Fatigue Crack Initiation and Early Growth in GLARE 3 Fiber-metal Laminate Subjected to Mixed Tensile and Bending Loading

A special open-hole sheet specimen of GLARE fiber-metal laminate was used to simulate mixed loading similar to the loading of a riveted hole in a real fuselage skin structure. The effect of cyclic tension and secondary bending loading was studied. The notch region was observed through a microscope in order to detect the first fatigue crack initiation during fatigue loading. The number of cycles prior to crack initiation was measured, and the crack growth rate in the surface layer of the laminate was evaluated. The specimens were subjected to fatigue damage investigation in the inner layers of the laminate after termination of the test. A significant effect of secondary bending on fatigue crack initiation and early crack growth was found. The experimental results are discussed in terms of local stress-strain conditions in the notch region evaluated by means of finite element calculation.