Very strong polymeric materials could be prepared if molecules of infinite length are arranged in an extended configuration. Because of their high strength to weight ratio, ultra-high molecular weight polyethylene (UHMWPE) fibers present great promises for weight-sensitive applications, such as military protective equipment. However, the mechanical properties of the fibers are weaker than the theoretical values. To specify the origin of this discrepancy, one has to examine the influence of small imperfections, i.e. the microstructure.
This work aimed, first, at developing a reliable micromechanical model of the fiber, and second, at determining the elastic and plastic deformation mechanisms. We developed and verified a micromechanical model focusing on the impact of the morphology and the mechanical properties.
In the elastic domain, the results were similar to the classical composite theory. In the plastic domain, we determined the most influential slip mechanisms of the different crystals in the structure according to the direction of the loading, such as chain pull out or kink bands formation.
This project was part of a large collaboration where experimental and numerical teams at multiple scales shared and confronted results to understand the origin of the macroscopic behavior of these fibers.