Stiffened carbon-fibre-reinforced composite structures are extensively used in the aerospace industry for constructing aircraft wings, fuselage, and several other structural components. These structures are often prone to damage due to ageing, cyclic loading and impact. The wave propagation based structural health monitoring technique is widely used for identifying such damage in these structures. This paper presents the analysis of guided wave propagation in a repaired stiffened composite aircraft-wing panel, in order to understand the wave propagation phenomenon in such complex multi-layered structure. Towards this, a coordinated theoretical, numerical and experimental investigation has been carried out. The dispersion curves for the structure are theoretically obtained by using a fast and efficient semi-analytical model to study the dispersion characteristics of the propagating guided waves at the high-frequency range. An extensive finite element based numerical simulation of guided wave propagation in the sample structure is carried out in ABAQUS. Based on the theoretically obtained dispersion curves, different wave modes in the signals are effectively identified. It is observed that the presence of a localized patch repair region in the structure significantly influences the wave mode amplitudes and propagation velocities. Laboratory experiments are then conducted, in order to verify the numerical simulation results. A good agreement is noticed between the simulation and experimental results, in all the cases studied. A series of parametric study is also numerically carried out, in order to check the influence of repaired region size on the propagating guided wave modes in the structure.
Jointed composite structures (JCSs) are often used in the marine, automotive and civil engineering industries. In JCS, thin carbon-fiber-reinforced composite laminates are bonded with epoxy adhesives. But, disbonds can occur at the bondinterphase due to variable environmental conditions, cyclic loading, aging, fatigue, amongst others, which may lead to a substantial reduction in load-bearing capacity of the structural assembly. Hence, it is essential to identify these hidden disbonds, and the identification becomes more challenging due to frequent change in ambient temperatures. It is found that the ultrasonic guided wave propagation based inspection technique is suitable for inspection of such complex multilayered structures. The aim of this paper is to investigate the disbond effects on the propagating wave modes in the JCS under variable ambient temperatures. Towards this, a series of finite element based numerical simulation of guided Lamb wave propagation in JCS under variable temperature is carried out in ABAQUS using piezoelectric actuator-sensor transducers. Laboratory experiments are then conducted to investigate the disbond effects and a good agreement is found between the simulation and experimental results.
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