Investigation of damage effect on the effective dynamic mechanical properties of an adhesive in linear and nonlinear response regimes

Abstract

In this paper, the effect of damage on the effective dynamic Young's and shear moduli of a viscoelastic adhesive is investigated, in both linear and nonlinear regions of adhesive behavior. The investigation method is based on the measurement of the nonlinear Frequency Response Function (FRF) of adhesive bonded structure and inverse eigen sensitivity identification technique. Several single-lap joint specimens are manufactured in healthy and damaged configurations and their linear and nonlinear FRFs are then measured, using the Optimum Equivalent Linear FRF (OELF) concept. The measured FRFs are then used to extract linear and nonlinear bending and shear modes of the bonded structure. The modes of healthy and damaged structures are further used for identifying of Young's and shear moduli at different frequencies. The results show that, for both linear and nonlinear regions, damages as small as 5% in the adhesive joint can be detected by the proposed technique, through their effects on the identified effective mechanical properties.