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Influence of the Nanoparticle Geometry on the Fracture Toughness and the Fatigue Crack Propagation Behavior of Epoxy Resins

The addition of nanoparticles is an efficient method to improve the fatigue crack propagation behavior of epoxy resins. The aim of the present work is to investigate and to explain the influence of the nanoparticle geometry on fracture toughness and fatigue crack growth behavior. Especially the influence of particle shape, size and aspect ratio is investigated. Therefore spherical, tubular and platy nanoparticles with comparable dimensions and chemical composition were chosen.

The sophisticated aims of the present work require a comprehensive and interdisciplinary study including the selection and surface modification of nanoparticles, the optimization and characterization of the dispersion quality, the analysis of the particles size distribution and finally the characterization of the fatigue crack growth behavior and its interpretation by correlating fracture mechanical approaches with the particle geometry.

According to the results of the present work, the particle geometry influences the fatigue crack growth behavior significantly. The changes in the material properties and the associated toughening mechanisms are explained by correlating the particle geometry with the fracture mechanical theories adapted to fatigue testing.

In general the particle size has significant influence on the apparent toughening mechanisms and thus on the fatigue crack growth behavior. As the particle size exceeds the size of the dynamic crack tip opening displacement, a direct interaction between the nanoparticles and the propagating crack is possible. The very small nano-SiO2 particles contribute to toughening, and to the improvement in FCP-behavior exclusively by local plastic deformation, provoked by particle debonding and subsequent plastic void growth. In this case the improved material behavior is attributed to the large number of nanoparticles and the corresponding delaminations. In case of the size of the nanoparticles exceeding the size of the dynamic crack tip opening displacement in at least one dimension (e.g. synthetic layered silicates) the apparent toughening mechanisms are changing. In this case the more effective crack pinning and crack deflection as well as the higher delocalization of the toughening effects lead to an enhanced FCP-behavior.

Furthermore, a significant influence of the particle shape on the FCP-behavior is observed, whereas the effect of the aspect ratio is small and not always obvious.

Lesen Sie die deutsche Zusammenfassung auf Kunststoffe.de
Author
 Martin Heinz Kothmann

Martin Heinz Kothmann
Lehrstuhl für Polymere Werkstoffe
Universität Bayreuth

Information

Free keywords: Epoxidharz, Ermüdungsrissausbreitung, Nanocomposite, nano-SiO2 , Halloysi-te, Schichtsilikate, Bruchmechanik, Partikelgeometrie, Aspektverhältnis, Zähmodifikation
Institute / chair: Fakultät für Ingenieurwissenschaften der Universität Bayreuth
Language: German
Technical consultant for expert services: Prof. Dr.-Ing. Volker Altstädt (Betreuer), Prof. Dr. Josef Breu
Publication year: 2017
Provider: Wissenschaftlicher Arbeitskreis Kunststofftechnik (WAK) / Kunststoffe.de

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