Bonded crack retarders for aircraft integral metallic structures: a sensitivity analysis of design parameters

Abstract

Bonded crack retarders are an efficient and effective solution to the lack of damage tolerance of integral metallic structures. They provide alternative load paths as well as a mean of transferring load from cracked panels and hence slowing down crack propagation. These bonded crack retarders or straps need to be accurately designed in order to efficiently extend the fatigue life of the structure with the minimum weight penalty and cost. Many tests have been carried out to describe the behaviour of bonded crack retarders but due to the complexity of the problem and the high number of interacting factors, the tests required to produces solid design guidelines are simply too many and the cost and time associated too high. On the other hand, a modelling technique has been developed to predict the fatigue crack growth life of these reinforced structures and it has been extensively validated against experiments. In this paper, this modelling technique is used to conduct sensitivity studies and produce design guidelines for an efficient use of bonded crack retarders on realistic aircraft structures.