Strain and failure analysis of graphite/epoxy plates with cracks - Experimental-stress-analysis techniques were used to study the deformation and failure of uniaxially loaded graphite/epoxy plates with cracks and the effect of notch size was analyzed

Isaac M. Daniel*

*Corresponding author for this work

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28 Scopus citations

Abstract

The objective of this investigation was to study the deformation and failure of uniaxially loaded graphite/epoxy plates with cracks and to determine the influence of notch size on failure. The specimens were quasi-isotropic laminates with cracks of various lengths. They were instrumented with strain gages, photoelastic coatings and moiré grids. Strains near the crack tip show two distinct points of rate change at strain levels of 0.002 and 0.006, the latter corresponding to the ultimate strain of the 90-deg plies. Failure near the crack tip takes the form of a damage zone consisting of ply subcracking along fibers, local delamination and fiber breakage. Failure occurs when this damage zone reaches some critical value. Measured maximum strains at failure exceeded twice the ultimate strain of the unnotched laminate. The average stress over a characteristic distance (5 mm) from the crack tip was used as a criterion to describe the influence of crack length on failure. Comparison of results with those from similar specimens with circular holes showed that strength was nearly independent of notch geometry in this case, i.e., specimens with holes and cracks of the same size had nearly the same strength.

Original languageEnglish (US)
Pages (from-to)246-252
Number of pages7
JournalExperimental Mechanics
Volume18
Issue number7
DOIs
StatePublished - Jul 1 1978

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering

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