Abstract
Fatigue cracked primary aircraft structural parts that cannot be replaced need to be repaired by other means. A structurally efficient repair method is to use adhesively bonded patches as reinforcements. This paper considers optimal design of such patches by minimizing the crack extension energy release rate. A new topology optimization method using this objective is developed as an extension of the standard SIMP compliance optimization method. The method is applied to a cracked test specimen that resembles what could be found in a real fuselage and the results show that an optimized adhesively bonded repair patch effectively reduces the crack energy release rate.
Highlights
The development of the topology optimization method described in this paper is driven by a clear practical application, namely the repair of aircraft parts containing cracks
If fatigue cracking occurs during service life it is costly and impractical or most often impossible to replace these parts
We present optimal repair patch geometries created by both an essentially standard compliance optimization formulation and the novel formulation that uses the crack energy release rate as objective
Summary
The development of the topology optimization method described in this paper is driven by a clear practical application, namely the repair of aircraft parts containing cracks. Primary load carrying structures in fuselages are mainly manufactured from machined and/or forged single piece parts Such parts are weight optimized and contain most often stress raisers of various kinds, e.g., cut-outs, thickness steps and interacting radii which make them prone to fatigue failure. For the aero structural applications motivating the developments in this paper, except for very short cracks, small scale yielding conditions can be assumed to prevail, meaning that inelastic deformations are restricted to a small regime at the crack front, and that the behavior of the crack is governed by the elastic stress state in the material surrounding this plastic zone, see e.g. Anderson (2017) In such a linear elastic fracture mechanics context, the intensity of the loading as seen from the crack can be described. This will be discussed after introducing a more precise form of K(ρ, )
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