Krenkel, Walter
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Krenkel, Walter
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Krenkel, Walter
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Item type:Publication, Fatigue behavior and residual strength evolution of 2.5D C/C-SiC composites(Elsevier {BV}, 2016-08-20); ; ; ; The residual tensile strength (RTS) evolution of a chemical vapor infiltration and liquid silicon infiltration based 2.5 dimensional reinforced C/C-SiC (2.5D C/C-SiC) composites after fatigue loadings has been investigated. The results show that the fatigue limit (106 cycles) of the 2.5D C/C-SiC composites reaches 58.2 MPa, which corresponds to 75% of the virgin static tensile strength (77.7 MPa). Moreover, an ultimate strength enhancement is observed after fatigue loading. The most pronounced RTS increases to 92.5 MPa when specimens are subjected to fatigue stress of 69.3 MPa for 105 cycles. The microstructural analysis indicates that RTS after cyclic loading is affected by the formation and propagation of cracks and interfacial degradation. Furthermore, a model proposed in this work can well evaluate the RTS of the composites in relation to the number of the applied fatigue cycles.journal articleBand:36Heft:16100 112 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Mechanical behavior of LSI based C/C-SiC composites subjected to flexural loadings(Elsevier {BV}, 2017-02-14); ; ; ; In general, flexural loads result in more complicated and uneven stress distributions in specimens, compared to axial loading. This study reports the influence of flexural fatigue loads including different stress levels and cycles on the mechanical behavior of a 3D C/C-SiC composite. The cyclic tensile loads in the lower part of the specimens result in strength enhancement after short fatigue duration with the expense of decreased flexural modulus due to the fatigue damage such as cracking and interfacial degradation. Whereas the upper part of the post-fatigue specimens, which is almost free of fatigue damage under compressive stress, can still properly deflect the cracks and result in quasi-plastic failures like virgin specimens. Most notably, specimens will suffer strength decline rapidly, after 50,000 cycles with maximum stress of 95 MPa for instance, because of considerable stress concentrations and wear of fibers at 90 fiber bundles in the lower part.journal articleBand:9583 86 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Damage analysis of 2.5D C/C-SiC composites subjected to fatigue loadings(Elsevier {BV}, 2019-03-11); ; ; ; Damage analyses of a ceramic matrix composite during fatigue and quasi-static loads were performed by acoustic emission (A.E.) monitoring. The material studied was a 2.5D C/C-SiC composite produced by chemical vapor infiltration followed by liquid silicon infiltration. The analysis done during the first 200 cycles of a fatigue test showed that the number of A.E. hits is a good parameter for the quantification of damage. Furthermore, the A.E. hit energy was associated with the type of damage. In this sense, the damage developed during the fatigue loading was related to matrix crack initiation, propagation and re-opening, as well as fiber-matrix friction. Quasi-static tests on post-fatigue samples showed that the previous fatigue loadings increased the material`s damage threshold and hindered the development of new damage. Particular attention was given to the sample after 2,000,000 cycles as this sample showed distinct A.E. signals that could be related to fiber debonding.journal articleBand:39Heft:7110 107