Longitudinal guided waves confined in radius filler regions of composite joints

Abstract

This paper studies the feasibility of using ultrasonic guided waves for fast inspection of conformal deltoid radius filler or "Noodle" regions of joints in stringer composite structures. Semi-analytical finite element simulations, supported by experiments and three-dimensional finite element models, are used to demonstrate the existence of a longitudinal guided ultrasonic mode confined or trapped in the Noodle regions. Studies reveal that this mode has attractive properties for rapid screening of Noodle joints, including strong energy concentration, low dispersion, and attenuation. Discussing the physics of mode confinement in light of material differences and geometry, the phenomenon is shown to be related to feature-guiding effects noted in literature recently.

Deep subwavelength ultrasonic imaging using optimized holey structured metamaterials

“…The crack length observed in the μCT- scan is about 1.02 mm, whereas the mean Full width Half Maximum (FWHM, see ref. 23 ) taken from the ultrasonic image (C-scan amplitude data) is about 1.061 mm, which agrees well with the μCT value. This clearly demonstrates the resolving capacity of the metamaterial ultrasonic superlens developed here.…”

Outlier analysis for defect detection using sparse sampling in guided wave structural health monitoring

“…Defect identification and localization has also been recently demonstrated by wave visualization using non‐contact reception at multiple locations for a fixed excitation 12,13 . In general, Lamb waves are widely discussed for delamination detection, and the authors have also published extensively on Lamb wave‐based detection of delamination in simple and complex composite structures 4,7,13,13‐17 . This paper is set in the context of reduction of sensor density for Lamb wave‐based SHM approaches.…”

In-situprocess- and online structural health-monitoring of composites using embedded acoustic waveguide sensors

“…Confinement similar to the effect of a sleeve was achieved by imposing Dirichlet (rigid boundary) conditions at the top and bottom edges of the strip, with continuity conditions at the 'sleeve opening' connecting the 'strip' to the epoxy substrate. The average element size in epoxy region was λ/14, whereas in waveguide it was λ/200 (where λ=wavelength of the wave in the waveguide) [10,11,26]. In-plane excitation consisting of a Hanning-windowed toneburst centered at 100 kHz was provided at one end of the strip, generating S 0 -type guided waves.…”

“…Typically, guided wave based structural health monitoring approaches for composites use surface bonded piezoelectric or magnetostrictive transducers [7][8][9][10][11][12][13][14][15][16]. Surface-bonded transducers generate cylindrical (twodimensional) waves, which decay away from the source, limiting the field of view, especially in inaccessible/ hidden regions of complex structures.…”

“…Here we seek to develop a novel embedded waveguide sensor concept for detecting and monitoring the condition of composites, during curing and service. Guided wave based NDE and SHM approaches have been proposed for composites, but these are typically based on surface-bonded transducers (see [7][8][9][10][11][12][13][14][15][16] referred above). Embedded fiber-based optical waveguide approaches have also been reported [17,18].…”