Composites are materials that are composed of two or more building blocks. In this way, one can tailor a composite material. For example, for space travel a strong material that is still light-weight and can withstand high and low temperatures.

A point of attention when using composite materials is that their typical layered structure is sensitive to internal defects and damage. While a small impact (e.g., hail or tools) on an aluminum wingtip of, say, an airplane spout usually causes no more than a small visible dent, that same impact on a composite wing can result in internal damage that - although invisible to the naked eye - can compromise the safety of the aircraft. Therefore, a test procedure is needed that can detect this internal damage quickly and accurately, and do so without causing damage to the composite.

"In my research, I introduce several new non-destructive measurement techniques, based on ultrasound waves, to perform quality control of composite materials," Xiaoyu says.

"On the one hand, I have developed an acoustic microscopy with a novel variable multi-mode focus technique for the characterization of functionally graded metals. With this technique, one can access the acoustic parameters of the different layers," Xiaoyu explains.

"On the other hand, I have developed a planar ultrasound computed tomography (pU-CT) method, using internal layer resonances, for the analysis of (damaged) fiber-reinforced plastics. This method allows to reconstruct in a safe and simple way the internal 3D structure of (damaged) layered fiber reinforced plastics"

"Thanks to my research, composite materials can be increasingly used for industrial applications," concludes Xiaoyu.

Read a more detailed summary or the entire PhD

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PhD Title: Ultrasonic Evaluation of Layer Parameters in Functionally Graded Materials and Fiber Reinforced Polymers

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Contact: Xiaoyu Yang,  Mathias Kersemans

Xiaoyu Yang was born on November 19th, 1993 in Wuhan, People's Republic of China. After finishing his high school education, he moved to Hangzhou to study Electromechanical Engineering at Zhejiang University in 2012. He obtained his BSc degree in 2016, and subsequently pursued a Ph.D. degree in Electromechanical Engineering at Zhejiang University.

His PhD project on the ultrasonic assessment of thin layer materials and functionally graded materials started in September 2016, and has been financially supported by the National Natural Science Foundation of China.

In 2019, Xiaoyu has been selected for the Preference CSC program allowing him to pursue a joint-PhD degree between Zhejiang University and Ghent University. In September 2019, he moved to Ghent, Belgium, to start his research on the ultrasonic assessment of fiber reinforced polymers at the Mechanics of Materials and Structures research group of Ghent University. The results leading to this dissertation entitled "Ultrasonic Evaluation of Layer Parameters in Functionally Graded Materials and Fiber Reinforced Polymers" have been obtained in the framework of a joint-PhD program between Zhejiang University and Ghent University.

The work presented in this dissertation has been performed under the guidance of Bing-Feng Ju (Zhejiang University) and Mathias Kersemans (Ghent University). Xiaoyu is currently the author of 14 publications in peer-reviewed international scientific journals (A1), of which 9 publications as the first author.

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Editor: Jeroen Ongenae - Illustrator: Roger Van Hecke