Guided wave based localization and severity assessment of in-plane and out-of-plane fiber waviness in carbon fiber reinforced composites

Waviness is a common geometrical defect in carbon fiber reinforced plastics (CFRP) plates, characterized by local misalignment of an otherwise region of straight fibers. Presence of fiber waviness is a potential source of non-linearity and affects the relative strength of the composite structure. Recently, guided wave (GW) based in situ NDE techniques have been extensively used for damage detection in composite laminates, albeit for damages other than fiber waviness. This work pertains to the numerical investigation of fiber waviness interactions with S0 mode in a bonded composite structure (BCS) panel. The fiber waviness is modeled in curvilinear physics framework in a commercially available finite element (FE) solver, COMSOL Multiphysics. The change in group velocity due to waviness predicted by the FE model developed in this work agrees well with analytical calculations based on change in elastic modulus. This feature is used for localization of fiber waviness region within a network of PZT sensors by utilizing a recently developed damage index (DI) mapping algorithm. The efficacy of DI mapping is demonstrated using noise-augmented FE generated GW data set for a composite panel with a network of lead zirconate titanate (PZT) sensors, for in-plane and out-of-plane fiber waviness with varying severity factors.