On 13 October 2025, Laura Balangé presented the outcome of her doctoral research titled " Geometrische Qualitätssicherung für kernlose Faserverbundsysteme (Geometric quality assurance for coreless fibre composite systems)" in front of the doctoral committee.
Congratulations to Laura Balangé on her great achievement.
Doctoral Committee
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Chair: |
apl. Prof. Dr.-Ing. Norbert Haala (IFP) |
Laura Balangé and the doctoral committee
Abstract Doctoral Research
Due to global population growth, the demand for living space is one of the key challenges of our time. To meet the resulting demand, a sustainable and resource-saving construction method, that can be adapted to a wide variety of building types, is required. These challenges are being addressed in the Cluster of Excellence “Integrative Computational Design and Construction for Architecture” (IntCDC) at the University of Stuttgart. One of the design approaches investigated in IntCDC are the fibre reinforced polymers. These consist of different types of fibres, such as carbon or natural fibres, which are impregnated with epoxy resin. The wet fibres are then wound into a net structure within a frame construction. The intersection of individual fibre bundles results in fibre-fibre interaction, which significantly influences the stability of the component. As the interaction also leads to deformation of the individual fibre bundles, the shape and size of the fibre cross-sections are also relevant for the stability of the component. To be able to achieve a high-quality component, it is important to be able to precisely predict the specific geometric characteristics of the components and to determine them after production.
For this reason, a quality assurance concept needs to be developed to produce fibre composite components. A particular focus here lies on the geometry of the individual components. In addition to the position and orientation of the individual fibre bundles, their intersections are also of crucial importance, as they have a direct influence on the physical properties of the component. In addition, the possibilities of determining the cross-sectional areas are considered.
The quality assurance carried out in this work is based on measurements using a terrestrial laser scanner. To achieve the high quality of the measurement results, different laser scanners were first analysed regarding their suitability and interaction with the specimen material. The most efficient and adaptable measurement configuration was then determined to measure a wide variety of specimens. The individual line segments are then segmented from the measured point clouds using a 3D Hough transformation. Furthermore, a straight-line estimation is carried out. Additional boundary conditions are introduced to improve the quality of the results by filtering out incorrect lines. To obtain the coordinates of the fibre intersection points in addition to the individual straight lines of the fibre segments, the intersection points or, since the estimation usually results in skewed straight lines in space, the minimum distance between two straight lines is determined to obtain the intersection point coordinates. These intersection points are connected by the estimated and adjusted straight lines of the line segments and thus form the network structure of the object. Finally, the fibre cross-section areas are determined. For this purpose, the individual fibre segments are divided into sections, and all measuring points of a section are projected onto a plane that has the direction vector of the associated straight line as a normal vector. The convex hull and an alpha-shape are now determined for these projected points. The cross-sectional area can be determined by means of the Gaussian area formula using the defined boundary points. Finally, the quality of the component and the evaluation can be assessed.
The measurement and evaluation concept presented here is applied to test data sets of varying size and complexity. For this purpose, simulated data sets as well as data sets with existing reference measurements are used. The findings are then applied to data sets from production processes without a reference and to geometric quality control during production. Finally, the measurement and evaluation concepts developed are applied to real components. Firstly, it is shown that it is possible to capture the test objects using terrestrial laser scanning. However, the choice of laser scanner is crucial for the quality of the measurement result. The investigations carried out showed that the choice of a laser scanner that uses the time-of-flight method for distance measurement (impulse scanner) and has the smallest footprint is the most suitable for this application. For the reconstruction of the geometry, it was shown that the determination of the geometric parameters from laser scanner point clouds is very well possible and that line segments, intersection points as well as cross-sectional areas can be determined. For the analysed specimens, it was shown that a complete segmentation of all line segments and intersections was always possible if a network could be built for the specimen considered. For the cross-sections, it was shown that the results obtained were highly satisfactory with deviations of less than 1 mm compared to reference measurements from ATOS measurements and alternative microsection measurements. It also shows that the quality of the results depends less on the size of a component and more on its complexity.
Evaluation steps to extract geometric information from point clouds
Papers of which the dissertation consisted
The dissertation is a monograph.
Important papers produced during the research:
Balangé, L., & Schwieger, V. (2025). Possibilities and challenges of measuring small fibre composite system structures using terrestrial laser scanning. FIG Working Week2025, 6-10 April 2025, Brisbane, Australia. https://www.fig.net/resources/proceedings/fig_proceedings/fig2025/papers/ts02i/
TS02I_balange_schwieger_13002.pdf
Balangé, L., Sprügel, N., & Schwieger, V. (2023). Segmentierung und Modellierung von Fasern für die Qualitätssicherung von Faserverbundsystembauteilen mittels terrestrischem Laserscanning. In A. Wieser (Ed.), Beiträge zum 20. Internationalen Ingenieurvermessungskurs Zürich 2023. Wichmann VDE Verlag, Berlin. https://www.vde-verlag.de/buecher/537734/ingenieurvermessung-23.html
Balangé, L., Harmening, C., Duque Estrada, R., Menges, A., Neuner, H., & Schwieger, V. (2022). Monitoring the production process of lightweight fibrous structures using terrestrial laser scanning. 5th Joint International Symposium on Deformation Monitoring, Valencia, Spain. https://doi.org/10.4995/JISDM2022.2022.13830