Abstract
This paper presents a new methodology for detecting various types of composite damage, such as delamination and impact damage, through the application of multimode guided waves. The basic idea is that various wave modes have different interactions with various types of composite damage. Using this method, selective excitations of pure-mode guided waves were achieved using adjustable angle beam transducers (ABTs). The tuning angles of various wave modes were calculated using Snell’s law applied to the theoretical dispersion curves of composite plates. Pitch–catch experiments were conducted on a 2-mm quasi-isotropic carbon fiber-reinforced polymer (CFRP) composite plate to validate the excitations of pure fundamental symmetric mode (S0) and shear horizontal mode (SH0). The generated pure S0 mode and SH0 mode were used to detect and separate the simulated delamination and actual impact damage. It was observed that S0 mode was only sensitive to the impact damage, while SH0 mode was sensitive to both simulated delamination and impact damage. The use of pure S0 and SH0 modes allowed for damage separation. In addition, the proposed method was applied to a 3-mm-thick quasi-isotropic CFRP composite plate using multimode guided wave detection to distinguish between delamination and impact damage. The experimental results demonstrated that the proposed method has a good capability to detect and separate various damage types in composite structures.
Highlights
Composite materials have been widely used in aerospace structures due to their advantages of having high specific strength and stiffness, having design flexibility, and being lightweight [1]
Pure S0 and SH0 modes generated by the angle beam transducers (ABTs)–ABT were utilized to detect the simulated delamination and actual impact damage in the 2-mm quasi-isotropic composite plate
To distinguish between damage types, the pure S0 mode and SH0 mode had to be used together. This is because the pure S0 and SH0 modes were both sensitive to actual impact damage, whereas only the pure SH0 mode was sensitive to the delamination simulated by the Teflon insert
Summary
Composite materials have been widely used in aerospace structures due to their advantages of having high specific strength and stiffness, having design flexibility, and being lightweight [1]. Among them, guided wave-based SHM technologies have been used to detect various damage types in composite structures, including delamination [12,13], debonding [14], and impact damage [15,16,17,18]. Toyama and Takatsubo [23] used an ABT and an acoustic emission (AE) transducer to detect impact damage in a crossply composite plate using S0 mode These studies have facilitated our understanding of guided wave-based SHM applications using ABTs. Compared to the widely used S0 mode, the fundamental shear horizontal (SH0) wave is relatively simple, but has been investigated less often, probably due to the traditional notion that SH waves are usually excited by electromagnetic acoustic transducers (EMATs) [24]. A new methodology is presented to detect and separate various composite damage types based on multiple pure-mode guided waves generated by an adjustable ABT pair. The experimental results demonstrate that the proposed method has a good capability to detect and separate various damage types in composite structures
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