Deformation Measurements of Composite Multi-Span Beam Shear Specimens by Moire Interferometry.
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1984
- Accession Number
- ADA304605
Entities
People
- Daniel Post
- Duksung Joh
- Judy Wood
- Robert Czarnek
Organizations
- Virginia Tech