• Tinga, Tiedo
• Loendersloot, Richard
• Grooteman, Frank
• Marinho, Natália

Abstract

Modern aircraft design acknowledges integrity, superior strength-to-weight ratio, and safety as critical priorities, which has led to the development of monitoring and maintenance techniques for composite structures. However, composite materials pose the risk of introducing damage that cannot be identified visually, namely barely visible impact damage (BVID). If not detected and repaired in time, damage to the structure can compromise its performance and integrity. Therefore, structural health monitoring (SHM) is an emerging technology that can enhance BVID detection in composite structures. Using ultrasonic waves to locate and characterize an impacted region in composite materials is one of the most promising SHM techniques for quantitative impact identification. Although previous studies use guided waves to assess impact in composite materials, few have addressed inservice inspection, and still, few have attempted to quantify impact severity information from the measured signals to full-scale engineering structures. The present investigation addresses these challenges by developing measures of impact identification based on features extracted from ultrasonic waves. Hence, the research aims to develop a monitoring method using combined sensing technologies to gather data from the system and then translate it into predictions about its health. It requires research across multiple disciplines, such as signal processing, data analysis, damage modeling, dynamics, and sensing technologies. This work proposes to combine the building block (B.B.) approach and the design of experiments (DOE) for guided wave-based structural health monitoring (GWSHM). This practical and systematic approach minimizes the number of tests needed for realistic and large structures by building data from lower-level to higher-level systems. Researchers have conducted lowenergy impact tests on a square (1x1m) aluminum and composite plates in the current research phase. Several sensor signal features and the effect of signal response for various energy levels have been examined using the impact response data generated from three different sensor types: Fiber Bragg Grating (FBG), Piezoelectric Patch Transducer (PZT), and Optical Acoustic Emission (OptimAE). Therefore, the present work compares the performance and reliability of FBGs and OptimAE sensors using PZT-based sensors as a reference. In addition, this study describes a systematic experimental approach and analyzes preliminary results over a range of energy levels<br/>below the damage onset. The results showed that the distance from sensors and the directivity effect (for FBG) affect the sensitivity and signal strength. Furthermore, considering the requirements of SHM sensors, the performance also varies with different sensing technologies. In the next stage, SHM analysis will address the effect of structural elements with added complexity (i.e., stiffeners and variable thickness).

Topics

• impedance spectroscopy
• phase
• experiment
• aluminium
• strength
• composite
• impact test
• ultrasonic
• acoustic emission
• impact response