Practical Applications of Improvements in Fml Crack Bridging Theory

Fiber metal laminates (FMLs) have excellent crack growth performance compared to monolithic metals thanks to crack bridging by intact fibers in the wake of a fatigue crack. Calculating the distribution of bridging loads in the fibers is key to analyzing and predicting the crack growth of FMLs. Most analytical approaches to modelling this phenomenon do so by imposing compatibility between the deformation of cracked metal layers and the elongation of the bridging fibers. In doing so, they assume that the crack opening displacement is equal to the displacement of the metal sheets at the boundary of the delamination between the cracked and the bridging layers. This paper derives a solution to the crack bridging problem that accounts for the deformation of the metal between the crack flanks and the delamination boundary. The results of doing so show that neglecting that deformation is acceptable for FML crack growth prediction, but the solution incorporating the exact displacement of the metal layers enables the application of the crack bridging method to a variety of additional situations as well as the extension of its applicability to more complex FMLs. This paper surveys a number of such applications, including examples of how to apply crack bridging theory to these problems.