Available Positions

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

Friday, January 1, 2021

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.