Abstract
In this study, energy transmission of the guided waves propagating in composite sandwich structures is investigated in a wide range of frequencies using numerical simulations. The effects of different potential defects on the guided wave energy transmission are explored in such structures. Furthermore, the accuracy of homogenization methods for finite element modelling of guided wave propagation in sandwich structures is studied with the aim of reducing the computational burden of the simulations in the low range of frequencies. A 2D finite element model is developed and verified by comparing the results with the dispersion curves. In order to examine homogenization methods, the homogenized stiffness matrices of the sandwich material and the laminate skin are calculated using classical laminate theory. Results show that core-skin debonding causes absence of wave energy leakage from the skin to the core material in that region in a specific range of frequencies. The results are also obtained for the delamination within the skin and compared with the healthy material. Finally, for the guided waves in the low range of frequencies, it is possible to use the homogenization methods to create the finite element models and reduce the solution time.
Highlights
Composite sandwich structures are types of materials which have a lightweight but thick core attached between two thin but stiffer skins, often made of composite laminates. ese types of materials are extensively used in various applications due to their special characteristics such as high bending stiffness, high strength, and excellent dynamic properties together with low weight [1, 2].One of the major challenges in using composite sandwich structures is that they are more likely to be subjected to debonding and failure. is is due to their large weak interfaces between adjacent materials with very different stiffness and strength properties [3]
GW Energy Transfer. e dispersion behaviour of the A0 and S0 wave modes presented in Figure 3 shows a drop in phase velocity of the S0 wave mode at a frequency of approximately 25 kHz. is drop has as a consequence that both wave modes have approximately equal velocities above this frequency
By increasing the propagation time, the high wave magnitudes are transferring to the core material and reache the bottom skin
Summary
Composite sandwich structures are types of materials which have a lightweight but thick core attached between two thin but stiffer skins, often made of composite laminates. ese types of materials are extensively used in various applications due to their special characteristics such as high bending stiffness, high strength, and excellent dynamic properties together with low weight [1, 2]. The majority of the studies show that, in a specific range of frequencies, debonding between the laminate and the core material causes an increase in the signal compared to the baseline. Is is the range of frequencies in which Lamb waves propagating in the top laminate skin shows leaky behaviour meaning that it attenuates quickly because of loss of energy to the core material. It is shown that, at frequencies lower than in the abovementioned studies, debonding between the core material and the skin of the sandwich structure causes creation of reflected waves [11, 12]. Classical laminate theory (CLT) is used to homogenize the sandwich composite structure, and the possibility of using such models for GW propagation in the very low range of frequencies is investigated. In the following debonding between the core material and the laminate skin is referred to as “debonding” and delamination in the laminate skin is referred to as “delamination.”
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