Understanding fracture and fatigue at the chemical bond scale: Potential of raman spectroscopy

Abstract

Coupled mechanical and Raman analysis of a material under tension or compression provides much information on the material’s (nano)structure. Raman extensometry can be applied to synthetic and natural polymer fibers (e.g., polyamides [polyamide 66], polyethyleneterephthalate, polypropylene, poly[paraphenylene benzobisoxazole], keratin/hair, and silkworm and spider silks). The technique allows differentiation between crystalline and amorphous macromolecules. Bonding is similar in the two cases, but each exhibits different Raman signatures, especially at low wavenumbers, and a broader distribution of conformations is observed for amorphous macromolecules. These conclusions are used to discuss modifications induced by the application of a tensile or compressive stress up to the point of fracture - in particular the effects of fatigue.