The 5th International Conference on Material Strength and Applied Mechanics (MSAM 2022)

Abstract: Fibrous materials are becoming critical technological applications due to their high mechanical performances and low mass. When the fibrous texture is subjected unidirectional strain along one of the axis, the deformations are inherently nonlinear the corresponding stress depend on the underlying material properties. It is widely accepted that the mechanical behavior depends on the strength and the toughness of single fibres as well as on their geometrical arrangement. Little is known on the deformation mechanism and rigidity of spun fabrics despite of the fact that strength and load bearing capacity of these materials are important factors for several technological and biomedical applications. Unidirectional strain-controlled experiments on fibrous electrospun networks during elongation have been studied. The aim of the project to determine and classify the essential mechanical and structural parameters that control the elasticity of biological- and artificial fibrous tissues. Experimental technique combined with the modern statistical theories provide significant potential for the characterization of fiber texture during deformation and suggests reliable mechanical models. The study aims were also to understand and characterize the damage formation in weak electrospun fibers subjected to an external force. We have found a characteristic (typical) load - elongation dependence for the 2D electrospun fiber mats. At the beginning of the applied load, the force has an approximate linear relationship in the low strain regime. At some higher elongation, the slope of this dependence is continuously decreasing and the stress reaches a maximum. Then, increasing the extension, the force declines. Detailed analysis of the shape of the loading curves were carried out by enlarging parts of the loading curves. We have found at small scale that the loading curves show tooth-like profile. These experiments reviled that the unusual loading curve is the result of continuous stiffness reduction caused by damage formation due to either rupture of adhesive fiber-fiber bond fracture or fiber degradation. It is important to know how microscopic failure processes gives rise to macroscopic deformation. Two basically different theoretical approaches have been introduced recently. The Fiber Bund Model (FBM) and the Sacrificial Bond and Hidden Length (SBHL) model. The FBM model takes into account the fiber breaking during deformation, the SBHL model describes the effect of fiber slipping and uncoiling. Both approaches result in similar sequential force drops during elongation, however the FBM model predicts stiffness reduction, while the SBHL model predicts toughening during elongation. Our working hypotheses is based on the assumption, that in real weak fibrous texture, both fiber sliding and unfolding as well as fiber splitting occur during deformation. In this proposal an effort is made to interpret of the unusual mechanical properties of weak fiber texture on the basis of these theoretical models. Numerical simulation based on FBM and SBHL model provide a better understanding of mechanism of deformation. The reported experimental technique has significant potential for the characterization of fiber texture and suggests a further numerical simulations and development of probabilistic models for the load bearing behavior of electrospun fibers.

REFERENCES:
E.Sipos,T.Kaneko, M.Zrinyi: SCIENTIFIC REPORTS 2816 6 (2019)
E.Sipos, M.Zrinyi: JOURNAL OF MOLECULAR LIQUIDS 329 115459 (2021)

Biography: Prof. Zrinyi got his Diploma (chemistry) in L. Eötvös University, Hungary in 1975. He got PhD in 1977 and Doctor of Science in 1987. From 1993 to 2008 he acted as Professor of Physical Chemistry at Budapest University of Technology and Economics. Between 1994 and 2007 he served as Head of the Department of Physical Chemistry. From 2004 to 2008 he was the Vice-Rector of Budapest University of Technology and Economics. In 2008 he moved to Semmelweis University, Department of Biophysics and Radiation Biology. From 2021 he is Professor Emeritus, in Semmelweis University. In 2007 he was elected as Corresponding Member of Hungarian Academy of Sciences, and in 2012 he became ordinary member. The research interests of Prof. Zrinyi are polymer- and colloid science, soft matters and biophysics. He published 4 books (in Hungarian), 11 chapters in various books (in English, Japanese and Chinese) and, more than 350 papers and articles in scientific journals with Hirsch index of 46. Recent scientific activity is devoted to mechanics of fibrous materials.