Accession Number : ADA304605

Title :   Deformation Measurements of Composite Multi-Span Beam Shear Specimens by Moire Interferometry.

Descriptive Note : Final rept.,

Corporate Author : VIRGINIA POLYTECHNIC INST AND STATE UNIV BLACKSBURG

Personal Author(s) : Post, Daniel ; Czarnek, Robert ; Joh, Duksung ; Wood, Judy

PDF Url : ADA304605

Report Date : NOV 1984

Pagination or Media Count : 99

Abstract : Experimental analyses were performed for determination of in-plane deformations and shear strains in unidirectional and quasi-isotropic graphite epoxy beams. Forty-eight-ply beams were subjected to 5-point and 3-point flexure. Whole field measurements were recorded at load levels from about 20% to more than 90% of failure loads. Contour maps of U and W displacement fields were obtained by moire interferometry, using reference gratings of 2400 lines/mm or 60,960 lines/in. Clearly defined fringes with fringe orders exceeding 1000 were obtained. Whole field contour maps of shear strains were obtained by a method developed for these tests. Various anomalous effects were detected in the displacement fields. Their analysis indicated excess shear strains in resin rich zones in regions of shear tractions; free edge shear strains in quasi-isotropic specimens in regions of normal stresses; and shear stresses associated with cyclic shear compliances of quasi-isotropic plies in regions of shear tractions. Their contributions could occur independently or in superposition. Qualitative analyses addressed questions of relaxation; influence of contact stress distribution; specimen failure; effect of specimen overhang; nonlinearity; and qualities of 5- and 3-point flexure tests.

Descriptors :   *BEAMS(STRUCTURAL), *DEFORMATION, *INTERFEROMETRY, *SHEAR STRESSES, *MOIRE EFFECTS, ANOMALIES, FIELD TESTS, GRATINGS(SPECTRA), NONLINEAR SYSTEMS, TRACTION, MAPS, GRAPHITE EPOXY COMPOSITES, CONTOURS.

Subject Categories : Mechanics
      Structural Engineering and Building Technology

Distribution Statement : APPROVED FOR PUBLIC RELEASE