Effects of Delamination on the Vibration Charecteristics of Composite Beams

Abstract

Development of an early damage detection method for delamination is one of the most important keys in maintaining the integrity and safety of composite structures. The present study focuses on the effects of delamination on the vibration characteristics of beams with single through-width delamination. Comparison is made between experimental study on aluminum specimens and corresponding finite element models created in ANSYS using brick elements. Specimens are made by bonding thin aluminum strips using very thin adhesive layers, with delaminations introduced by inserting cellophane paper at pre-determined locations. Vibration tests are carried out on the specimens, the results of which are compared with those of the finite element analysis. The finite element model was then used to demonstrate the comparison of natural frequency, mode shapes and curvature mode shapes of the intact and delaminated models. Further, the analysis is extended into layered composites of orthotropic materials. Comparisons are made between published experimental results of laminates and results of finite element analyses on models with layered brick elements using ANSYS. Eigen value extraction was done on ‘free’ models, with no constrains between the delaminated layers and models with linear spring connecting the delaminated layers.