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Fracture Parameters of AAAS composites with ceramic precursor
Šimonová, H. ; Rozsypalová, I. ; Kumpová, Ivana ; Trčka, T. ; Frantík, P. ; Rovnaníková, P. ; Keršner, Z.
The paper deals with alkali-activated aluminosilicate composites based on ceramic precursors with respect to their characterization by fracture-mechanical parameters. Three composites made of brick dust as a precursor and alkaline activator with silicate modulus Ms = 1.0, 1.2 and 1.4 were investigated. After 28 days of maturation, specimens with nominal dimensions of 40 × 40 × 160 mm were provided by an initial notch to 1/3 of the body height in the middle of the span. At least 6 samples were tested from each composite. Specimens were subjected to three-point bending tests during which force vs. deflection at midspan (F–d) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. By processing these diagrams, the values of the static modulus of elasticity, the effective fracture toughness (including its initiating component) and the specific fracture energy were determined using the effective crack model, Work-of-Fracture method, and Double-K fracture model. After the fracture experiments had been performed, compressive strength values were determined for informational purposes from one part of each specimen that remained after testing. All evaluations included the determination of arithmetic means and standard deviations. To obtain information about the internal structure of composites before and after mechanical testing, the selected body was examined by micro-tomography. Tomographic measurements and image processing were performed for qualitative and quantitative evaluation of internal structure changes with an emphasis on the calculation of porosimetric parameters as well as visualization of the fracture process zone. The fractal dimension of fracture objects was determined.
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