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Journal of Materials Science

, Volume 18, Issue 3, pp 687–702 | Cite as

A mechanism of crack branching in polymethyl methacrylate and the origin of the bands on the surfaces of fracture

  • Michael J. Doyle
Papers

Abstract

At low crack velocities the fracture of high molecular weight polymethyl methacrylate occurs by the separation of a thin craze layer ahead of, and coplanar with, the propagating crack tip. Above some critical velocity, about 400 m sec−1 at room temperature, craze branching or bifurcation is initiated. The craze branching does not cause any detectable surface roughening of the fracture surface until the crack tip stress is sufficient to initiate cracks in the craze branches. At this stage the formation of the branching craze-cracks causes surface roughening (bands or striations), a deceleration of the main fracture and a drop in the stress amplitude around the crack tip which is below that necessary to initiate branching crazes. The fracture then reverts back to the simpler mechanism, with no surface roughening. The repetition of this process gives rise to the banded appearance of the fracture surface.

Keywords

Polymer Molecular Weight Surface Roughen Fracture Surface High Molecular Weight 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Chapman and Hall Ltd 1983

Authors and Affiliations

  • Michael J. Doyle
    • 1
  1. 1.Department of Mechanical EngineeringUniversity of PittsburghPittsburghUSA

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