Stacking sequence effect on local delamination onset in fatigue

Conference · Fri Dec 31 04:00:00 EST 1993

OSTI ID:143564

O`Brien, T K ^[1]

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1. NASA Langley Research Center, Hampton, VA (United States)

The influence of stacking sequence on local delamination onset from angle ply matrix cracks was studied. Constant amplitude, tension-tension fatigue tests were conducted at a frequency of 5 Hz and an R-ratio of 0.1 on ({theta}{sub 2}/{minus}{theta}{sub 2}/O{sub 2}){sub s} AS4/3501-6 graphite/epoxy laminates where {theta}was 15 or 30 degrees. Dye penetrant enhanced radiography was used to document the onset of matrix cracking and the subsequent onset of local delaminations. The onset of local delaminations in fatigue for the ({theta}{sub 2}/{minus}{theta}{sub 2}/O{sub 2}){sub s} layups tested in this study where compared with results for (O{sub 2}/{theta}{sub 2}/{minus}{theta}{sub 2}){sub s} layups tested previously. The maximum cyclic load versus the number of cycles to local delamination onset for the two layups was quite different. A strain energy release rate, G, solution for local delamination growing from an angle ply matrix crack was used to characterize these local delaminations and identify the fracture mode dependence. The need for detailed analyses of the delamination fracture modes and mixed-mode delamination fatigue onset criteria was demonstrated.

• OSTI ID: 143564
• Report Number(s): CONF-930246--; ISBN 0-87339-251-5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
FATIGUE
FRACTURE PROPERTIES
GRAPHITE
MECHANICAL PROPERTIES
STATIC LOADS