Local Delamination In Laminates With Angle Ply Matrix Cracks Part 2 Delamination Fracture Analysis And Fatigue Characterization

Local Delamination in Laminates with Angle Ply Matrix Cracks. Part 2

Constant amplitude tension-tension fatigue tests were conducted on AS4/3501-6 graphite/epoxy (02/ theta sub 2/ -(theta sub 2))sub s laminates, where theta was 15, 20, 25, or 30 degrees. Fatigue tests were conducted at a frequency of 5 Hz and an R-ratio of 0.1. Dye penetrant enhanced x-radiography was used to document the onset of matrix cracking in the central -(theta) degree plies, and the subsequent onset of local delaminations in the theta/ -(theta) interface at the intersection of the matrix cracks and the free edge, as a function of the number of fatigue cycles. Two strain energy release rate solutions for local delamination from matrix cracks were derived: one for a local delamination growing from an angle ply matrix crack with a uniform delamination growing from an angle ply matrix crack with a triangular shaped delamination area that extended only partially into the laminate width from the free edge. Plots of G(max) vs. N were generated to assess the accuracy of these G solutions. The influence of residual thermal and moisture stresses on G were also quantified. However, a detailed analysis of the G components and a mixed-mode fatigue failure criterion for this material may be needed to predict the fatigue behavior of these laminates. Obrien, T. Kevin Langley Research Center...

Local Delamination in Laminates with Angle Ply Matrix Cracks. Part 2: Delamination Fracture Analysis and Fatigue Characterization

Structural Integrity and Durability of Advanced Composites

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