Wave propagation in thin pretwisted composite strips with an embedded delamination

Abstract

In this work, a thin pretwisted and delaminated composite strip is modeled using the variational asymptotic method (VAM). The original 3D problem is reduced to a 2D cross-sectional analysis and a 1D problem along the length of the strip. Damage, in the form of an embedded delamination, is accounted in the strip by following a sublaminate approach. The 1D governing elastodynamic equations of the strip model is solved using the spectral finite element (SFE) method, wherein the structure is modeled as a wave guide. In SFE method, the governing elastodynamic equations are solved in transformed frequency domain to obtain the dynamic stiffness matrix. The guided wave response of the delaminated composite structure for different loads and boundary conditions are subsequently computed. Modal and wave response from SFE using the reduced 1D model are validated by comparing results with those reported in the literature and in some cases with the results obtained from a 3D model using a direct finite element (FE) package. Modal and wave propagation analysis is performed for various dimensions of delamination and composite layup. The analysis provides insight into the dynamic characteristic of partially delaminated strip. The usage of SFE is expected to yield a faster result and lesser computation time than the conventional direct FE method for analyzing and monitoring the delaminated strip exposed to high frequency excitations. Additionally, the capability of the model to investigate the inverse problem of damage detection is demonstrated.