Plastic Deformation, Crazing, and Fracture Morphology of Acrylic Fibers1

Morphology and tensile properties of acrylic fibers with different manufacturing histories have been investigated. Acrylic fibers that have been partially drawn undergo appreciable plastic deformation after passing through a yield point and exhibit "crazing" over the entire surface. On the other hand, acrylic fibers that have been fully drawn and annealed display no yield point or crazing and have a lower modulus and con siderably reduced elongation-to-break. SEM photomicrographs of tensile fractures in dicate that the former acrylic fibers show a straight fracture along a transverse section, while the latter invariably fail by axial splitting. The morphological structure of acrylic fibers develops and is perfected as a consequence of the manufacturing process, which alters the fibers' response to applied tensile stress.