Fatigue crack propagation mechanisms in poly(methyl methacrylate) by in situ observation with a scanning laser microscope

C. Ishiyama, T. Asai, M. Kobayashi, M. Shimojo, Y. Higo

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Crack propagation tests were performed on an amorphous polymer, poly-(methyl methacrylate), to investigate fatigue crack propagation mechanisms. A scanning laser microscope with a newly developed tensile testing machine was used to observe in situ crack propagation in compact-type specimens. A crack usually propagated within the craze located at the crack tip under both static and cyclic loading conditions. When a crack stably propagated into the craze under static loading conditions, bright bands composed of the broken craze were observed at the edges along the crack wakes. However, there were successive ridges and valleys in place of bright bands along the crack wakes under cyclic loading conditions. When stable fatigue cracks were propagated at the loading half-cycle in each cycle, new craze fragments appeared that were similar to the bright bands under static loading. However, the thickness of these fragments decreased in the following loading cycle, and a new valley was formed. This suggested that the valleys were formed by the contact between the fracture surfaces near the crack tip during unloading. Fatigue crack propagation is thought to be due to fibrils weakened by crack closure between fracture surfaces.

Original languageEnglish
Pages (from-to)3103-3113
Number of pages11
JournalJournal of Polymer Science, Part B: Polymer Physics
Volume39
Issue number24
DOIs
Publication statusPublished - 2001 Dec 15

    Fingerprint

Keywords

  • Amorphous
  • Crazing
  • Fatigue crack growth
  • Fracture
  • In situ observation
  • Poly(methyl methacrylate)
  • Scanning laser microscope
  • Striations

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Materials Chemistry

Cite this