Analysis of Wave Propagation in Rib-Stiffened and Isogrid Panels for Structural Health Monitoring

Abstract

Practical satellites used for commercial and defense applications are very complex. Simplified approximations to satellite panels and components will yield undesirable errors in many damage identification techniques, particularly those that consider time of flight for elastic waves. Rib-stiffened and isogrid panels are such examples of structural satellite components. Preliminary evaluations of health monitoring techniques which relied on a simple flat plate assumption revealed unsatisfactory results for analysis of rib-stiffened structures. Further investigations have been made into the effect which ribs have on wave propagation. A testbed structure was fabricated to include several characteristics of a realistic satellite, including a skeletal structure with isogrid panels secured by threaded fasteners. Several wave propagation runs were taken on the structure through various ribbed paths. Finite element models were developed to explore the nature of waves passing through ribs in both 2D and 3D representations. The investigation resulted in identification of converted wave pulses. The work has lead to the proposed „modified group velocity‟ for calculating the distance to damage based on wave pulse time of arrival.