Tensile strength comes from a high degree of alignment of the polymer molecules, which have a very high aspect ratio as fibers do on a macro scale. This alignment is created by doing a lot of stretching of fibers during the manufacturing process. Breaking highly oriented fibers requires breaking chemical bonds in the backbone of the molecules rather than the weaker bonds holding different molecules together. Tensile loads increase orientation and strength.

Compression loading causes fibers and molecules disorient and to buckle. You cannot push with a piece of string.