The effect of low-velocity impact on the fatigue life of Sandwich composites

Impact properties and fatigue properties of sandwich composites after impact are addressed. Specifically, the low-velocity impact resistance of carbon fiber faced sandwich composites and how the fatigue life is affected is studied. Two and four layer face sheet carbon fiber sandwich composite samples with foam filled honeycomb core were impacted in a low velocity drop tester at 10, 20, and 30 J with varying masses and velocities of the impactor. After impact the area of damage is determined using ultrasonic techniques. The fatigue life is then determined and compared to the fatigue life of non-impacted samples in a four point bend test. At all impact energies the impactor completely penetrated the front face of the sample. At 20 and 30 J the impactor also penetrated the back face. The 30 J caused a larger penetration area where as the 20 J caused more delamination of the back face. Two different densities of foam were used for the two layer samples. The two layer high density sample failure was changed from in shear for the virgin materials to bending for the impacted samples. This shows that penetrating the top face has an affect on the fatigue properties of the two layer samples. The fatigue life of the four layer and two layer low density samples does not appear to be affected by the impact.