Short Fiber Composite Internal Geometry Influence on the Material’s Load Bearing Capacity and Strength
Artūrs Mačanovskis

30.05.2014. 14:00, Rīgas Tehniskās universitātes Transporta un mašīnzinību fakultātē, Ezermalas ielā 6, 302 auditorijā.

Andrejs Krasņikovs

Igors Tipāns, Aleksandrs Korjakins, Heiko Herrmann

The thesis begins with literature review (first chapter), where the necessity for study of mechanics and micromechanics of single fiber’s behavior in fiberconcrete is justified. Also is emphasized importance to investigate the arrangement and orientation of fibers inside the beam, during it’s cracking under bending loads. Cracking means an appearance of the main crack is crossing the beam and it’s opening under the load by slow pull-out of fibers from the crack’s flanks. In the second chapter are presented the results of experimental investigation of one single fiber pull-out of the concrete matrix. The canal’s surface left in the concrete by the pulled out fiber was studied microscopically, as well as the single fibers (were embedded into concrete and were oriented at different angles towards the pull-out force) pull-out experimental results are were given (curves “force – length of pull-out fiber from the concrete matrix). Experiments were performed using fibers of different length, diameter and material (steel fibers, polymeric fibers). Concrete was used as the matrix. The third chapter describes experimental results on deflection of fiberconcrete prisms bending. Prisms were tested for 4-point bending. Under applied external foced increase in the prism’s, crossection appeared – a main crack, the openings of which were followed depending on the value of the applied load. The prisms containing various concentrations of fibers with different geometry which were dispersed in the material’s volume were studied. The results of the bearing capacity of prisms containing chaotically distributed fibers in the volume were compared to the result of the bearing capacity of prisms having layered structure. Besides, the layer geometry and percentage of fibers in them changed. Then is the chapter presents the results of the performed X-ray analysis for fiberconcrete prisms. The “weak” areas were found out (areas in material containing decreased fiber concentration and oriented unfavorably (perpendicularly to the beam’s longitudinal axis)). This chapter gives the results of the performed experiments for bending of fiberconcrete prisms containing polymeric fibers. The results were analyzed and the maps of fiber arrangement on the crack’s surface were received. Experimentally the inclination angles of each fiber towards the crack’s surface were measured and the diagrams were built. Chapter 4 presents the results of numerical modeling for mould filling by a fiberconcrete mix. Special attention is paid to identification of areas with high vertical speed component gradient. It is assumed that the mentioned areas will lead to increased concentration of unfavorably oriented fibers (due to acting shear flow perpendicularly to the beam’s axis) in the beam’s crossections. The Chapter 5 describes the algorithms of 4 numerical models are predicting the fiberconcrete beam’s bearing capacity under the bending load. Predictions correspond to the stage of macrocrack opening and fiber pull-out from its flanks. Data on mechanics of a single fiber pull-out from the crack’s flanks in the concrete are taken out of the previous chapters. Model 1 – assumes that all fibers are located in the volume chaotically. Model 2 – uses experimental data on fibers location on the crack’s flanks and their orientation. Model 3 – arises from the assumption that all fibers are crossing the crack are located strictly perpendicularly to it’s plane. Model 4 – is used for description of the bearing capacity of layered fiberconcrete beams with different concentration of fibers in the samples. Next chapter is containing work’s conclusions. The thesis is finished by the appendixes and used literature lists. The work contains 164 pages, 165 figures, 7 tables, 12 appendix and 85 information sources.

Polymeric synthetic fiber, Straight steel fiber, pull-out, X-ray pictures, 4-point bending,.Flowing.

Mačanovskis, Artūrs. Short Fiber Composite Internal Geometry Influence on the Material’s Load Bearing Capacity and Strength. PhD Thesis. Rīga: [RTU], 2014. 164 p.

Publication language
English (en)
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