Microstructural aspects of the fatigue crack growth in polypropylene and its chopped glass fiber reinforced composites

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Abstract

Fatigue crack propagation (FCP) behaviour of injection-molded neat polypropylene (PP) and its short (SGF) and long glass fiber (LGF) reinforced composites with 10–40 wt. % GF content was investigated at ambient temperature on notched compact tension (CT) specimens in tension-tension mode. It was established that the FCP response both of the the neat and reinforced PP highly depended on the related microstructure. Resistance to FCP of the matrix increased with increasing molecular mass and, in addition, it was affected by morphological rearrangements in the skin-shear-core structure caused by molding. Incorporation of GF reduced the FCP rate considerably; this effect became more pronounced at a higher aspect ratio of the fiber. Stable acceleration in FCP, described by the Paris power law, was preceded by a deceleration range. This stable delayed crack growth was connected with a crack tip blunting process due to morphological changes in the neat PP. This range appeared also in composites due to development “stabilization” of a characteristic damage zone according to microscopic results. Effects of the microstructure on the FCP response of both matrix and composites were summarized schematically, too. Paris type description seemed to be adequate for composites with a matrix of low molecular mass and good fiber/matrix interfacial adhesion. Poor bond quality and/or use of matrices with high molecular mass or toughening necessitates FCP description by the crack layer theory.

Original languageEnglish
Pages (from-to)97-122
Number of pages26
JournalJournal of Polymer Engineering
Volume10
Issue number1-3
DOIs
Publication statusPublished - Mar 1991

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Polymers and Plastics
  • Materials Chemistry

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