Excitation and Reception of Higher-Order Guided Lamb Wave’s A1 and S1 Modes in Plastic and Composite Materials

Abstract

Contemporary technologies are employing composite plate materials developed by using various innovative materials (nanostructures, mica structures, etc.). Application of higher-order modes could allow better detection and characterization of defects characteristic of planar plastic and composite structures, mainly due to shorter wavelength. However, excitation of higher-order modes meets many problems, especially in the case of the air-coupled technique, and is not sufficiently investigated. This is relevant in the cases of paper, high-density polyethylene (HDPE), membranes, GFRP, GLARE, CFRP and other composite structures. The objective of the paper was investigation of the excitation and reception of higher-order guided Lamb wave modes in plastic and composite plates. Therefore, it is appropriate to develop new non-contact ultrasonic measurement methods based on the excitation and reception of guided waves for the study of such objects. The obtained results clearly demonstrate the possibility to excite and receive efficiently different higher-order guided Lamb wave modes with very different phase velocities. The presented comparison of the experimental results with the simulation results showed a good agreement. The combination of air-coupled excitation and non-contact reception enables a non-destructive evaluation and characterization of moving plastic objects and composite structures.

Exciting and Detecting Higher-Order Guided Lamb Wave Modes in High-Density Polyethylene Structures Using Ultrasonic Methods

“…To date, there is little information on the investigated higher-order modes in HDPE samples. There are several works describing and applying ultrasonic waves to thermoplastic pipes [ 7 , 26 , 27 ]. In our case, the aim of this study was to efficiently excite and detect various higher-order guided Lamb wave modes in high-density polyethylene structures using single-element ultrasonic transducers and a phased array.…”

“…First of all, we performed theoretical calculations of the selected sample. The calculations of the Lamb waves were performed using the semi-analytical finite element (SAFE) method [ 27 ]. The calculated dispersion curves of the selected specimen (thickness of 20 mm) are presented in Figure 1 a (the phase velocity) and Figure 1 b (the group velocity).…”

“…They are generally more diffuse compared to zero-order waves. In the frequency ranges above the defined particular cutoff frequencies of the zero-order modes, there are always not a single mode but several higher order modes [ 27 ]. This, however, complicates the analysis of received ultrasound signals.…”

Through thickness inspection in various structures using ultrasonic wave coupling in an embedded fiber optical sensor

“…The theory was also checked by embedding the FBGs into a real composite glass-fibered reinforced polymer (GFRP) structure. Thus, the paper aims in checking the theory of the behaviour of GW S0 (symmetric fundamental mode) [8] through the thickness of the different materials and checking whether the mode shape of the mode changes through the thickness.…”