Composite Materials

· For a uniaxial carbon-fiber epoxy matrix system, the fatigue response is different in tension and compression as shown.
· Fiber buckling in the compression testing mode gives rise to fiber-matrix debonding, matrix shear failure, and longitudinal splitting of the composite.
· To obtain a given fatigue life in compression cycling (with zero minimum stress), the stress amplitude had to be kept to about half that which would give the same fatigue life in tensile cycling.

From: Hertzberg & Mason, "Fatigue of Engineering Plastics," Academic Press (1980)