Creep of chemically vapour deposited SiC fibres

DiCarlo, James A.

doi:10.1007/bf01144723

Cited by 116 publications

(48 citation statements)

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“…This empirical relation has been validated by experiments on several high strength ceramics (Dicarlo, 1986(Dicarlo, , 1994. A, l and p are constants characterizing the inelastic response at times t from the application of the constant stress.…”

Section: Assumptions Utilized For the Development Of The Modelsmentioning

confidence: 86%

On the effect of fiber creep-compliance in the high-temperature deformation of continuous fiber-reinforced ceramic matrix composites

Baxevanis

Plexousakis

2010

International Journal of Solids and Structures

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a b s t r a c tCreep models for unidirectional ceramic matrix composites reinforced by long creeping fibers with weak interfaces are presented. These models extend the work of Du and McMeeking (1995) [Du, Z., McMeeking, R. 1995. Creep models for metal matrix composites with long brittle fibers. J. Mech. Phys. Solids 43, 701-726] to include the effect of fiber primary creep present in the required operational temperatures for ceramic matrix composites (CMCs). The effects of fiber breaks and the consequential stress relaxation around the breaks are incorporated in the models under the assumption of global load sharing and time-independent stochastics for fiber failure. From the set of problems analyzed, it is found that the high-temperature deformation of CMCs is sensitive to the creep-compliance of the fibers. High fiber creep-compliance drives the composite to creep faster, leading however to greater lifetimes and greater overall strains at rupture. This behavior is attributed to the fact that the greater the creep-compliance of the fibers, the higher the creep rate but the slower the matrix stress relaxation -since the matrix must deform with a rate compatible with the more creep-resistant fibers -and therefore the less the load carried by the main load-bearing phase, the fibers. As a result, fewer fibers fail and less damage is accumulated in the system. Moreover, the greater the creep-compliance of the fibers, the slower the matrix shear stress relaxation -and thus the lower the levels of applied stress for which this effect becomes important. The slower the shear stress relaxes, the slower the ''slip" length increases. Due to the Weibull nature of the fibers, the fiber strengths at the smaller gauge length of the slip length are stronger; therefore fewer fibers undergo damage. Hence, high fiber creep-compliance is desirable (in the absence of any explicit creep-damage mechanism) in terms of composite lifetime but not in terms of overall strain. These results are considered of importance for composite design and optimization.

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Section: Assumptions Utilized For the Development Of The Modelsmentioning

confidence: 86%

On the effect of fiber creep-compliance in the high-temperature deformation of continuous fiber-reinforced ceramic matrix composites

Baxevanis

Plexousakis

2010

International Journal of Solids and Structures

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“…For example, recovery tests on the SCS-6 fiber show that the total creep strain typically consists of an anelastic or recoverable component plus a viscous or non-recoverable component [11]. Generally the viscous component continues to increase with time, while the anelastic component saturates with time to a value no greater than ∼2 times the initial elastic component [12].…”

Section: Temperature-dependent Mechanical Propertiesmentioning

confidence: 98%

Non-oxide (Silicon Carbide) Fibers

DiCarlo

Yun

Handbook of Ceramic Composites

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Non-oxide ceramic fibers are being considered for many applications, but are currently being developed and produced primarily as continuous-length structural reinforcement for ceramic matrix composites (CMC). Since only those fiber types with compositions based on silicon carbide (SiC) have demonstrated their general applicability for this application, this chapter focuses on commercially available SiC-based ceramic fiber types of current interest for CMC and on our current state of experimental and mechanistic knowledge concerning their production methods, microstructures, physical properties, and mechanical properties at room and high temperatures. Particular emphasis is placed on those properties required for successful implementation of the SiC fibers in high-temperature CMC components. It is shown that significant advances have been made in recent years concerning SiC fiber production methods, thereby resulting in pure near-stoichiometric small-diameter fibers that provide most of the CMC fiber property requirements, except for low cost.

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“…The commercially available fiber, SiC, that we have used for most investigations on the aluminide composites has a very low coefficient of thermal expansion (CTE), 5.5xlO~6 °c~' (23). In contrast, the aluminides have typically high CTE's ranging from lOxICr 6 "C-1 for Ti 3 Al+Nb (24), 14.5xlCT 6 "(H for NiAl (25), to as high as 20.9xlCT 6 "C-1 for FeAl (25).…”

Section: Intermetallie and Metal Matrix Compositesmentioning

confidence: 99%