Index of content:
Volume 129, Issue 3, March 2011
- ULTRASONICS, QUANTUM ACOUSTICS, AND PHYSICAL EFFECTS OF SOUND 
Influence of stacking sequence on scattering characteristics of the fundamental anti-symmetric Lamb wave at through holes in composite laminates129(2011); http://dx.doi.org/10.1121/1.3533742View Description Hide Description
This paper investigates the scattering characteristics of the fundamental anti-symmetric (A 0) Lamb wave at through holes in compositelaminates. Three-dimensional (3D) finite element(FE) simulations and experimental measurements are used to study the physical phenomenon. Unidirectional, bidirectional, and quasi-isotropic compositelaminates are considered in the study. The influence of different hole diameter to wavelength aspect ratios and different stacking sequences on wave scattering characteristics are investigated. The results show that amplitudes and directivity distribution of the scattered Lamb wave depend on these parameters. In the case of quasi-isotropic compositelaminates, the scattering directivity patterns are dominated by the fiber orientation of the outer layers and are quite different for compositelaminates with the same number of laminae but different stacking sequence. The study provides improved physical insight into the scattering phenomena at through holes in compositelaminates, which is essential to develop, validate, and optimize guided wave damage detection and characterization techniques.
129(2011); http://dx.doi.org/10.1121/1.3533741View Description Hide Description
An analysis of the scatteringcharacteristics of the fundamental anti-symmetric (A 0) Lamb wave at a delamination in a quasi-isotropic compositelaminate is presented. Analytical solutions for this problem do not exist due to the anisotropic nature and multilayer characteristics of compositelaminates. This study uses a three-dimensional finite element(FE) method and experimental measurements to provide physical insight into the scattering phenomena. Good agreement is found between simulations and experimental measurements. The results show that the A 0Lamb wavescattering at a delamination in compositelaminates is much more complicated than the scattering at a defect in isotropic plates. Scatter amplitudes and scatter directivity distributions depend on the delamination size to wavelength ratio and the through-thickness location of the delamination damage. The study also investigates the feasibility of the common experimental practice of simulating delamination damage by bonding masses to the surface of compositelaminates for guided wave damage detection and characterization methodologies verifications. The results suggest that care is required to use bonded masses to simulate delamination damage for verifying and optimizing damage characterization techniques. In summary, the results of the investigation help to further advance the use of the A 0Lamb wave for damage detection and characterization.