Advancing Applied Sciences with 4D X-ray Computed Tomography at KU Leuven

Insights into Fiber-Reinforced Polymers: Dynamic Resin Polymerization and In-Situ Tensile Testing Using TESCAN UniTOM Devices

On this insights page, we take a closer look at the 4D X-ray computed tomography (4D XCT) research performed at the KU Leuven XCT Core Facility at KU Leuven in Belgium. Using TESCAN’s UniTOM XL and UniTOM HR XCT devices, researchers are advancing studies in engineering, geosciences and life sciences.The facility recently published two articles on fiber-reinforced polymers, examining these materials during resin polymerization and in-situ tensile testing within the XCT scanner. In both scenarios, time-resolved XCT (either true dynamic or time-lapse) provided unique insights in the behavior of these materials. The results are being used to improve quality, reduce costs, and increase the durability of fiber-reinforced polymers, which are used in automotive, aerospace and renewable energy applications for their unique combination of high strength and low weight.

In a notable experiment published in Acta Materialia, 4D XCT was used in a true dynamic manner with a temporal resolution of 2 minutes and a spatial resolution of 20 µm. Using a custom-developed miniature infusion setup, resin was infused under vacuum into a glass fiber preform, allowing researchers to monitor the polymerization process inside the TESCAN UniTOM XL while continuously rotating the sample. This setup enabled the study of void formation and evolution in the polymer matrix. The results showed that voids grow inside the fiber-reinforced polymer over time due to chemical shrinking of the matrix, showcasing the feasibility of an in-situ infusion and polymerization setup for laboratory-based XCT.  

Figure 1: Custom miniaturized in-situ resin injection and curing stage at KU Leuven XCT Core Facility – from the in-house designed in-situ resin injection and curing stage –( XCT KU Leuven).

The image below provides a graphical overview of the workflow. For more information on the research, please refer to the full paper titled 4D-XCT monitoring of void formation in thick methacrylic composites produced by infusion – available on ScienceDirect.

Figure 2: Graphical abstract showing the workflow for in-situ void characterization during resin infusion and polymerization. From 4D-XCT monitoring of void formation in thick methacrylic composites produced by infusion – (ScienceDirect).

The second research study focused on damage development in carbon fiber-reinforced thermoplastics, more specifically sheet moulding compounds, during tensile testing. In this publication, specially prepared tensile samples with a “dog bone” shape, were mounted inside a Deben CT5000 (Deben UK Ltd.) compression stage, which was installed on the rotation stage of the TESCAN UniTOM XL. In this case, a time-lapse approach was followed, to increase both spatial resolution (4 µm) and signal to noise ratio. The tensile experiment was paused at specific intervals; to allow for scanning and morphological analysis of the sample, as depicted in the image below. 

Figure 3: Image showing the Deben CT5000 stage mounted on the rotation platform of the UniTOM XL (a), the different loading steps for image acquisition (b), and the sample inside the Deben stage (c). From Spatial strain distribution and in-situ damage analysis of sheet molding compounds based on digital volume correlation – (ScienceDirect). 

The results demonstrate that high-quality XCT data, with excellent resolution and contrast between fibers, matrix and voids, allows for detailed tracking of damage development. Furthermore, digital volume correlation (DVC) – a technique where the volumetric differences between time-lapsed images of the same sample under different conditions are analyzed – can be used to map out stress and strain inside the samples, providing a comprehensive visualization. Strain localizations, local void content and local strand orientation were correlated to clarify microcrack formation and evolution in this kind of samples.

Figure 4: Visualization of Z-axial strain in the samples, derived from analyzing the displacement fields in steps 1 (a), 2 (b) and 3 (c).

The full paper can be found at Spatial strain distribution and in-situ damage analysis of sheet moulding compounds based on digital volume correlation – (ScienceDirect). – DOI:  https://doi.org/10.1016/j.compositesb.2025.112220

For more information about the research going on at the KU XCT Leuven Core Facility, visit XCT KU Leuven – Core Facility. 

About KU Leuven

Founded in 1425, KU Leuven is one of Europe’s leading research universities, consistently ranked among the top institutions worldwide. Located in Belgium, it is renowned for its cutting-edge research across various disciplines, fostering innovation and scientific advancements that have a global impact.

Within KU Leuven, the XCT Core Facility specializes in X-ray computed tomography (XCT), offering state-of-the-art imaging solutions for non-destructive material analysis. Equipped with TESCAN’s UniTOM XL and UniTOM HR XCT systems, the facility enables high-resolution 3D and 4D imaging for research in engineering, geosciences, and life sciences. The XCT Core Facility collaborates with academic and industrial partners to advance materials characterization, optimizing materials for applications in aerospace, automotive, and renewable energy sectors.