Introduction to Mechanical Characteristics in Polymeric Solids: Lecture 5: Structural Explanation for Tensile Behavior of Polymer Solids

The tensile deformation behavior of semicrystalline polymer solids is discussed from a structural viewpoint, with emphasis on yielding, necking, and strain hardening. Molecular orientation scarcely develops from the onset of deformation to the yield point, whereas pronounced orientation appears during post-yield deformation and necking. Yielding triggers fragmentation of lamellar assemblies and collapse of the spherulitic structure, leading to cooperative rearrangement of lamellar cluster units. Subsequent strain hardening in the ultra-drawing regime is governed by the progressive formation of taut tie molecules extracted from the crystalline phase.