SYMPOSIA PAPER Published: 01 January 1986
STP19995S

Influence of Sublaminate Cracks on the Tension Fatigue Behavior of a Graphite/Epoxy Laminate

Source

Quasi-isotropic 32-ply graphite/epoxy specimens were tested in static tension and tension fatigue. Both dry specimens and specimens containing 1% moisture (by weight) were tested. The first type of damage observed under both static and cyclic loading was transverse matrix cracking in the 90-deg plies. Under continued static or cyclic loading the cracks propagated into the neighboring −45-deg plies. No delamination was observed under static loading. In fatigue the matrix cracks acted as initiators of delamination, which resulted in a marked reduction in stiffness and residual strength. For specimens which had been subjected to a tensile overload before fatigue cycling, delamination occurred earlier due to the formation of more transverse matrix cracks.

The major effect of moisture was to increase the stress level at which first-ply failure occurred and to delay damage development during fatigue at low stress levels. The leveling-off of the crack density at an approximately constant level during fatigue loading gives support to damage models which predict the occurrence of a characteristic damage state, independent of load history, before laminate failure.

Author Information

Carlsson, L
Materials, The Aeronautical Research Institute of Sweden (FFA), Bromma, Sweden Center for Composite Materials, University of Delaware, Newark, DE
Eidefeldt, C
The Defence Material Administration, Stockholm, Sweden
Mohlin, T
The Aeronautical Research Institute of Sweden (FFA), Bromma, Sweden Du Pont de Nemours Nordiska AB, Märsta, Sweden
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Details
Developed by Committee: D30
Pages: 361–382
DOI: 10.1520/STP19995S
ISBN-EB: 978-0-8031-4973-1
ISBN-13: 978-0-8031-0470-9