Original Article Journal of Intelligent Material Systems and Structures 1–19 Ó The Author(s) 2020 Article reuse guidelines: sagepub.com/journals-permissions DOI: 10.1177/1045389X20978294 journals.sagepub.com/home/jim Numerical and experimental investigation of delaminations in a unidirectional composite plate using NDT and SHM techniques Asaad Migot 1 , Hanfei Mei 2 and Victor Giurgiutiu 2 Abstract In this paper, the non-destructive testing (NDT), structural health monitoring (SHM), and scanning laser Doppler vib- rometer (SLDV) techniques were presented to quantify three simulated delaminations inserted at different depths of a unidirectional composite plate. First, the RollerFORM and Omniscan equipment were sufficiently used to identify the delaminations. Second, in conjunction with guided waves, the developed imaging method was successfully used to detect and quantify the interested delaminations. The tuning curves were determined experimentally to define the dominant Lamb wave modes of incident waves. Third, multi-physics three-dimensional finite element simulations of propagating and interacting Lamb waves with delaminations were implemented to extract the wavefield data for wavenumber analy- sis. The experimental part was conducted to validate the numerical results using SLDV. The effect of the delamination depth on the trapped waves generated over the delamination region was studied numerically and experimentally. The results showed that trapped waves could be affected by the delamination depth. Both numerical and experimental results demonstrated that the near surface delamination has strong trapped waves over the delamination region while the far surface delamination has weak trapped waves. The energy distribution maps of numerical and experimental wavefields data sufficiently quantified the interested delaminations. A good agreement was achieved between the numerical and experimental results. Keywords Structural health monitoring, non-destructive testing, composite materials, wave propagation, imaging methods, scat- tered waves, finite element simulation, wavenumber analysis 1. Introduction 1.1. State of the art The advantages of the mechanical properties of compo- site materials have contributed to the development of aerospace structures. These materials have excellent mechanical properties and lightweight compared with metallic materials (Giurgiutiu, 2014; Migot et al., 2020). Different kinds of damage can occur in compo- site structures, such as delamination, matrix crack, and disbonding (Mei and Giurgiutiu, 2019a). These defects may be induced during manufacturing or by external impact and aging. They may grow and subsequently cause structural failure. Delamination represents the most invisible dangerous structural damage, leading to a catastrophic accident (Zou et al., 2000). The develop- ment and design of efficient structural health monitor- ing (SHM) techniques for successfully detecting and quantifying delamination is an argent demand. The anisotropic behavior of composite materials makes the process of detecting damage more difficult compared with metallic materials (Gomes et al., 2018; Mei and Giurgiutiu, 2018). In recent years, various types of non-destructive testing (NDT) techniques have been developed and used to identify the structural damage such as ultrasonic testing, radiographic testing, electro- magnetic testing, etc. (He and Hutchinson, 1989; He et al., 2017). However, NDT methods are much expen- sive and need more experience. The increasing use of aerospace and naval vehicles worldwide has made 1 Quality Assurance Department, Thi-Qar University, Nasiriyah, Iraq 2 Department of Mechanical Engineering, University of South Carolina, Columbia, SC, USA Corresponding author: Asaad Migot, Quality Assurance Department, Thi-Qar University, Almstfawih Street, Nasiriyah 64001, Iraq. Email: migotasaad@gmail.com