A spectral finite element with embedded delamination for modeling of wave scattering in composite beams

A spectral finite element for modeling of wave scattering in laminated composite beam with embedded delamination is proposed. The method uses fast Fourier transform (FFT) for transformation of the temporal variables into frequency dependent variables and conventional node-based finite element (FE) approach for spatial discretization in frequency domain. The base-laminates and the sub-laminates are treated as structural waveguides, which form the internal spectral elements. The region of delamination is modeled by assuming constant cross-sectional rotation. Equilibrium at the interfaces between the base-laminate and the sub-laminates is imposed using efficient matrix methodology. The internal element nodes are finally condensed to form a single equivalent beam element with embedded delamination and is called damaged spectral element. Only three quantities need to be specified for automated construction of the proposed element. These are the local coordinates of one of the delamination tips and delamination length. The main advantage is the easy insertion of delamination in finite element model and efficient correlation of measured waveforms in structural health monitoring applications. Response predicted by the proposed model has been compared with 2D FE analysis and fairly matching results are found. Sensitivity studies due to parametric variation in delaminated configuration are performed. Methodologies to identify locations and extent of delaminations for structural diagnostics are also highlighted.