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An investigation of brittle failure in ductile, notch‐sensitive thermoplastics
Author(s) -
Nimmer Ronald P.,
Woods Joseph T.
Publication year - 1992
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.760321610
Subject(s) - crazing , brittleness , materials science , composite material , polyetherimide , polycarbonate , stress (linguistics) , amorphous solid , environmental stress cracking , brittle fracture , catastrophic failure , fracture (geology) , forensic engineering , polymer , philosophy , linguistics , chemistry , organic chemistry , alloy , stress corrosion cracking , engineering
Brittle failure, a significant design issue for plastic components subject to impact loads, is especially catastrophic when the material is normally ductile. Such behavior is not adequately understood relative to the micromechanisms, controlling parameters, and design consequences in plastics. Previous work has identified the process of crazing as being relevant to these failures in thermoplastics. The relationship between crazes generated through mechanical loading and subsequent brittle failure of amorphous thermoplastics is discussed and the hypothesis that the craze event is a necessary but insufficient condition for brittle failure is employed. Emphasis is focused upon the engineering prediction of craze formation and its use as a conservative brittle failure criteria for defining geometric details to prevent brittle failure. First, a series of experiments using one geometry is applied to study the concept of crazing as a precursor to brittle fracture in the two amorphous polymers polycarbonate and polyetherimide. Second, three‐dimensional finite element analyses are used to assess the effects of changes in geometric detail upon the continuum stress state and eventual failure of the specimen for these two materials.