Available Positions

Study of recently observed extreme mechanical properties in epoxy fibers, and of the molecular mechanism leading to such behavior

3-4 
Year(s)
Area: 
Chemistry
Thursday, October 3, 2019

The candidate will study the ductility, necking behavior, and size effect in highly cross-linked epoxy fibers and possibly in model composites. The question of potential macromolecular re-alignment is a highly counter-intuitive conjecture because unlike semi-crystalline polymers, or even lightly cross-linked polymers, epoxy is an amorphous polymer which forms 3D rigid interconnects when cured, thus a macromolecular network with very little propensity to flow. Despite this apparent conceptual obstacle, first evidence of molecular (re)orientation in an epoxy fiber was recently obtained by Wide Angle X-ray Scattering (WAXS). If molecular (re)orientation is indeed confirmed, an explanation/mechanism will have to be proposed for such unexpected observation. This might involve reordering of polymer segments, distortion of crosslinks, or other molecular-scale structural changes, which would favor mechanisms leading to high strength, stiffness and plasticity.