Analysis of Thermomechanical Fatigue of Unidirectional Titanium Metal Matrix Composites

Analysis of Thermomechanical Fatigue of Unidirectional Titanium Metal Matrix Composites
Author: YA. Bahei-El-Din
Publisher:
Total Pages: 17
Release: 1993
Genre: Composite materials
ISBN:

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Thermomechanical fatigue (TMF) data have been generated for a Ti-15V-3Cr-3Al-3Sn (Ti-15-3) material reinforced with SCS-6 silicon carbide fibers for both in-phase and out-of-phase testing. Significant differences in failure mechanisms and fatigue life are noted for the in-phase and out-of-phase testing. The purpose of the research reported in this paper is to apply a micromechanics model to analysis of the data. The analysis predicts the stresses in the fiber and in the matrix material during the thermal and mechanical cycling by calculating both the thermal and mechanical stresses and their time-dependent behavior. The rate-dependent behavior of the matrix was characterized and was used to calculate the constituent stresses in the composite. The predicted 0° fiber stress range was used to explain the composite failure. It was found that for a given condition, temperature, loading frequency, and time at temperature, the 0° fiber stress range may control the fatigue life of the unidirectional composite.

Titanium Matrix Composites

Titanium Matrix Composites
Author: Shankar Mall
Publisher: CRC Press
Total Pages: 478
Release: 2020-01-29
Genre: Technology & Engineering
ISBN: 1000717658

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A review and summary of advancements related to mechanical behavior and related mechanics issues of titanium matrix composites (TMCs), a class of high-temperature materials useful in the propulsion and airframe components in advanced aerospace systems. After an introduction to TMCs, different authors review and summarise the advancements related to mechanical behavior and related mechanics issues of TMCs.

Methodologies for Predicting the Thermomechanical Fatigue Life of Unidirectional Metal Matrix Composites

Methodologies for Predicting the Thermomechanical Fatigue Life of Unidirectional Metal Matrix Composites
Author: RW. Neu
Publisher:
Total Pages: 23
Release: 1996
Genre: Elevated temperature
ISBN:

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Parameters and models to correlate the cycles to failure of a unidirectional metal matrix composite (SCS-6/Timetal 21S) undergoing thermal and mechanical loading are examined. Three different cycle types are considered: out-of-phase thermomechanical fatigue (TMF), in-phase TMF, and isothermal fatigue. A single parameter based on either the fiber or matrix behavior is shown not to correlate the cycles to failure of all the data. Two prediction methods are presented that assume that life may be dependent on at least two fatigue damage mechanisms and therefore consist of two terms. The first method, the linear life fraction model, shows that by using the response of the constituents, the life of these different cycle types are better correlated using two simple empirical relationships: one describing the fatigue damage in the matrix and the other fiber-dominated damage. The second method, the dominant damage model, is more complex but additionally brings in the effect of the environment. This latter method improves the predictions of the effects of the maximum temperature, temperature range, and frequency, especially under out-of-phase TMF and isothermal fatigue. The steady-state response of the constituents is determined using a 1-D micromechanics model with viscoplasticity. The residual stresses due to the CTE mismatch between the fiber and matrix during processing are included in the analysis.

Damage Evolution in Metal Matrix Composites Subjected to Thermomechanical Fatigue

Damage Evolution in Metal Matrix Composites Subjected to Thermomechanical Fatigue
Author:
Publisher:
Total Pages: 4
Release: 1995
Genre:
ISBN:

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A thermomechanical analysis of unidirectional continuous fiber metal matrix composites is presented. The analysis includes the effects of processing induced residual thermal stresses, interface cracking, and inelastic matrix behavior on damage evolution. Due to the complexity of the nonlinear effects, the analysis is performed computationally using the finite element method. The interface fracture is modeled by a nonlinear constitutive model. The problem formulation is summarized and results are presented for a four-ply unidirectional SCS-6/[beta]21S titanium composite under high temperature isothermal mechanical fatigue.

Micromechanics Analysis and Life Prediction of Titanium Matrix Composites

Micromechanics Analysis and Life Prediction of Titanium Matrix Composites
Author: T. Nicholas
Publisher:
Total Pages: 10
Release: 2006
Genre: Composite materials
ISBN:

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The response of a unidirectional SCS-6/Ti-6Al-4V composite is evaluated under a range of isothermal fatigue (IF) and thermomechanical fatigue (TMF) conditions. Both processing and thermomechanical test conditions are simulated using a cylinder in cylinder code, FIDEP, which treats the fiber as thermoelastic while the matrix is characterized using a recent version of the Bodner-Partom constitutive law. Computed stresses and strains in the constituents are obtained after 10 cycles of loading and are used as input into a new and simpler version of a life fraction model. Applied stress at temperature and computed matrix strains are used for the time-dependent and matrix fatigue terms in the model, respectively. Cyclic stress-strain behavior of the matrix material is also computed and used, together with fatigue life data, to identify the governing mechanisms and to explain the observed trends in fatigue life as a function of frequency and applied stress level. Comparisons of fatigue behavior with that of SCS-6/Timetal 21S illustrate differences when tested under nominally similar conditions.

An Experimental and Analytical Investigation of Titanium Matrix Composite Thermomechanical Fatigue

An Experimental and Analytical Investigation of Titanium Matrix Composite Thermomechanical Fatigue
Author: D. Ball
Publisher:
Total Pages: 32
Release: 1996
Genre: Alloys
ISBN:

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The results of complementary experimental and analytical investigations of thermomechanical fatigue of both unidirectional and crossply titanium matrix composite laminates are presented. Experimental results are given for both isothermal and thermomechanical fatigue tests which were based on simple, constant amplitude mechanical and thermal loading profiles. The discussion of analytical methods includes the development of titanium matrix composite laminate constitutive relationships, the development of damage models and the integration of both into a thermomechanical fatigue analysis algorithm. The technical approach begins with a micro-mechanical formulation of lamina response. Material behavior at the ply level is based on a mechanics of materials approach using thermo-elastic fibers and an elasto-thermo-viscoplastic matrix. The effects of several types of distributed damage are included in the material constitutive relationships at the ply level in the manner of continuum damage mechanics. The modified ply constitutive relationships are then used in an otherwise unmodified classical lamination theory treatment of laminate response. Finally, simple models for damage progression are utilized in an analytical framework which recalculates response and increments damage sizes at every load point in an applied thermal/mechanical load history. The model is used for the prediction of isothermal fatigue and thermomechanical fatigue life of unnotched, crossply [0‡/90‡]s titanium matrix composite laminates. The results of corresponding isothermal and thermomechanical fatigue tests are presented in detail and the correlation between experimental and analytical results is established in certain cases.