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Fatigue mechanisms of thermoplastics
Author(s) -
Riddell M. N.,
Koo G. P.,
O'Toole J. L.
Publication year - 1966
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.760060414
Subject(s) - materials science , thermosetting polymer , composite material , cyclic stress , epoxy , crystallinity , stress (linguistics) , hysteresis , fatigue limit , polyester , mechanism (biology) , philosophy , linguistics , physics , epistemology , quantum mechanics
Failure in fatigue by the mechanism of crack initiation and propagation originationg at flaws and stress concentrations has been fairly well established. It explains the fatigue phenomena in highly elastic materials, namely metals and certain thermosetting plastics such as reinforced polyester and epoxy resins. We have found, however, that a different mechanism dominates the fatigue behavior of thermoplastics. Specifically, the mechanism involves the generationa of heat within the material due to viscous damping or hysteresis. This paper presents fatigue, damping data and temperature measurements during cyclic stress to support this conclusion on three themoplastic resins of widely different mechanical properties, polyetrafluouoethylene (PTFE), Nylon 6, and polymethyl‐methacrylate (PMMA). In addition to the usual S‐N fatigue curves, we wil show how surface temperature changes with fatigue life and how this change is affected by stress, Frequency, crystallinity, specimen geometry and other parameters. Alos, the loss compliance of the materials will be presented as afunction of temperature to show the relationship of fatigue to damping properties.