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Effects of the state of stress on the toughness of polycarbonate
Author(s) -
Petrie S. P.,
Dibenedetto A. T.,
Miltz J.
Publication year - 1978
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760181603
Subject(s) - materials science , composite material , toughness , nucleation , polycarbonate , shear band , fracture toughness , residual stress , annealing (glass) , plasticity , chemistry , organic chemistry
It is shown that the mechanical properties of polycarbonate are controlled by the state of stress of the test specimen. Whereas the yield stress of the material is relatively insensitive to the state of stress, the tendency of the material to microcavitate is strongly dependent on the residual stresses in the surfaces of a test specimen. The effects of quenching, annealing, post notching, solvent swelling and rate of testing on the modulus of toughness are all related to the state of compression on the free surfaces. The mechanism of deformation is shown by cinematography to consist of the nucleation of a shear band followed by microcavitation along the propagating band. Maximum toughness is obtained by suppressing microcavitation so as to promote shear yielding. When microcavitation occurs, it is the competition between propagating the microcavitation throughout the material and the generation of microcracks in the advancing shear band that controls the ultimate elongation.