Effect of induced external damage on fatigue life of carbon fiber reinforced (CFC) composite

The various advantages of CFC composite materials have lead to its application in lots of area especially in aerospace industry for structural applications. This paper highlights the effect of external damage and its location on the fatigue life of CFC composites. The introduction of the crack of 1 mm width at an angle of 45° was created on the specimens. All the tests were performed using a computer controlled 250 KN servo-hydraulic test system in load mode at room temperature, on one crack and two crack composite specimens. The fatigue strength degradation was monitored through stiffness measurement, which was done using load displacement data obtained during the fatigue loading. The CFC specimens with one inclined crack at the center and two inclined cracks at ends were subjected to constant amplitude loading for stress ratio R = 0.5. The CFC specimens with one crack showed a significant reduction in fatigue life. The fatigue properties for both cracked specimens were evaluated. Fatigue life for one crack specimen was much lower than the two crack specimen. A considerable reduction in stiffness was also observed for both one crack and two cracks specimen.