Over the last years the strengthening of old structures has focused great interest in civil engineering. Often the structures present weak mechanical characteristics due to material deterioration or increase of the load (for example traffic has grown immense in the last years). In order to use materials with great mechanical characteristics but at the same time low influence on the structure, the Carbon Fiber Reinforced Polymers were applied for this intent. The CFRP fibers (strip or textile) are glued on the traction side of the steel concrete elements. The bond between CFRP and concrete has an elastic behavior till the loss of contact. To prevent the failure, the bond could be projected considering a macroscopic formulation but till now, it wasn't thrown light on the tension distribution between the concrete phase in mesoscale. Some studies conducted at the IBMB in Braunschweig put in evidence the difference between the debonding failure for different concrete mixture. Moreover, a correlation between the fracture energy and the roughness of the failure was found. This statements lead to focus the attention on the debonding phenomena for different concrete configuration in order to find the parameter that influences the bond failure.
The goal of the research is to study the debonding phenomena from the small specimen size to the normal scale application. The study aims to find a representative description of the tension distribution at the small scale for the concrete substrate. With the help of computer tomography representations, the geometry of the concrete components could be implemented to create a meso-model for a finite elements application. Moreover, radiographies will be conducted during the debonding test to have an inner representation of the phenomena. The influencing parameter found in the small scale analysis will be proofed also for the long term and cyclic load test in small or big scale.
The final aim of the research is to investigate the debonding mechanism in order to prevent the failure for every kind of configuration and load pattern.
Publications within the framework of the RTG:
Publications in peer-reviewed scientific journals:
P. Carrara, R. Kruse, D.P. Bentz, M. Lunardelli, T. Leusmann, P.A. Varadya and L. De Lorenzis. Improved mesoscale segmentation of concrete from 3D X-ray images using contrast enhancers. Cement and Concrete Composites, 93: 30-42, 2018.
Conference contribution with publication in conference proceedings:
M. Lunardelli, T. Leusmann and H. Budelmann. Improvement of debonding behavior among low strengthconcrete and externally bonded CFRP. CICE 2016 Proceedings (2016).
M. Lunardelli, P. Varady, D. Köhnke, S. Lehmberg and H. Budelmann. X-ray computed tomography: Image processing and applications. In: von Scheven, M.; Keip, M.-A.; Karajan, N. (Edt.): Proceedings of the 7th GACM Colloquium on Computational Mechanics for Young Scientists from Academia and Industry. October 11-13, 2017, Stuttgart, S. 39-43.
T. Leusmann, G. Basutkar, M. Lunardelli and D. Lowke. Characterizing the 3D Mesostructure of High Performance Concrete with the help of Computed Tomography. Proceeding RILEM Spring convention and sustainable materials, systems and structures conference 2019.