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Locating Delaminations in Composite Beams Using Gradient Techniques and a Genetic Algorithm

2001; American Institute of Aeronautics and Astronautics; Volume: 39; Issue: 7 Linguagem: Inglês

10.2514/2.1457

1533-385X

Christopher Harrison, Richard Butler,

Structural Engineering and Vibration Analysis

This paper presents a method of locating delaminations within composite beams. The method compares the experimental natural frequencies and mode-shapes of a delaminated beam, with those predicted by an analytical model. The differences are quantified by an objective function, which is minimised using a numerical optimisation technique. When the difference between the analytically produced modal parameters, and those measured experimentally, is minimised, the damage is said to have been located. A simple model, based on the static deflection of a cantilever beam, is developed to obtain an estimate for the effective shear rigidity of the delaminated area, and this is incorporated into the Dynamic Stiffness Method (DSM). The damage is located using a two stage optimisation process. Firstly the differences in the analytical and experimental frequencies and modeshapes are minimised by altering the material properties and boundary conditions of the model. Once the differences have been minimised for an undamaged beam, damage is located by altering the number, size and location of delaminations within the beams. Results are obtained and compared using two different optimisation procedures; a gradientbased optimisation procedure and a genetic algorithm.