Abstract
The study of propagating, evanescent and complex wavenumbers of guided waves (GWs) in high-performance composites using a stable and robust semi-analytical finite element (SAFE) method is presented. To facilitate understanding of the wavenumber trajectories, an incremental material change study is performed moving gradually from isotropic aluminum alloy to carbon fiber reinforced polymer (CFRP) composites. The SAFE results for an isotropic aluminum alloy plate are compared with the exact analytical solutions, which shows that N = 20 SAFE elements across the thickness provides <0.5% error in the highest evanescent wavenumber for the given frequency-wavenumber range. The material change study reveals that reducing the transverse and shear moduli moves the wavenumber solution towards one similar to composite material. The comparison of the propagating, evanescent and complex wavenumber trajectories between composites and aluminum alloy show that antisymmetric imaginary Lamb wave modes always exist in composites although they may not exist in isotropic aluminum alloy at some frequencies. The wavenumber trajectories for a unidirectional CFRP plate show that the range of real wavenumber is much smaller than in the isotropic aluminum alloy. For laminated CFRP composite plates (e.g., unidirectional, off-axis, transverse, cross-ply and quasi-isotropic laminates), the quasi Lamb wave and shear horizontal (SH) wave trajectories are also identified and discussed. The imaginary SH wave trajectories in laminated composites are distorted due to the presence of ±45 plies. The convergence study of the SAFE method in various CFRP laminates indicates that sufficient accuracy can always be achieved by increasing the number of SAFE elements. Future work will address the stress-continuity between composite layers.
Highlights
The guided wave damage detection technique is popular in the nondestructive evaluation (NDE)and structural health monitoring (SHM) community for observing the evolution of the material state in a safety-critical structure
A typical case is that of Guided waves (GWs) traveling in a plate which is bounded by its top and bottom faces; GWs propagate along the plate and parallel to top and bottom plate boundaries
The availability of the complete wavenumber solution for GWs in composite materials opens the road for developing an analytical framework for studying the interaction of guides waves with damage/discontinuities in composite structures using a normal-mode expansion (NME) approach
Summary
The guided wave damage detection technique is popular in the nondestructive evaluation (NDE). Many researchers have reported the experimentally-observed of guided waves upon in composite materials has only been possible, so far, through the finite element method (FEM), interacting with different types of damage [16,17,18,19,20]. The three different groups of GWs corresponding real, imaginary, andisotropic complex metallic wavenumbers composite materials is not as well documented in thetoliterature as it is for plates have very different physical behavior despite being solutions of the same governing equation. The availability of the complete (real, imaginary and complex) wavenumber solution for GWs in composite materials opens the road for developing an analytical framework for studying the interaction of guides waves with damage/discontinuities in composite structures using a normal-mode expansion (NME) approach. The wavenumber trajectories for different CFRP laminates are discussed
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