Analytical and Numerical Study of Local Defect Resonance Frequencies in Fibre Metal Laminates

Abstract

The recent developments in the field of nonlinear wave spectroscopy is found to be very effective in diagnosing complicated defects in modern structures due to its enhanced resolution and accuracy compared to its counterparts. Local defect resonance (LDR) is one of such method which is based on intensifying the vibrations at the contacting surfaces. This method is found to be very efficient in early detection of cracks or any flaws in the material. In the present work, nonlinear vibration response of a fibre metal laminate (FML) having a circular delamination is studied in order to determine its local defect resonance frequency. The concept of LDR has been provided analytically and is validated using linear steady state analysis of Glass Reinforced Aluminium (GLARE) model in ABAQUS 6.13 software. Moreover, the nonlinearities caused due to intermodulation and interaction terms are observed by performing explicit dynamic analysis at LDR, super harmonic and sub harmonic frequencies. The explicit dynamic analysis is performed by considering four different forcing frequencies in form of continuous periodic excitation. It was evident that the effect of these excitations can be seen from any point on the GLARE model, independent of its location. Subsequently, the proposed study is validated by considering two different locations of the delamination in the GLARE model. The results obtained from the present study will be of high importance in performing structural health monitoring and high resolution imaging of defects in fibre metal laminates.