Biaxial testing of [O2/±45]s graphite/epoxy plates with holes - Deformation and failure of [O2/±45]s graphite/epoxy plates with holes under biaxial tension were studied experimentally and the influence of hole diameter on failure was determined

Isaac M. Daniel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

An experimental investigation was conducted to study the behavior under biaxial-tensile loading of [O2/±45]s graphite/epoxy plates with circular holes and to determine the influence of hole diameter on failure. The specimens were 40-cm×40-cm (16-in.×16-in.) graphite/epoxy plates of [O2/±45]s layup. Four hole diameters, 2.54 cm (1.00 in.), 1.91 cm (0.75 in.), 1.27 cm (0.50 in.) and 0.64 cm (0.25 in.), were investigated. Deformations and strains were measured using strain gages and birefringent coatings. Biaxial tension in a 2:1 ratio was applied by means of four whiffle-tree grip linkages and controlled with a servohydraulic system. Stress and strain redistributions occur around the hole at a stress level corresponding to localized failure around the 67.5-deg location and nonlinear strain response at the 0-deg location. Maximum measured strains at failure on the hole boundary are higher (approximately 0.016) than the highest ultimate strain of the unnotched laminate (0.010). Two basic patterns of failure were observed: (a) horizontal cracking initiating at points off the horizontal axis and accompanied by extensive delamination of the subsurface ±45 deg plies, and (b) vertical cracking along vertical tangents to the hole and accompanied by delamination of the outer 0-deg plies. The strength reduction ratios are lower than corresponding values for uniaxial loading by approximately 16 percent, although the stress-concentration factor under biaxial loading is lower.

Original languageEnglish (US)
Pages (from-to)188-195
Number of pages8
JournalExperimental Mechanics
Volume22
Issue number5
DOIs
StatePublished - May 1 1982

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering

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