Titanium Metal Matrix Composites Research Articles

Bend stiffness and strength of laminates composed of titanium alloy and titanium metal matrix composite

Bend stiffness and strength of laminates composed of titanium alloy and titanium metal matrix composite

Bend stiffness and strength of laminates composed of titanium alloy and titanium metal matrix composite

Two laminate systems composed of monolithic titanium alloy IMI 834 and Ti alloy/Ti-SiCf have been manufactured by diffusion bonding. Mechanical tests to determine bend stiff ness and strength have been performed and compared with bulk IMI 834 and 100% titanium based metal matrix composite (MMC) control specimens. The effective Young's moduli for the laminates were found to be 1.2-1.8 times greater thanfor 100% IMI 834. The measured moduli were found to agree well withsimple predictions. The bend strengths of the laminates were found to be ∼20% greater than for the constituent materials. Surface strain measurements indicated the presence of residual stresses arising from fabrication.

A micromechanistic-based approach to fatigue life modeling of titanium-matrix composites

Fatigue life modeling of titanium-based metal-matrix composites (MMCs) was accomplished by combining a unified viscoplastic theory, a non-linear micromechanics analysis and a damage accumulation model. The micromechanics analysis employed the Bodner-Partom unified viscoplastic theory with directional hardening. This analysis was then combined with a life-fraction fatigue model to account for the time-dependent component of fatigue damage. The life-fraction fatigue model involved the linear summation of damage from the fiber and matrix constituents of the composite. A single set of empirical constants for the life-fraction fatigue model were established for each of two titanium MMCs reinforced with silicon carbide fibers: SCS-6/Ti-15-3 and SCS-6/ TIMETAL®21s. The predicted fatigue lives were within one order of magnitude of the experimental data for different loading conditions: isothermal fatigue, and both in-phase and out-of-phase thermomechanical fatigue. MMCs modeled included cross-ply, quasi-isotropic and unidirectional SCS-6/TIMETAL®21s, and cross-ply and quasi-isotropic SCS-6/Ti-15-3 laminates.

Materials characterization of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites: Part I. Tensile and fatigue behavior

Flexural fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-ply, continuous silicon carbide (SiC) fibers. The titanium composites had an eightply (0, 90, +45, -45 deg) symmetric layup. Fatigue life was found to be sensitive to fiber layup sequence. Increasing the test temperature from 24 °C to 427 °C decreased fatigue life. Interface debonding and matrix and fiber fracture were characteristic of tensile behavior regardless of test temperature. In the tensile fracture process, interface debonding between SiC and the graphite coating and between the graphite coating and the carbon core could occur. A greater amount of coating degradation at 427 °C than at 24 °C reduced the Ti/SiC interface bonding integrity, which resulted in lower tensile properties at 427 °C. During tensile testing, a crack could initiate from the debonded Ti/SiC interface and extend to the debonded interface of the neighboring fiber. The crack tended to propagate through the matrix and the interface. Dimpled fracture was the prime mode of matrix fracture. During fatigue testing, four stages of flexural deflection behavior were observed. The deflection at stage I increased slightly with fatigue cycling, while that at stage II increased significantly with cycling. Interestingly, the deflection at stage III increased negligibly with fatigue cycling. Stage IV was associated with final failure, and the deflection increased abruptly. Interface debonding, matrix cracking, and fiber bridging were identified as the prime modes of fatigue mechanisms. To a lesser extent, fiber fracture was observed during fatigue. However, fiber fracture was believed to occur near the final stage of fatigue failure. In fatigued specimens, facet-type fracture appearance was characteristic of matrix fracture morphology. Theoretical modeling of the fatigue behavior of Ti/SCS-6 composites is presented in Part II of this series of articles.

Materials characterization of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites: Part II. Theoretical modeling of fatigue behavior

Flexural fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-ply, continuous silicon carbide (SiC) fibers. The titanium composites had an eightply (0, 90, +45, -45 deg) symmetric layup. Mechanistic investigation of the fatigue behavior is presented in Part I of this series. In Part II, theoretical modeling of the fatigue behavior was performed using finite element techniques to predict the four stages of fatigue deflection behavior. On the basis of the mechanistic understanding, the fiber and matrix fracture sequence was simulated from ply to ply in finite element modeling. The predicted fatigue deflection behavior was found to be in good agreement with the experimental results. Furthermore, it has been shown that the matrix crack initiation starts in the 90 deg ply first, which is in agreement with the experimental observation. Under the same loading condition, the stress in the 90 deg ply of the transverse specimen is greater than that of the longitudinal specimen. This trend explains why the longitudinal specimen has a longer fatigue life than the transverse specimen, as observed in Part I.

TIME‐DEPENDENT FATIGUE CRACK GROWTH IN TITANIUM METAL MATRIX COMPOSITES

Abstract The interaction of fatigue and creep in a titanium metal matrix composite was studied by employing loading frequencies of 10 Hz (in both air and vacuum environment) and 0.1 Hz with and without hold times (in air) at 500°C. It was shown that, for the same loading frequency, the crack growth rate is lower in vacuum than in air. In an air environment, however, where the influence of load‐related creep and environmental effects exist, it was shown that a decrease in the loading frequency leads to a decrease in the crack growth rate. This behavior is interpreted in terms of the redistribution of fiber and matrix stresses occurring in response to the creep‐related relaxation of matrix stresses. The result of this stress redistribution is the generation of a compressive axial residual stress in the matrix phase in the region of the composite ahead of the crack tip. As the crack bridges the fibers in this region, the release of the matrix residual compressive stress leads to the closure of the matrix fractured surfaces at the crack tip, thus leading to a decrease in the crack tip driving force. To support this concept, experimental measurements of the crack opening displacement at different loading frequencies are presented. In addition, a simple model is proposed to describe the nature of the residual stresses developed in the matrix phase during cyclic loading. Results of this model have been examined using finite element analysis. The influence of time‐dependent effects during a fatigue cycle was, furthermore, investigated by carrying out high frequency fatigue tests on specimens which have been previously subjected to creep deformation. Results of these tests in terms of the crack growth rate and associated crack closure, support the conclusion that a predeformed matrix produces a decrease in the crack growth rate of the corresponding composite.

Fatigue behavior of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites

Flexure fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-poly, continuous silicon carbide (SiC) fibers. The Ti/SCS-6 composites had an 8-ply, (0{degree}, 90{degree}, +45{degree}, {minus}45{degree}), symmetric lay-up. During fatigue testing, four stages of flexure deflection behavior were observed. The deflection at stage 1 increased slightly with fatigue cycling, while that at stage 2 increased significantly with cycling. Interestingly, the deflection at stage 3 again increased negligibly with fatigue cycling. Stage 4 was associated with final failure, and the deflection increased abruptly. In the stage 1 region of the deflection behavior, no cracks were observed, the Ti/SiC interface debonding could be present, and the deflection changed slightly with cycling. When the stage 2 region commenced, cracks began to initiate. As stage 2 progressed, both crack density and crack length increased. The increased crack density and crack length contributed to the great increase in the deflection during stage 2. In stage 3, significant crack deflection and branching, and fiber bridging occurred, and crack density remained relatively constant. Crack deflection and branching, and fiber bridging slowed down crack driving force, and little crack extension was observed, which resulted in an insignificant amount of increase in the stage 3 deflection.more » The breakage of fibers in stage 4 significantly increased deflection.« less

A new criterion for determining the failure of Ti/SiC metal-matrix composites

The failure of titanium metal-matrix composites (MMCs) strengthened with monofilament carbon-coated sigma SiC fibres has been studied following exposure at a temperature of 900‡C. Statistical analysis of the data shows that the time to penetration of the carbon layer on the as-received carbon-coated sigma monofilament (SiC+C) can be used as a failure criterion for these composites. The same technique can also be used as a measure of the effectiveness of different diffusion barrier coatings.

Damage development in titanium metal-matrix composites subjected to cyclic loading

Several layups of SCS-6/Ti-15-3 composites were investigated. Fatigue tests were conducted and analyzed for both notched and unnotched specimens at room temperature and elevated temperatures. Thermo-mechanical fatigue results were analyzed. Test results indicated that the stress in the 0 degree fibers is the controlling factor in fatigue life. The static and fatigue strength of these materials is shown to be strongly dependent on the level of residual stresses and the fiber/matrix interfacial strength. Fatigue tests of notched specimens showed that cracks can initiate and grow many fiber spacings in the matrix materials without breaking fibers. Fiber bridging models were applied to characterize the crack growth behavior. The matrix cracks are shown to significantly reduce the residual strength of notched composites. The notch strength of these composites was accurately predicted using a micromechanics based methodology.

Tensile fracture behavior of notched fiber reinforced titanium metal matrix composite

The static fracture behavior of a titanium based metal matrix composite (MMC) with a central hole or a straight notch was investigated. The MMC used was SCS-6/Ti-β21-S with a quasi-isotropic lay-up. Different sizes of hole or notch were used which provided cut-out size to specimen width ratios from 0·1 to 0·4. Two test temperatures were used: ambient and 650°C. At both temperatures, the tested MMC showed a mild hole size effect or notch sensitivity. The failure mechanisms involved the debonding of fibers followed by failure of fibers, and then by failure of the matrix.

Thermo-mechanical fatigue behavior of a cross-ply SCS-6/Ti-15-3 metal-matrix composite: Mall, S. and Schubbe, J.J. Compos. Sci. Technol. (Jan 1994) 50(1), 49–57

Fatigue life modeling of titanium-based metal-matrix composites (MMCs) was accomplished by combining a unified viscoplastic theory, a non-linear micromechanics analysis and a damage accumulation model. The micromechanics analysis employed the Bodner-Partom unified viscoplastic theory with directional hardening. This analysis was then combined with a life-fraction fatigue model to account for the time-dependent component of fatigue damage. The life-fraction fatigue model involved the linear summation of damage from the fiber and matrix constituents of the composite. A single set of empirical constants for the life-fraction fatigue model were established for each of two titanium MMCs reinforced with silicon carbide fibers: SCS-6/Ti-15-3 and SCS-6/ TIMETAL®21s. The predicted fatigue lives were within one order of magnitude of the experimental data for different loading conditions: isothermal fatigue, and both in-phase and out-of-phase thermomechanical fatigue. MMCs modeled included cross-ply, quasi-isotropic and unidirectional SCS-6/TIMETAL®21s, and cross-ply and quasi-isotropic SCS-6/Ti-15-3 laminates.

AES and RBS characterization of titanium silicide bilayers on SiC

physica status solidi (a)Volume 139, Issue 1 p. K39-K44 Surfaces, Interfaces, Thin Films; Lower-Dimensional Systems AES and RBS characterization of titanium silicide bilayers on SiC K. Bilba, K. Bilba Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. P. Manaud, J. P. Manaud Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. M. Quenisset, J. M. Quenisset Laboratoire de Chimie du Solide, Talence Search for more papers by this authorY. Lepetitcorps, Y. Lepetitcorps Laboratoire de Chimie du Solide, Talence Search for more papers by this author K. Bilba, K. Bilba Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. P. Manaud, J. P. Manaud Laboratoire de Chimie du Solide, Talence Search for more papers by this authorJ. M. Quenisset, J. M. Quenisset Laboratoire de Chimie du Solide, Talence Search for more papers by this authorY. Lepetitcorps, Y. Lepetitcorps Laboratoire de Chimie du Solide, Talence Search for more papers by this author First published: 16 September 1993 https://doi.org/10.1002/pssa.2211390134Citations: 2 351 cours de la Libération. F-33405 Talence Cedex, France. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume139, Issue116 September 1993Pages K39-K44 RelatedInformation

An investigation into thermomechanical fatigue of metal matrix composites: Karayaka, M. Diss. Abstr. Int. July 1992 53 (1) 191pp

Fatigue life modeling of titanium-based metal-matrix composites (MMCs) was accomplished by combining a unified viscoplastic theory, a non-linear micromechanics analysis and a damage accumulation model. The micromechanics analysis employed the Bodner-Partom unified viscoplastic theory with directional hardening. This analysis was then combined with a life-fraction fatigue model to account for the time-dependent component of fatigue damage. The life-fraction fatigue model involved the linear summation of damage from the fiber and matrix constituents of the composite. A single set of empirical constants for the life-fraction fatigue model were established for each of two titanium MMCs reinforced with silicon carbide fibers: SCS-6/Ti-15-3 and SCS-6/ TIMETAL®21s. The predicted fatigue lives were within one order of magnitude of the experimental data for different loading conditions: isothermal fatigue, and both in-phase and out-of-phase thermomechanical fatigue. MMCs modeled included cross-ply, quasi-isotropic and unidirectional SCS-6/TIMETAL®21s, and cross-ply and quasi-isotropic SCS-6/Ti-15-3 laminates.

Damage development in titanium metal matrix composites subjected to cyclic loading: Johnson,W.S. N92-23422/5/XAB (1992) 25 pp

Damage development in titanium metal matrix composites subjected to cyclic loading: Johnson,W.S. N92-23422/5/XAB (1992) 25 pp

Metal- matrix composite processing technologies for aircraft engine applications

Titanium metal-matrix composites (MMC) are prime candidate materials for aerospace applications be-cause of their excellent high-temperature longitudinal strength and stiffness and low density compared with nickel- and steel-base materials. This article examines the steps GE Aircraft Engines (GEAE) has taken to develop an induction plasma deposition (IPD) processing method for the fabrication of Ti6242/SiC MMC material. Information regarding process methodology, microstructures, and mechani-cal properties of consolidated MMC structures will be presented. The work presented was funded under the GE-Aircraft Engine IR & D program.

Micromodelling of effective stress intensities for bridged cracks in fibre-reinforced titanium metal-matrix composites

Weight function methods have been used to model and assess the crack growth resistance of fibre-reinforced composite materials. Many trends in observed crack growth resistance behaviour in the presence of crack bridging can be predicted accurately. For the case of single dominant cracks the application of fracture mechanics parameters to characterize crack growth appears to be appropriate. In particular the model can predict accurately crack growth rates in near crack arrest regions, together with the onset of crack arrest. Effects of unbridged crack length, volume fraction of fibres and fibre failure on crack growth rates have all been predicted.

Damage development in titanium metal-matrix composites subjected to cyclic loading

For several lay-ups of SCS-6/Ti-15-3 composites fatigue tests were conducted and analysed for both notched and unnotched specimens at room and elevated temperatures. Thermomechanical fatigue results were also analysed. Test results indicated that the stress in the 0° fibres is the controlling factor in fatigue life. The static and fatigue strengths of these materials are shown to be strongly dependent on the level of residual stresses and the fibre/matrix interfacial strength. Fatigue tests of notched specimens showed that cracks can initiate and grow many fibre spacings in the matrix material without breaking the fibres. Fibre bridging models were applied to characterize the crack growth behaviour. The matrix cracks are shown to reduce significantly the residual strength of notched composites. The notched strength of these composites was accurately predicted using a micromechanics-based methodology.

Microstructural analysis of isothermally exposed Ti/SiC metal matrix composites

Specimens of diffusion-bonded titanium metal matrix composites have been subjected to thermal exposure treatments and examined principally by transmission electron microscopy. The fibres investigated were SCS-6™ and Sigma™. The fibre/matrix reaction layers have been shown to consist of titanium carbide and two titanium silicides. The reaction proceeds by the initial formation of a layer of TiC followed by a layer of mixed silicides, Ti5Si4 and Ti5Si3. Extensive porosity is generated during the reaction and this prevents the formation of a completely protective interfacial layer.

Low Pressure Induction Plasma Spraying of Titanium Metal Matrix Composites SCS-6/Ti6Al-4V and SCS-6/Ti6Al-2Sn-4Zr-2Mo

Two titanium metal matrix composites (MMC's) have been successfully fabricated from low pressure induction plasma sprayed monotape and their mechanical behavior has been characterized. Powders of Ti6Al-4V (Ti6–4) and Ti6Al-2Sn-4Zr-2Mo (Ti6-2-4-2) were used as matrix sources and the reinforcement was Textron Specialty Materials (TSM) SCS-6 silicon carbide fiber. The importance of process control to minimize interstitial (O, N, H and C) contamination effects is discussed. Oxygen pick-ups were reduced to typically less than 200 ppm and total interstitial pick-up levels were in the range of 200–500 ppm. Uniaxially reinforced composite panels of 4-ply construction were fabricated from these monotape materials by the HIP process and tension tests in the fiber direction were performed. Tensile strengths and elastic moduli averaged 1565 MPa (227 KSI) and 182 GPa (26.4 MSI) for the SCS-6/Ti6-4; and 1531 MPa (222 KSI) and 184 GPa (26.7 MSI) for the SCS-6/Ti6-2-4-2 for composite fiber volume fractions of 0.27 – 0.28 and 0.29 – 0.30, respectively. The results compared favorably with other fabrication approaches for these composite systems and with rule-of-mixture (ROM) predictions. It was concluded that SCS-6/titanium composites fabricated from plasma sprayed monotapes exhibit properties consistent with state-of-the-art MMC fabrication technology.

Method to produce titanium metal matrix composites with improved fracture and creep resistance: Eylon, D. and Froes, F.H. (The Secretary of the Air Force, Washington, DC, USA) US Pat 4 822 432 (18 April 1989)

Method to produce titanium metal matrix composites with improved fracture and creep resistance: Eylon, D. and Froes, F.H. (The Secretary of the Air Force, Washington, DC, USA) US Pat 4 822 432 (18 April 1989)