Damage-enhanced creep and rupture in fiber-reinforced composites

Fabeny, B.

doi:10.1016/1359-6454(96)00027-4

Cited by 27 publications

(24 citation statements)

References 17 publications

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“…Hence, it is actually a critical value for the applied stress, below which the composite suffers only partial failure and the stress on the unbroken fibers tends towards a finite value giving rise to an infinite lifetime. Fabeny and Curtin (1996) have constructed a system similar to (16) describing the overall creep behavior of a composite with fibers exhibiting steady-state creep. They proved that there exists again a critical value (greater than (20) for the applied stress, below which the composite has an infinite lifetime with some steadystate creep rate.…”

Section: Assumptions Utilized For the Development Of The Modelsmentioning

confidence: 99%

“…The longitudinal time-dependent deformation of continuous fiber-reinforced composites is the result of diffusional and cavitational creep of the constituents (McLean, 1985;McLean, 1989;Du and McMeeking, 1995;Fabeny and Curtin, 1996), as well as of the strength and evolution of fiber damage and fiber/matrix slippage. The fibers are the stiff, main load-bearing phase with randomly distributed flaws that grow over time and result in sudden fiber breaks where tensile loading is unsupported.…”

Section: Introductionmentioning

confidence: 99%

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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: 99%

Section: Introductionmentioning

confidence: 99%

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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“…The model assumes an elastic cylindrical fiber embedded in an inelastically deforming matrix, similar to the models presented by McLean [15] and Fabeny [16]. The effect of other fibers from the surrounding is assumed to be negligible.…”

Section: Inelastic Concentric Cylinder Modelmentioning

confidence: 99%

Residual stress development during fabrication and processing of gamma-titanium based composites

et al. 2001

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“…At lower rates of loading, the matrix was able to relax in creep and did not fracture, resulting in much-longer composite lifetimes. The McLean approach was expanded by Du and McMeeking 30 and Fabeny and Curtin 31 to incorporate statistical fiber fracture and its influence on creep and rupture but not matrix damage. These works also emphasized that stress transfer across the fiber/matrix interface can also be affected by matrix creep: 30,32,33 the interface shear stress along broken fibers drives creep of the matrix and a subsequent increase in the ineffective length of broken fibers, resulting in time-dependent composite failure.…”

Section: Introductionmentioning

confidence: 99%

Stress Rupture in Ceramic‐Matrix Composites: Theory and Experiment

Halverson

2002

Journal of the American Ceramic Society

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A micromechanically based model for the deformation, strength, and stress-rupture life of a ceramic-matrix composite is developed for materials that do not degrade by oxidative attack. The rupture model for a unidirectional composite incorporates fiber-strength statistics, fiber degradation with time at temperature and load, the state of matrix damage, and the effects of fiber pullout, within a global load sharing model. The constituent material parameters that are required to predict the deformation and lifetime can all be obtained independent of stress-rupture testing through quasi-static tension tests and tests on the individual composite constituents. The model predicts the tertiary creep, the remaining composite strength, and the rupture life, all of which are dependent critically on the underlying fiber-strength degradation. Sensitivity of the rupture life to various micromechanical parameters is studied parametrically. To complement the model, an extensive experimental study of stress rupture in a Nextel 610/alumina-yttria composite at temperatures of 950°and 1050°C is reported. The Larson-Miller and Monkman-Grant life-prediction methods are inadequate to explain the current data. Constituent parameters for this material system are derived from quasi-static tests and literature data, and the micromechanical model predictions are compared with measured behavior. For a slow-crack-growth model of fiberstrength degradation, the lifetime predictions are shorter by two orders of magnitude. When the rupture life is fitted with one parameter, however, the model prediction of the tertiary creep and residual strength at 1050°C agrees well with the experimental results. For a more complex degradation model, the rupture life and tertiary creep at 1050°C can be predicted quite well; however, the spread in residual strength is not, and the lifetimes at 950°C are greatly overpredicted. Thus, the micromechanical model can be successful quantitatively but clearly shows that the rupture life of the composite is extremely sensitive to the detailed mechanisms of fiber degradation. The model has practical applications for extrapolating laboratory lifetime data and predicting life in components with evolving spatial stresses.

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Damage-enhanced creep and rupture in fiber-reinforced composites

Cited by 27 publications

References 17 publications

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

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

Residual stress development during fabrication and processing of gamma-titanium based composites

Stress Rupture in Ceramic‐Matrix Composites: Theory and Experiment

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