Non-destructive inspection of composite structures using modal analysis

Abstract

Anomalies from manufacturing variability or in-service damage are manifested as subtle differences in the inertial and stiffness matrices of otherwise identical components. Modal analysis seeks to model these constitutive relations by examining a structure's dynamic response to applied vibrations. In this investigation, characterization of anomalies in composite structures is attempted through multi-input, multi-output modal analysis. Two graphite-epoxy specimens manufactured by different processes are subjected to random excitation and frequency response functions are obtained. The dynamic behavior of the structures is compared through modal parameter extraction techniques. Dynamic solutions from a finite element model are used to validate the results. Finally, observations are made concerning the feasibility of extending the procedure to quality assurance and damage detection applications. (MM)