SYMPOSIA PAPER Published: 01 January 1979
STP36933S

Load History-Edge Damage Studies in Two Quasi-lsotropic Graphite Epoxy Laminates

Source

The purpose of this investigation was to observe and document the details of edge damage initiation, growth, and interaction as a function of load history and determine the effect of the damage state on material properties. Quasi-isotropic graphite/epoxy specimens with two different stacking sequences were selected to study the damage behavior under both tensile and compressive out-of-plane normal stresses. Observations were made using a replication technique which allows for recording the damage detail along the edge of the stressed specimen.

Specimens were tested in tension-tension fatigue (R = 0.1) at maximum stresses of 234, 290, and 393 MPa (34, 42, and 57 ksi). At selected intervals between 1/2 and 104 cycles, replicas of the edge damage were made. A chronological order of damage events was established for each cyclic stress level and type of laminate. Micromechanical damage in the form of transverse cracks and delaminations initiated at stresses below the proportional limit on the static stress-strain curve and increased with additional cyclic loading in a manner dependent upon the type of laminate. A stable crack density was measured which was dependent on the type of laminate but not on the cyclic stress level. The fracture modes of each laminate were also different. Residual strength and stiffness data are also reported.

Author Information

Stalnaker, DO
Central Research Laboratories, Firestone Tire and Rubber Company, Akron, Ohio
Stinchcomb, WW
Central Research Laboratories, Firestone Tire and Rubber Company, Akron, Ohio
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Details
Developed by Committee: D30
Pages: 620–641
DOI: 10.1520/STP36933S
ISBN-EB: 978-0-8031-4743-0
ISBN-13: 978-0-8031-4495-8