Abstract
A multispan quasi-isotropic graphite-PEEK beam exhibited dramatic shear strains in the interlaminar region between plies. Shear strains in the plies themselves varied in basic accord with fiber direction. The large anomalous shear strains were developed near the center of the beam height, where shear stresses were large. High-sensitivity moiré interferometry with 2400l/mm (60,960l/in.) was used. A new technique of data extraction was developed, using carrier fringes to transform the pattern to one in which fringe slopes are proportional to derivatives of displacement. This technique enhanced detection and measurement of highly localized shear-strain gradients.
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References
Post, D., Czarnek, R., Joh, D. and Wood, J., “Deformation Measurements of Composite Multi-Span Beam Shear Specimens by Moiré Interferometry,” NASA Contractor Rep. 3844 (Nov. 1984).
Post, D., “Moiré Interferometry,”SEM Handbook on Experimental Mechanics, ed. A.S. Kobayashi, Prentice-Hall, Englewood Cliffs, NJ, Chap. 7 (1987).
Post, D., “Moiré Interferometry at VPI & SU,”Experimental Mechanics,23 (2),203–210 (June 1983).
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Post, D., Czarnek, R. & Joh, D. Shear strains in a graphite/PEEK beam by moiré interferometry with carrier fringes. Experimental Mechanics 27, 246–249 (1987). https://doi.org/10.1007/BF02318089
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DOI: https://doi.org/10.1007/BF02318089