ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
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:
Earlier studies of fatigue crack propagation (FCP) in polymers have shown a general superiority of crystalline relative to amorphous polymers in terms of FCP resistance. In order to study in detail the effect of crystalline content and character on FCP rates, poly(ethylene terephthalate) (PET) was selected as a convenient material in which a wide range of crystallinity can be obtained. To provide a baseline for comparison, FCP rates were determined for essentially amorphous polymers covering a range of molecular weight. Surprisingly, the essentially amorphous PET turned out to be as resistant to FCP as the best crystalline polymers so far observed. In this paper, several observations about FCP rates and fracture topography are reported: FCP rates agree well with the Paris equation over a wide range of ΔK; in any case, the higher the molecular weight, the greater the crack growth resistance according to the Manson-Hertzberg relationship previously established. Fracture surface analysis revealed evidence of softening and drawing, as well as extensive plastic deformation. We suggest that PET can undergo, under cycling loading, both extensive drawing and actual crystallization at the crack tip to form an efficient, crack-resistant network. Thus, PET appears to be the first thermoplastic observed to be self-reinforcing in fatigue.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760221512
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