Inversion of the shape of defects in composite plates

Defect detection of laminated composite plates using ultrasonic guided waves is of great interest nowadays. Nevertheless, it is still a challenging problem to reconstruct the true shape of defects in anisotropic materials. The inverse method proposed in this paper can directly reconstruct the specific shape of defects. Moreover, this method does not need iteration, is simple in form and easy to use. A three-step strategy of this method is performed as follows: Firstly, based on boundary integral equation and Born approximation assumption, flaw shape function and reflection coefficients form a set of Fourier transform pairs; Secondly, we propose an efficient way to quickly obtain Green’s function and bring it to step 1. Finally, the actual shape and location of flaws can be inversely reconstructed by reflection coefficients in the whole frequency domain obtained by modified boundary element method (BEM). This method is implemented to reconstruct cavity-type flaws at the interface in a laminated composite plate. The correctness and effectiveness of the proposed method is finally validated for several benchmark problems, and the effect of frequency range, flaw size and mode selection on accuracy of the inverse reconstruction are discussed in detail.