Application of the ultrasonic guided wave tomography in structural health monitoring of composites
A Jankauskas and L Mažeika
Composite materials have been used in many different fields (aerospace, civil infrastructure, automobile industries, etc) for their specific properties, such as high strength, high stiffness and light weight. However, composite materials are often damaged by low-velocity impacts because of their low transverse strength. Low-velocity impacts loaded on composites may cause barely visible but considerable internal damage and result in various types of damage, such as delamination, fibre breakage or matrix cracking. Inspection of large areas of a structure employing the traditional non-destructive testing (NDT) approach is time consuming and more difficult when the structures are to be monitored in situ. At the same time, there is a high demand of inspection methods allowing to know the integrity of in-service structures on a continuous real-time basis. Hence, it calls for the development of an effective inspection technique that could detect the damage promptly and thus ensure the safety of these composite materials.
Ultrasonic guided waves have been widely used for the structural health monitoring (SHM) of various ageing engineering components to maintain their safe, reliable and optimal performance. With the advantages including long propagation distance, low cost and good sensitivity to various defects, ultrasonic guided waves have attracted tremendous attention for testing and evaluating composite materials during the past decade. These waves are known to be sensitive to the change in elastic modulus of material and possess minor amplitude damping, which enables large structures to be inspected with good spatial coverage using only a few transducers and to detect both the surface and internal defects. Here, using a sparse array of such guided wave sensors mounted on/in the composites the entire area of the object could be monitored rapidly and continuously in terms of readily interpretable images by exploiting the developments of tomography. Hence, the aim of this work was to develop a guided wave tomography SHM method to quantify the changes in material properties of a composite with a stiffness defect. The technique has been developed on the basis of the S0 mode Lamb wave transmission tomography by using macro-fibre composite (MFC) sensors for excitation and reception of guided waves. The performance of the proposed technique was proven with 2D/3D numerical simulations and experiments on the composite samples with artificial defects.
Ultrasonic guided waves have been widely used for the structural health monitoring (SHM) of various ageing engineering components to maintain their safe, reliable and optimal performance. With the advantages including long propagation distance, low cost and good sensitivity to various defects, ultrasonic guided waves have attracted tremendous attention for testing and evaluating composite materials during the past decade. These waves are known to be sensitive to the change in elastic modulus of material and possess minor amplitude damping, which enables large structures to be inspected with good spatial coverage using only a few transducers and to detect both the surface and internal defects. Here, using a sparse array of such guided wave sensors mounted on/in the composites the entire area of the object could be monitored rapidly and continuously in terms of readily interpretable images by exploiting the developments of tomography. Hence, the aim of this work was to develop a guided wave tomography SHM method to quantify the changes in material properties of a composite with a stiffness defect. The technique has been developed on the basis of the S0 mode Lamb wave transmission tomography by using macro-fibre composite (MFC) sensors for excitation and reception of guided waves. The performance of the proposed technique was proven with 2D/3D numerical simulations and experiments on the composite samples with artificial defects.
