Progress in non-destructive 3D characterization and modelling of aerospace composites

The route to lighter composite aerostructures requires advanced 3D non-destructive characterization methods to provide confidence that the as-built structures conform to the design expectations. Whilst X-ray Micro-CT imaging is an excellent non-destructive testing (NDT) method for 3D characterization, it can rarely be applied in production. In its place, ultrasound is an ideal vehicle for exploring the detailed local response of a composite structure, providing data that can be inverted to give 3D fiber direction, ply spacing, fiber volume fraction and 3D porosity distribution. The first material property that must be determined to enable full characterization and materials modelling of as-manufactured composite components is the vector field representing the fiber direction at every point. Inversion methods have been developed for converting 3D NDT data sets into 3D profiles of material properties. A study of ultrasonic analytic-signal propagation in composites has resulted in a novel method for tracking plies and ply drops, in ultrasonic full-waveform data sets. This paper presents methods for tracking the 3D orientation of fiber tows in the plies throughout a laminated composite structure and examples of finite-element models built directly from this NDT information.