ISSN:
0021-8995
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
Crazing in styrene-acrylonitrile copolymer (SAN) under a triaxial stress state was examined. The damage zone that formed ahead of a semicircular notch under slow tensile loading consisted of two kinds of crazes: internal notch crazes that grew out from the notch root and discontinuous surface crazes. Examination of the damage zone in the optical and scanning electron microscopes revealed that the internal notch crazes sometimes extended through most of the thickness but never penetrated the free surfaces, whereas the surface crazes penetrated about 10-50 μm inward from the surface. Initially, the internal craze tips defined a crescent-shaped zone. The plane strain elastic stress distribution at the zone boundary satisfied a constant mean stress condition, and the critical mean stress for craze tip growth was determined to be about 35 MPa. This value varied slightly for different resins but was independent of thickness. Propagation of the internal notch crazes occurred in a straight line parallel to the minor principal stress vector at the point of origin on the notch surface, whereas the surface crazes followed the minor principal stress trajectories. The presence of the internal notch crazes resulted in significant stress redistribution, the stress redistribution was described quantitatively using both the deviation of the craze trajectory from the minor principal stress trajectory, and the deviation of the zone shape from the critical elastic mean stress condition.
Additional Material:
18 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/app.1992.070460203
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