Finite Element Modeling of Fatigue in Fiber–Metal Laminates

Innovative hybrid materials developed at Delft University of Technology (e.g., ARALL and GLARE) dramatically reduce life-cycle costs and offer a great opportunity for service life extension of legacy aircraft. Replacement or repair of damaged aircraft components requires high-strength composite materials with high tailorability, fatigue, and impact-damage resistance, all of which are offered by the advanced hybrid materials. In addition, a reliable fatigue-life evaluation methodology for hybrid structures of arbitrary layup, configuration, constituent materials, and geometry is necessary. An efficient computational framework is presented for simulation of fatigue fracture in fiber–metal laminates based on the homogenized laminate modeled with large shell elements and cohesive zone used to simulate crack propagation. The cohesive traction–separation relationship is calibrated against the analytical solution for the strain-energy release rate, which explicitly accounts for the effect of fiber bridging. Appropriate calibration of the cohesive energy results in approximately constant crack-growth rate, a characteristic for fiber–metal laminates, as well as an accurate distribution of bridging stresses for the considered crack and delamination configurations. The proposed methodology is illustrated by simulating an experimental test conducted on a large glass-laminate-aluminum-reinforced-epoxy panel subjected to a constant-amplitude fatigue loading.