Numerical Simulation of Fatigue Crack Growth in A Pre-Cracked Thin Plate Repaired With A FRP Patch

A numerical simulation was performed to study the fatigue behavior of a center pre-cracked thin panel of an aluminum alloy 6061-T6 repaired with a polymer composite patch. The patch consists of a thin separating woven GFRP (glass-fiber-reinforced plastics) ply and load-bearing UD-CFRP (carbon-fiber-reinforced plastics) plies. The model was simulated using the finite element package ANSYS 15.0. The cohesive zone material model (CZM) was employed to simulate the behavior of the interface between the skin and the patch. The numerical model evaluated J-integral for different crack lengths (2a = 20 mm, 22 mm, …., 32 mm). The value of stress intensity factor (\(K_{I}\)) was evaluated for each crack length using equivalence relation between the J-integral and \(K_{I}\). A second-order polynomial curve was fitted to obtain the algebraic relationship between \(\Delta K_{I}\) and crack length. The Paris law was invoked to get the relation between the crack growth and the number of cycles. The relationship, predicted by the numerical simulation, matched well with those obtained from experimental studies.