Influence of specimen twisting on fracture surface evolution in the split-shear torsion test

Allison L. Johnston, Barry D Davidson

Research output: Contribution to conferencePaperpeer-review

Abstract

The influence of specimen twisting during anti-plane shear (mode III) loading in composite split beam specimens is studied using the split-shear torsion test. Tests were conducted on specimens with different thicknesses and delamination lengths to produce different amounts of specimen twisting prior to fracture. It is shown that specimen twisting causes mode I stresses to develop that are proportional to the angle of twist, thereby producing mixed-mode I-III conditions along the delamination front. This causes near-tip transverse cracks to initiate, prior to delamination advance, at an orientation related to the mode mix, and therefore to the angle of twist. Unlike what occurs in homogeneous materials, it is observed that the laminate's fibers restrict the amount by which these transverse cracks can rotate during extension, and that transverse crack extension is accompanied by planar delamination advance. The overall fracture surface evolution is therefore strongly controlled by specimen and test geometry. The influence of these findings on the apparent delamination toughness as obtained from composite split beam tests, as well as on mode III delamination toughness testing in general, is discussed.

Original languageEnglish (US)
StatePublished - Jan 1 2015
Event20th International Conference on Composite Materials, ICCM 2015 - Copenhagen, Denmark
Duration: Jul 19 2015Jul 24 2015

Other

Other20th International Conference on Composite Materials, ICCM 2015
CountryDenmark
CityCopenhagen
Period7/19/157/24/15

Keywords

  • Delamination
  • Fracture
  • Matrix cracking
  • Mixed-mode
  • Mode III

ASJC Scopus subject areas

  • Engineering(all)
  • Ceramics and Composites

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