Detecting crack size and location in composite rotorcraft flexbeams

Kodanate A. Lakshmanan; Darryll J. Pines

doi:10.1117/12.275665

6 June 1997 Detecting crack size and location in composite rotorcraft flexbeams

Kodanate A. Lakshmanan, Darryll J. Pines

Proceedings Volume 3041, Smart Structures and Materials 1997: Smart Structures and Integrated Systems; (1997) https://doi.org/10.1117/12.275665
Event: Smart Structures and Materials '97, 1997, San Diego, CA, United States

Abstract

The appearance of cracks in composite rotorcraft flexbeams can lead to degradation in flapwise and lagwise performance of the rotor blade. In addition, cracks in composite rotorcraft flexbeams under cyclic loading can result in rapid fatigue failure of these elements. A novel detection strategy is evaluated in this work which attempts to use the dereverberated response to locate damage in the form of a crack. Previous approaches have focused on modal response and damage detection methods. These techniques are incapable of detecting small defects or flaws in structures. However, a continuum mechanics description of the local structural dynamics provides greater resolution in the ability to detect small flaws. This modeling is employed here to determine the location and depth of a crack by examining the frequency domain properties of the scattering coefficient. The phase of this parameter contains properties that capture the size and location of the crack. A least squares optimization is performed to determine both crack depth and location. Analytical predictions are confirmed on an experimental [0/90]s graphite epoxy flexbeam of approximately 16 inches in length. Analytical and experimental results indicate that this approach is able to locate the crack and approximate its depth under centrifugal loading. The model predicts the location within 3% and approximates the depth to within 20%.

Citation Download Citation

Kodanate A. Lakshmanan and Darryll J. Pines "Detecting crack size and location in composite rotorcraft flexbeams", Proc. SPIE 3041, Smart Structures and Materials 1997: Smart Structures and Integrated Systems, (6 June 1997); https://doi.org/10.1117/12.275665

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