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Measure of displacement around holes in composite plates subjected to quasi-static compressionContour maps of thickness changes were obtained for three quasi-isotropic graphite-epoxy plates with central holes, loaded in compression. Thickness changes were determined for six load increments from nearly zero to within a few percent of the failure load. The largest change of thickness occurred near the hole but not at the boundary of the hole. Below 90 percent of the failure load, the thickness changes were nearly proportional to load. Irregularities of thickness changes occurred in zones of compressive stresses and they were attributed to localized fiber buckling. A new optical technique was developed to measure thickness changes with high sensitivity. It utilizes a comparatively simple means of holographic interferometry on both sides of the specimen, followed by additive moire to obtain thickness changes as the sum of the out-of-plane displacements. Sensitivity was 12.5 x 10 to the -6 power in. per fringe order. The fringe patterns represent thickness changes uniquely, even when specimen warpage and consequent out-of-plane displacements are very large.
Document ID
19860016905
Acquisition Source
Legacy CDMS
Document Type
Contractor Report (CR)
Authors
Duke, J. C., Jr. (Virginia Polytechnic Inst. and State Univ. Blacksburg, VA, United States)
Post, D. (Virginia Polytechnic Inst. and State Univ. Blacksburg, VA, United States)
Czarnek, R. (Virginia Polytechnic Inst. and State Univ. Blacksburg, VA, United States)
Asundi, A. (Virginia Polytechnic Inst. and State Univ. Blacksburg, VA, United States)
Date Acquired
September 5, 2013
Publication Date
June 1, 1986
Subject Category
Composite Materials
Report/Patent Number
NASA-CR-3989
NAS 1.26:3989
Accession Number
86N26377
Funding Number(s)
PROJECT: RTOP 505-63-11-03
CONTRACT_GRANT: NAG1-193
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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