Simulation of ultrasonic inspection of composite using bulk waves: Application to curved components

The increasing use of composite materials in aircraft, particularly carbon-fiber reinforced samples, presents new challenges for Non-Destructive Testing (NDT) operations to ensure reliable inspections. The aircraft industry is showing a growing interest in the simulation of NDT techniques applied to such materials, which exhibit strong anisotropy. Simulation tools are needed to predict beam deviations that may arise for curved or tilted parts in complex specimen. A main issue is the modelling of the wave propagation and flaw scattering inside a homogeneous medium considering a continuously variable anisotropic orientation. Previous works have presented a way to model these media. This method consists in decomposing them into a set of homogeneous sub-sections with constant orientations. This approximation allows us to use straight paths over homogeneous sections but the main drawback is that it introduces artificial boundaries leading to numerical instabilities. The new model deals with a continuously variable anisotropy. It is based on a ray calculation for an inhomogeneous medium using an iterative time-step method. This method consists in solving for each time step a system of differential equations taking into account the continuous anisotropic orientation variation along the trajectory.