Carbon fiber laminate composites, consisting of layers of polymer matrix reinforced with high strength carbon fibers, are increasingly employed for aerospace structures. They offer advantages for aerospace applications, e.g., good strength to weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Depending on the severity of the impact, delaminations can occur, reducing the load carrying capacity of the structure. Efficient structural health monitoring of composite panels can be achieved using guided ultrasonic waves propagating along the structure. The guided ultrasonic wave (A0 Lamb wave mode) scattering at delaminations was modelled using full three-dimensional Finite Element (FE) simulations. The influence of the delamination size was systematically investigated from a parameter study. The angular dependency of the scattered guided wave amplitude was calculated using a baseline subtraction method. A significant influence of the delamination width on the guided wave scattering was found. The sensitivity of guided waves for the detection of barely visible impact damage in composite panels has been predicted.
Carbon fiber laminate composites, consisting of layers of polymer matrix reinforced with high strength carbon fibers, are
increasingly employed for aerospace structures. They offer advantages for aerospace applications, e.g., good strength to
weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to
detect damage. Depending on the severity of the impact, fiber and matrix breakage or delaminations can occur, reducing
the load carrying capacity of the structure. Efficient structural health monitoring of composite panels can be achieved
using guided ultrasonic waves propagating along the structure. Impact damage was induced in the composite panels
using standard drop weight procedures. The guided wave scattering at the impact damage was measured using a
noncontact laser interferometer, quantified, and compared to baseline measurements on undamaged composite panels.
Significant scattering of the first anti-symmetrical (A0) guided wave mode was observed, allowing for the detection of
barely visible impact damage. The guided wave scattering was modeled using full three-dimensional Finite Element (FE)
simulations, and the influence of the different damage mechanisms investigated. Good agreement between experiments
and predictions was found. The sensitivity of guided waves for the detection of barely visible impact damage in
composite panels has been verified.
Composite materials such as carbon fiber reinforced panels offer many advantages for aerospace applications, e.g., good strength to weight ratio. However, impact during the operation and servicing of the aircraft can lead to barely visible and difficult to detect damage. Depending on the severity of the impact, fiber breakage or delaminations can be induced which reduce the functionality of the structure. Efficient structural health monitoring of such plate-like components can be achieved using guided ultrasonic waves propagating along the structure and covering critical areas. However, the guided wave propagation in such anisotropic and inhomogeneous materials needs to be understood from theory and verified experimentally to achieve sufficient coverage of the structure. Using non-contact laser interferometer measurements the guided wave propagation in carbon fiber reinforced panels was investigated experimentally. Impact damage was induced in the composite panels and the guided wave scattering at the damage measured and quantified. Good agreement with theoretical wave propagation predictions was found and barely visible impact damage in composite panels detected.
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