Invited Speaker

Abstract: During the fabrication of aerospace composite structures with complex geometries, hybrid manufacturing defects such as fiber wrinkles, resin-rich areas, and voids inevitably occur at regions of abrupt feature transitions. These defects lead to significant variations in the internal microstructure of composite materials, posing potential risks of structural failure. Therefore, the development of reliable nondestructive testing (NDT) techniques is crucial for accurately assessing hybrid manufacturing defects in composites. To address the challenges of defect characterization and the lack of detection benchmarks, an ultrasonic wave propagation analysis model is established for composite structures containing fiber wrinkles and void defects. The study quantitatively correlates porosity/delamination with the frequency dependence of ultrasonic reflections and links fiber wrinkles with the non-reciprocal ultrasonic transmission time-of-flight. This enables reliable decoupling of hybrid defect detection features. Additionally, a multi-frequency ultrasonic imaging method for hybrid defect identification without the need for benchmark comparisons and a wrinkle imaging technique for composite structures without requiring wave velocity input are proposed.

Biography: Zhang Zhen is a researcher at Tongji University. He studied under Professor Su Zhongqing (Editor-in-Chief of Ultrasonics). In April 2021, he joined the research team of Professor Li Yan at Tongji University. He has developed expertise in ultrasonic testing of thick composite structures with variable fiber angles. He has led multiple research projects, including the National Natural Science Foundation of China (NSFC) Youth Program, Aviation Fund, COMAC Innovation Fund, Shanghai Municipal Science and Technology Commission projects, and China Association for Science and Technology (CAST) initiatives. As first author or corresponding author, he has published 17 SCI-indexed papers in journals such as Composite science and technology (CST), Mechanical Systems and Signal Processing (MSSP), and Journal of Sound and Vibration (JSV). His honors include selection for the CAST Youth Talent Support Program, the ACCM12 Young Researcher Award, and the Shanghai Pujiang Talent Program.