Measurements of the Stress Supported by the Crush Zone in Open Hole Composite Laminates Loaded in Compression

Abstract

Compression failures in composite laminates containing circular holes are often preceded by the development of a damage zone which grows with increasing compressive load. This damage zone which appears similar to a flat, tension fatigue crack in metals, initiates at the edges of the hole and propagates across the width of the laminates leading to final failure. The damage zone is initiated by local fiber buckling and/or shear crippling in the edges of the hole. The length or size of the damage zone increases with increasing load, propagating until the zone completely traverses the specimen. Subsequently, a more catastrophic failure occurs giving brooming and/or delamination. Measurements of the load supported by the damage zone were made, allowing a more realistic constitutive rela tionship to be defined for the composite material in the crush zone.

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References

Guynn, E.G. , W.L. Bradley and W. Elber. "Micromechanics of Compression Failures in Open Hole Composite Laminates," ASTM 2nd Symposium on Composite Materials: Fatigue and Fracture, Cincinnati, Ohio (April 27-30, 1987).

Guynn, E.G. "Micromechanics of Compression Failures in Open Hole Composite Laminates ," Department of Mechanical Engineering, Texas A&M University, M.S. Thesis (December, 1987).

Aronsson, C.G. and J. Backlund. "Tensile Fracture of Laminates with Cracks," J. Composite Materials, 20:287-307 (May, 1986).

Aronsson, C.G. and J. Bäcklund. "Tensile Fracture of Laminates with Holes," J. Composite Materials, 20:259-286 (May, 1986).

Barenblatt, G.I. "The Mathematical Theory of Equilibrium Cracks in Brittle Fracture," Advance in Applied Mechanics, 7:55-129 (1960).

Newman, J.C., Jr. "A Nonlinear Fracture Mechanics Approach to the Growth of Small Cracks ," Behavior of Short Cracks on Airframe Components, AGARD Conference Proceedings, Neuilly Sur Seme, France (1982).

Hartness, J.T. "Polyether Matrix Composites," SAMPE Quarterly, pp. 33-36 (January, 1983).

Starnes, J.H. and J.G. Williams. "Failure Characteristics of Graphite/Epoxy Structural Components Loaded in Compression," in Mechanics of Composite Materials—Recent Advances. Z. Hashm and C. T. Herakovich , eds. Pergamon Press , pp. 283-306 (1982).

American Cyanamid Company, Wayne, New Jersey, Engineering Materials Department , "CYCOM HST-7 Tough Advanced Composites, a 350° Cure High Toughness Epoxy Laminating Material," trade name material description (1986).

10.

Johnston, N. Private communications (April, 1987).

11.

Chan, W. Private commumcations (June, 1987).

12.

Guynn, E.G. and W.L. Bradley. "A Detailed Investigation of the Micromechanisms of Compressive Failure in Open Hole Composite Laminates," to appear in J. of Composite Materials.