Abstract
The objective of this study is to develop an analytical model to predict the fatigue life of aluminum alloy panels repaired by a carbon/epoxy patch. The study includes two parts: an experimental part where fatigue tests were conducted on notched specimens of 2024 T3 and 7075 T6 aluminum alloys repaired by unidirectional carbon/epoxy patches in order to measure the crack propagation rate (da/dN) after bonding of the patch. The second part of the work consists in numerically calculating the stress intensity factor range (ΔK) at the tips of repaired cracks. A fatigue life prediction model was established for repaired plates based on the Paris law. This model relates the Paris constants to the stiffness ratio between the patch and the aluminum plate. The model of fatigue life prediction can be useful for the patch repair designers. The obtained results show that the fatigue life is highly improved by the composite patch specially for the aluminum alloy 2024 T3. The number of cycle at failure increases with the increase of the patch thickness. The stress intensity factor at the crack tip is reduced by the patch repair which leads to a slowdown in the propagation of the crack.