Damage Detection in a Composite T-Joint using Guided Lamb Waves

Abstract

Low velocity impact induces barely visible damage in the form of matrix cracking or delamination that can grow under hydro-thermo-mechanical loading and possibly lead to catastrophic failure if not detected at an early stage. A network of piezoelectric transducers can be used to monitor a structure over time for life prognosis through generation and sensing of guided ultrasonic waves. The aim of this study is to design and develop such a sensing method for damage assessment in a composite T-joint subjected to mechanical impacts. In this context, monitoring of Lamb waves in a carbon fibre reinforced polymer (CFRP) T-joint has been completed where dispersion and tuning curves have been obtained. Guided waves are transmitted into the structure through different specified pairs of surface-bonded lead-zirconate-titanate (PZT) transducers in a pitch-catch active structural health monitoring (SHM) approach. With these experiments, Lamb wave fundamental modes (A 0 and S 0) are identified for monitoring impact damage by signal comparison with a prior obtained baseline. Detecting 4J and 10J inner impacts within the central region of the specimen is challenging when using conventional non-destructive techniques (NDT) because of the complex geometry and interference with the web. Signals are compared for the same selected sensing path; and amplitude differences have been observed in tuning curves after the 10J impact, which implies the occurrence of a structural change related to the impact.

Enhancement of Guided Wave Detection and Measurement in Buried Layers of Multilayered Structures Using a New Design of V(z) Acoustic Transducers

“…Since the method is based on the use of focused transducers that possess a large angular aperture, it has the advantage of avoiding the delicate mechanical angular scanning that is necessary with traditional goniometric set-ups [24,25]. Concerning layered structures, Lamb waves are also widely used to control the health of interfacial bonds or the elastic parameters of the different layers [26,27]. In this case, the V(z) method also has the advantage of allowing the guided modes velocities to be measured at a specific location in the sample.…”

Cure monitoring and structural health monitoring of composites using micro-braided distributed optical fibre

“…Structural health monitoring (SHM) involves the permanent integration of sensors into the host structure for continuous and periodic inspection [17][18][19][20][21]. SHM methods facilitate several levels of damage assessment [22], including the detection and location of damage, classification of damage type, quantification of severity, and prognosis on the remaining life of the structure [1,2,[23][24][25]. Since SHM can provide in situ on-demand assessment, without significant downtime of components, the relative cost can be much lower than conventional NDT.…”