Strain hardening cement-based composites (SHCC) and textile reinforced concrete (TRC) are two types of novel cementitious materials which can be used for strengthening structural elements against impact loading. Under tensile loading, these composites exhibit a strain hardening behavior, accompanied with formation of multiple cracks. The multiple cracking and strain hardening behavior yield a high strain and energy absorption capacity, thus making SHCC and TRC suitable materials for impact resistant structures or protective layers.
The design and optimization of such composites for impact resistant applications require a comprehensive characterization of their behavior under various impact
loadings. Specifically, the rate dependent behavior of the composites and their constituents, i.e. matrix, reinforcement, and their bond, need to be described.
In the context of dynamic testing, SHCC, TRC and their constituents require customized experimental setups. The geometry of the sample, ductility of the material, the need for adapters and their influence on the measurements, as well as the influence of inertia are the key aspects which should be considered in developing the impact testing setups.
The thesis at hand deals with the development process of various impact testing setups for both composite scale and constituent scale. The crucial aspects to be taken into account are discussed extensively. As a result, a gravity driven split-Hopkinson tension bar was developed. The setup was used for performing impact tension experiments on SHCC, TRC and yarn-matrix bond. Moreover, its applicability for performing impact shear experiments was examined. Additionally, a mini split-Hopkinson tension bar for high speed micromechanical experiments was designed and built. In the case of compressive loading, the performance of SHCC was investigated in a split-Hopkinson pressure bar.
The obtained results, with focus on tensile experiments, were evaluated concerning their accuracy, and susceptibility to inertia effects. Full-field displacement measurement obtained by digital image correlation (DIC) was used in all impact experiments as a tool for visualizing and explaining the fracture process of the material in conjunction with the standard wave analysis performed in the split-Hopkinson bars.Moreover, the rate dependent behaviors of the composites were clarified with respect to the rate dependent behavior of their constituents.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:72981 |
| Date | 01 December 2020 |
| Creators | Heravi, Ali Assadzadeh |
| Contributors | Mechtcherine, Viktor, Ožbolt, Joško, Mobasher, Barzin, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
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