Abstract
An effective approach for an embedded piezo diagnostic layer into thick composite material is presented. The effectiveness of the approach is assessed in comparison to the surface-mounted layer. The proposed manufacturing alleviates difficulties associated with trimming edges of composites when embedding wires. The Electro-Mechanical Impedance technique is used to access the integrity of the piezoelectric sensors bonding process. Comparisons of ultrasonic guided waves are made between embedded and surface-mounted diagnostic layers and their penetration through and across the thickness of the composites. Temperature influences with the range from −40 °C up to 80 °C on embedded and surface-mounted guided waves are investigated. An investigation is carried out into the relationship between amplitude and time-of-flight with temperature at different excitation frequencies. The temperature has significant but different effects on amplitude and phase-shift of guided waves for the embedded layer compared to the surface-mounted layer. A Laser Doppler Vibrometer is used to identify the blue tack and impact damage. Both embedded and surface-mounted layers are shown to be an effective means of generating detectable wave scatter from damage.
Highlights
Thick composites as primarily load-carrying structural components have taken an increasingly significant role in aeronautic applications in recent decades [1,2]
This paper presents for the first time an investigation into embedding the diagnostic layer into thick composites
In order to evaluate the thickness influence on ultrasonic guided waves (UGW) and the distance effect between the damage and sensors on the thick composite laminate, a weighted blue tack was placed on the opposite side of surface-mounted PZT transducers and positioned closer to a PZT transducer
Summary
Thick composites as primarily load-carrying structural components have taken an increasingly significant role in aeronautic applications in recent decades [1,2]. Multi-Actuator Receiver Transduction) LayerTM as an extra ply during lay-up This layer, based on the circuit printing technique, acted as an extra ply during lay-up instead of embedding PZT transducers into composite laminates. A different method was introduced by cutting the part of composite layers at the edge area to make the FBG sensor exit much easier [21]. The layer was shown to pass tests related to extreme environmental and operational conditions As it will be demonstrated in this paper, surface-mounted PZT transducers cannot effectively detect damage in thick composite since they are designed to generate surface waves (Lamb waves).
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