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Item type:Publication, Access status: without files , Room temperature R-curve and stable crack growth behaviour of ZrB2–SiC ceramic composites(2019-05-19); ; ; ; R-curve and controlled stable crack growth behaviour of ZrB 2 –17vol.-%SiC and ZrB 2 –45vol.-%SiC ceramic composites was studied on V-notched samples using four-point bending at room temperature. The rising K 1R behaviour was determined as a function of the crack extension Δa with a crack bridging mechanism being dominant in such behaviour. Significant differences in crack growth rates were found within the same composition of ceramics simply as the crack length varied during crack growth processes. These differences are indicative of the significant influence of microstructural parameters of the ceramics on crack propagation. The peculiarities of stress intensity factor K 1 and the crack growth-specific behaviour in ZrB 2 –SiC particulate ceramic composites are discussed.Publicationtype: Journal Article223 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Stable crack propagation in free standing thermal sprayed Al2O3 and Al2 O3 [sbnd]ZrO 2[sbnd]TiO2 coatingsDue to their unique properties and structure, thermally sprayed ceramics are applied in many fields. Their applications range from engineering ceramics to the use in high temperature units, especially since an improved thermal shock performance was observed. The present study presents an analysis of structural and mechanical properties of thermal sprayed alumina-rich coatings at room temperature. Microstructure and phase composition were analysed by scanning electron microscopy and X-ray diffraction. For pure alumina material, high temperature X-ray diffraction was performed additionally and yielded a phase transition within heating to 1200 °C. Micrographs present typically layered and chaotic microstructure, streaked by microcracks. Cyclic loading test-procedures and the resulting load-displacement-curves revealed a pronounced R-curve-behaviour for coatings of pure Al 2 O 3 and Al 2 O 3 [sbnd]ZrO 2 [sbnd]TiO 2 compositions.Publicationtype: Journal Article204 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Comparative study of static and cyclic fatigue of ZrB2-SiC ceramic compositesRoom temperature static and cyclic fatigue of ZrB2-32 vol% SiC and ZrB2-45 vol% SiC particulate ceramic composites has been studied. It was established that the presence of grain bridging plays an important role in the lifetime and time dependent mechanical performance of ZrB2-SiC composites. It was also established that the cohesive strength of grain boundaries of the composites was a determining factor if grain bridging would occur during crack growth, as the grain boundaries strength would determine the pathway of the moving crack. Grain bridging was limited in ZrB2-32 vol% SiC leading to the absence of a cyclic fatigue effect, while grain bridging indeed occurred in ZrB2-45 vol%SiC contributing to a cyclic fatigue effect which limits the lifetime of the composite. Such differences were responsible for the occurrence of R-curve behavior in ZrB2-SiC ceramic composites.Publicationtype: Journal Article159