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This paper details the analytical and experimental work required to predict delamination onset and growth in a curved cross-plied composite laminate subjected to static and fatigue loads. The composite used was AS4/3501-6, graphite/epoxy. Analytically, a closed-form stress analysis and 2-D and 3-D finite element analyses were conducted to determine the stress distribution in an undamaged curved laminate. The finite element analysis was also used to determine values of strain energy release rate at a delamination emanating from a matrix crack in a 90° ply. Experimentally, transverse tensile strength and fatigue life were determined from flat 90° coupons. The interlaminar tensile strength and fatigue life were determined from unidirectional curved laminates. Also, Mode I fatigue and fracture toughness data were determined from double cantilever beam specimens. Crossplied curved laminates were tested statically and in fatigue to give a comparison to the analytical predictions. A comparison of the fracture mechanics life prediction technique and the strength-based prediction technique is given. Generally, both prediction techniques gave good comparisons with the experimental results.
composite material, delamination, curved laminate, strain energy release rate, fracture toughness, matrix crack
Analytical Services and Materials, Inc., MS 188E, NASA Langley Research Center, Hampton, Virginia
U.S. Army Aerostructures Directorate, MS 188E, NASA Langley Research Center, Hampton, Virginia