Tensile Creep

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Takahiko Sagawa - One of the best experts on this subject based on the ideXlab platform.

  • temperature dependence of off axis Tensile Creep rupture behavior of a unidirectional carbon epoxy laminate
    Composites Part A-applied Science and Manufacturing, 2008
    Co-Authors: Masamichi Kawai, Takahiko Sagawa
    Abstract:

    Abstract Stress-time-temperature extrapolation of off-axis Creep rupture data on a T800H/2500 unidirectional carbon/epoxy laminate is studied. Off-axis Tensile Creep rupture tests are performed on plain coupon specimens with five kinds of fiber orientations θ  = 0, 10, 30, 45 and 90° at each of the test temperatures of 60, 80 and 130 °C, respectively, within the time range up to 10 h. Creep rupture of unidirectional specimens takes place predominantly along the fibers in a brittle manner, regardless of the fiber orientation and test temperature. Straight lines can be fitted well to the log–log plots of Creep stress level against the time to rupture over the restricted range of time for all fiber orientations, regardless of the test temperature. Those fitted straight lines for different fiber orientations at each test temperature are almost parallel to each other, and they are approximately extrapolated to the stress levels nearly equal to the off-axis Tensile strengths at the test temperature. The fiber orientation dependence of the off-axis Creep rupture data obtained at each test temperature can approximately be removed by normalizing the Creep stress levels with the help of the off-axis Tensile strengths, which allows identification of a single fiber-orientation-independent master Creep rupture curve for each test temperature. The effect of temperature on Creep strength is reflected by the change in slope of the normalized master Creep rupture curve. For predicting the off-axis Creep rupture lives at different stress levels and temperatures, two kinds of new and efficient engineering methods are developed. One method is based on a formula derived from a modified damage mechanics model for Creep rupture. The other one is formulated on the basis of a grand master Creep rupture curve built by means of a non-dimensional effective stress and the Larson–Miller parameter. The proposed damage mechanics and grand master curve approaches are validated in respect of accuracy of prediction of the off-axis Creep rupture lives of the unidirectional carbon/epoxy composite at different stress levels over a range of temperatures.

  • off axis Tensile Creep rupture behavior of a unidirectional cfrp laminate at high temperatures
    Transactions of the Japan Society of Mechanical Engineers. A, 2008
    Co-Authors: Masamichi Kawai, Takahiko Sagawa
    Abstract:

    Creep rupture behavior of a unidirectional carbon/epoxy T800H/Epoxy Laminate under constant off-axis loading conditions at different temperatures of 60, 100 and 130°C is examined. Tensile Creep rupture tests are performed on plain coupon specimens with different fiber orientations θ=0, 10, 30, 45 and 90°. Creep rupture of specimens takes place predominantly along reinforcing fibers is a brittle manner, regardless of the fiber orientation. The log-log plots of the Creep rupture data can approximately be described using straight lines with negative slopes over the range of rupture time up to 10h, regardless of the fiber orientation. Then, two kinds of simple phenomenological models are developed for predicting the time-to-failure of unidirectional composites. Validities of those models are evaluated by comparing with experimental results. It is demonstrated that the proposed models succeed in adequately predicting the Creep rupture lives of the unidirectional composite at different temperatures.

  • off axis Tensile Creep rupture of unidirectional cfrp laminates at elevated temperature
    Composites Part A-applied Science and Manufacturing, 2006
    Co-Authors: Masamichi Kawai, Y Masuko, Takahiko Sagawa
    Abstract:

    Abstract Off-axis Tensile Creep fracture behavior of unidirectional carbon/epoxy T800H/Epoxy laminates is studied at 100 °C under constant load conditions. Off-axis Creep rupture data on plain coupon specimens are obtained within the time range up to 10 h for four kinds of off-axis fiber orientations. The log–log plots of the Creep stress against the rupture time can approximately be described by straight lines with negative slopes over the range of Creep life for all the fiber orientations. The static Tensile strengths extrapolated from those straight lines almost agree with the experimental results for respective fiber orientations. The Creep rupture data normalized with respect to the static strength approximately falls on a single Creep rupture curve. These observations suggest that the fiber orientation dependence of Creep rupture strength is similar to that of static Tensile strength. The Creep fracture occurs along reinforcing fibers in a brittle manner without accompanying the appreciable secondary and tertiary Creep stages, regardless of the fiber orientations, and thus the off-axis Creep deformation prior to fracture is characterized by the primary Creep stage for all the fiber orientations. Then, a phenomenological model for the Creep deformation and rupture behaviors of the unidirectional composite is developed, with a view to making preliminary predictions of Creep life from a limited amount of data. It is demonstrated that the proposed model can moderately describe the observed features of the Creep deformation and Creep rupture behaviors under off-axis loading conditions.

Masamichi Kawai - One of the best experts on this subject based on the ideXlab platform.

  • temperature dependence of off axis Tensile Creep rupture behavior of a unidirectional carbon epoxy laminate
    Composites Part A-applied Science and Manufacturing, 2008
    Co-Authors: Masamichi Kawai, Takahiko Sagawa
    Abstract:

    Abstract Stress-time-temperature extrapolation of off-axis Creep rupture data on a T800H/2500 unidirectional carbon/epoxy laminate is studied. Off-axis Tensile Creep rupture tests are performed on plain coupon specimens with five kinds of fiber orientations θ  = 0, 10, 30, 45 and 90° at each of the test temperatures of 60, 80 and 130 °C, respectively, within the time range up to 10 h. Creep rupture of unidirectional specimens takes place predominantly along the fibers in a brittle manner, regardless of the fiber orientation and test temperature. Straight lines can be fitted well to the log–log plots of Creep stress level against the time to rupture over the restricted range of time for all fiber orientations, regardless of the test temperature. Those fitted straight lines for different fiber orientations at each test temperature are almost parallel to each other, and they are approximately extrapolated to the stress levels nearly equal to the off-axis Tensile strengths at the test temperature. The fiber orientation dependence of the off-axis Creep rupture data obtained at each test temperature can approximately be removed by normalizing the Creep stress levels with the help of the off-axis Tensile strengths, which allows identification of a single fiber-orientation-independent master Creep rupture curve for each test temperature. The effect of temperature on Creep strength is reflected by the change in slope of the normalized master Creep rupture curve. For predicting the off-axis Creep rupture lives at different stress levels and temperatures, two kinds of new and efficient engineering methods are developed. One method is based on a formula derived from a modified damage mechanics model for Creep rupture. The other one is formulated on the basis of a grand master Creep rupture curve built by means of a non-dimensional effective stress and the Larson–Miller parameter. The proposed damage mechanics and grand master curve approaches are validated in respect of accuracy of prediction of the off-axis Creep rupture lives of the unidirectional carbon/epoxy composite at different stress levels over a range of temperatures.

  • off axis Tensile Creep rupture behavior of a unidirectional cfrp laminate at high temperatures
    Transactions of the Japan Society of Mechanical Engineers. A, 2008
    Co-Authors: Masamichi Kawai, Takahiko Sagawa
    Abstract:

    Creep rupture behavior of a unidirectional carbon/epoxy T800H/Epoxy Laminate under constant off-axis loading conditions at different temperatures of 60, 100 and 130°C is examined. Tensile Creep rupture tests are performed on plain coupon specimens with different fiber orientations θ=0, 10, 30, 45 and 90°. Creep rupture of specimens takes place predominantly along reinforcing fibers is a brittle manner, regardless of the fiber orientation. The log-log plots of the Creep rupture data can approximately be described using straight lines with negative slopes over the range of rupture time up to 10h, regardless of the fiber orientation. Then, two kinds of simple phenomenological models are developed for predicting the time-to-failure of unidirectional composites. Validities of those models are evaluated by comparing with experimental results. It is demonstrated that the proposed models succeed in adequately predicting the Creep rupture lives of the unidirectional composite at different temperatures.

  • off axis Tensile Creep rupture of unidirectional cfrp laminates at elevated temperature
    Composites Part A-applied Science and Manufacturing, 2006
    Co-Authors: Masamichi Kawai, Y Masuko, Takahiko Sagawa
    Abstract:

    Abstract Off-axis Tensile Creep fracture behavior of unidirectional carbon/epoxy T800H/Epoxy laminates is studied at 100 °C under constant load conditions. Off-axis Creep rupture data on plain coupon specimens are obtained within the time range up to 10 h for four kinds of off-axis fiber orientations. The log–log plots of the Creep stress against the rupture time can approximately be described by straight lines with negative slopes over the range of Creep life for all the fiber orientations. The static Tensile strengths extrapolated from those straight lines almost agree with the experimental results for respective fiber orientations. The Creep rupture data normalized with respect to the static strength approximately falls on a single Creep rupture curve. These observations suggest that the fiber orientation dependence of Creep rupture strength is similar to that of static Tensile strength. The Creep fracture occurs along reinforcing fibers in a brittle manner without accompanying the appreciable secondary and tertiary Creep stages, regardless of the fiber orientations, and thus the off-axis Creep deformation prior to fracture is characterized by the primary Creep stage for all the fiber orientations. Then, a phenomenological model for the Creep deformation and rupture behaviors of the unidirectional composite is developed, with a view to making preliminary predictions of Creep life from a limited amount of data. It is demonstrated that the proposed model can moderately describe the observed features of the Creep deformation and Creep rupture behaviors under off-axis loading conditions.

Gregory N. Morscher - One of the best experts on this subject based on the ideXlab platform.

  • Tensile Creep and rupture of 2d woven sic sic composites for high temperature applications
    Journal of The European Ceramic Society, 2010
    Co-Authors: Gregory N. Morscher
    Abstract:

    The Tensile Creep and rupture behavior of 2D-woven SiC fiber-reinforced SiC matrix composites with potential for advanced high temperature structural applications was determined in air at 1315 °C. The results are compared to similar SiC/SiC data in the literature in order to understand the underlying Creep and rupture mechanisms. Focus was placed on three different near-stoichiometric SiC fiber-types and three SiC-based matrix systems produced by different process routes. In general, the Creep and rupture properties of the tested composites were primarily dictated by the Creep resistance of the fiber-type, with the Sylramic-iBN fiber typically showing the best behavior. However, the type of matrix did have an effect on the composite Creep and rupture lives due to load-sharing differences for the different matrix types and due to stoichiometry in the case of chemical vapor infiltration SiC matrices.

  • Tensile Creep and fatigue of sylramic ibn melt infiltrated sic matrix composites retained properties damage development and failure mechanisms
    Composites Science and Technology, 2008
    Co-Authors: Gregory N. Morscher, Jalees Ahmad, Unni Santhosh, Greg Ojard, Yasser Gowayed, Robert Miller, Reji John
    Abstract:

    Abstract An understanding of the elevated temperature Tensile Creep, fatigue, rupture, and retained properties of ceramic matrix composites (CMC) envisioned for use in gas turbine engine applications is essential for component design and life-prediction. In order to quantify the effect of stress, time, temperature, and oxidation for a state-of-the-art composite system, a wide variety of Tensile Creep, dwell fatigue, and cyclic fatigue experiments were performed in air at 1204 °C for the SiC/SiC CMC system consisting of Sylramic-iBN SiC fibers, BN fiber interphase coating, and slurry-cast melt-infiltrated (MI) SiC-based matrix. Tests were either taken to failure or interrupted. Interrupted tests were then mechanically tested at room temperature to determine the residual properties. The retained properties of most of the composites subjected to Tensile Creep or fatigue were usually within 20% of the as-produced strength and 10% of the as-produced elastic modulus. It was observed that during Creep, residual stresses in the composite are altered to some extent which results in an increased compressive stress in the matrix upon cooling and a subsequent increased stress required to form matrix cracks. Microscopy of polished sections and the fracture surfaces of specimens which failed during stressed-oxidation or after the room-temperature retained property test was performed on some of the specimens in order to quantify the nature and extent of damage accumulation that occurred during the test. It was discovered that the distribution of stress-dependent matrix cracking at 1204 °C was similar to the as-produced composites at room temperature; however, matrix crack growth occurred over time and typically did not appear to propagate through-the-thickness except at the final failure crack. Failure of the composites was due to either oxidation-induced unbridged crack growth, which dominated the higher stress regime (⩾179 MPa) or controlled by degradation of the fibers, probably caused by intrinsic Creep-induced flaw growth of the fibers or internal attack of the fibers via Si diffusion through the CVI SiC and/or microcracks at the lower stress regime (⩽165 MPa).

  • Creep and stress strain behavior after Creep for sic fiber reinforced melt infiltrated sic matrix composites
    Journal of the American Ceramic Society, 2006
    Co-Authors: Gregory N. Morscher, Vijay V Pujar
    Abstract:

    Silicon carbide fiber (Hi-Nicalon Type S, Nippon Carbon) reinforced silicon carbide matrix composites containing melt-infiltrated silicon were subjected to Creep at 1315°C at three different stress conditions. For the specimens that did not rupture after 100 h of Tensile Creep, fast-fracture experiments were performed immediately following the Creep test at the Creep temperature (1315°C) or after cooling to room temperature. All specimens demonstrated excellent Creep resistance and compared well to the Creep behavior published in the literature on similar composite systems. Tensile results on the after-Creep specimens showed that the matrix cracking stress actually increased, which is attributed to stress redistribution between composite constituents during Tensile Creep.

  • comparison of bend stress relaxation and Tensile Creep of cvd sic fibers
    Journal of the American Ceramic Society, 1995
    Co-Authors: Gregory N. Morscher, Charles A Lewinsohn, Charles E Bakis, R E Tressler, Timothy Wagner
    Abstract:

    Three different CVD SiC fibers were tested for bend stress relaxation (BSR) and Tensile Creep over a wide range of temperatures, times, and stresses. Primary Creep was always observed, even for Creep strains on the order of 2%. The BSR and Tensile Creep results were compared using simple linear viscoelastic principles. It was found that BSR results could predict the same time and temperature dependence as Tensile Creep; however, BSR-predicted Creep strains usually overestimated the magnitude of Tensile Creep strain. The time, temperature, and stress dependence were determined for all the fibers for the experimental conditions of this study. Some of the primary Creep behavior can be explained by load-sharing effects between the core and the CVD SiC substrate and some microstructural changes; however, the extent of primary Creep cannot fully be accounted for from this work.

Sheldon M Wiederhorn - One of the best experts on this subject based on the ideXlab platform.

  • Tensile Creep of coarse grained ti3sic2 in the 1000 1200 c temperature range
    Journal of Alloys and Compounds, 2003
    Co-Authors: Miladin Radovic, Michel W Barsoum, T Elraghy, Sheldon M Wiederhorn
    Abstract:

    Abstract The Tensile Creep of coarse-grained, CG, Ti3SiC2 samples, in the 1000–1200 °C temperature, T, and 10 MPa to 100 MPa stress, σ, ranges, respectively, was studied. The Creep behavior is characterized by three regimes: an initial, a secondary where the Creep rate is at a minimum, e min , and a tertiary regime. In the intermediate regime e min is given by: e min ( s −1 )=e o exp 17±1 σ σ o 2.0±0.1 exp −458±12 kJ/mol RT where σ0=1 MPa and e0=1 s−1. The times to failure are given by: tf (s)=exp(−2±0.3) e min −1 . The results presented herein confirm that: (a) dislocation Creep is the dominant mechanism; (b) the high plastic anisotropy of Ti3SiC2 results in large internal stresses during Creep; (c) the response is dictated by a competition between the rates of generation and dissipation of these internal stresses; (d) at higher temperatures and/or lower strain rates the internal stresses can dissipate and the behavior is more ductile. Furthermore, in the tertiary Creep regime, the Creep appears to occur by a combination of dislocation Creep and the formation of cavities and cracks. The coarse-grained samples have lower Creep rates than their fine-grained (3–5 μm) counterparts, and their times to failure are longer. The latter is partially attributable to the ability of the larger grains, whose basal planes are normal to the applied load, to form tenacious crack bridges by delamination and kink band formation, in addition to the bridges that occur when the basal planes are parallel to the applied load.

  • Tensile Creep of fine grained 3 5 μm ti3sic2 in the 1000 1200 c temperature range
    Acta Materialia, 2001
    Co-Authors: Miladin Radovic, Michel W Barsoum, T Elraghy, Sheldon M Wiederhorn
    Abstract:

    Abstract In this paper we report on the Tensile Creep behavior of fine-grained (3–5 μm) Ti3SiC2 in the 1000–1200°C temperature, T, range and the 10–100 MPa stress, σ, range. The Creep behavior is characterized by three regimes a primary, quasi-steady state and a tertiary. In the quasi-steady state range and over the entire range of testing temperatures and stresses, the minimum Creep rate, e min , is given by: e min ( s −1 )= e 0 · exp [19±1]·(σ/σ 0 ) 1.5±0.1 · exp (−445±10) kJ/mol RT where σ0=MPa and e 0 =1 s−1. The times to failure, tf, were fitted to an expression of the form: t f (s)=t 0 · exp [−2±1]·[ e min / e 0 ] −0.9±0.1 where t0=1 s. Interrupted Creep tests show that volume-conserving plastic deformation is the dominant source of strain during the secondary Creep regime, while cavities and microcracks are responsible for the acceleration of the Creep rate during the tertiary Creep regime. Like in ice, large internal stresses, especially at high stresses, are developed in Ti3SiC2 during deformation, as a consequence of its extreme plastic anisotropy. The response of Ti3SiC2 to stress appears to be determined by a competition between the rates of accumulation and relaxation of these internal stresses.

  • cavitation contributes substantially to Tensile Creep in silicon nitride
    Journal of the American Ceramic Society, 1995
    Co-Authors: William E Luecke, Sheldon M Wiederhorn, Bernard J Hockey, Ralph F Krause, Gabrielle G Long
    Abstract:

    During Tensile Creep of a hot isostatically pressed (HIPed) silicon nitride, the volume fraction of cavities increases linearly with strain; these cavities produce nearly all of the measured strain. In contrast, compressive Creep in the same stress and temperature range produces very little cavitation. A stress exponent that increases with stress ({dot {var_epsilon}} {proportional_to} {sigma}{sup n}, 2 < n < 7) characterizes the Tensile Creep response, while the compressive Creep response exhibits a stress dependence of unity. Furthermore, under the same stress and temperature, the material Creeps nearly 100 times faster in tension than in compression. Transmission electron microscopy (TEM) indicates that the cavities formed during Tensile Creep occur in pockets of residual crystalline silicate phase located at silicon nitride multigrain junctions. Small-angle X-ray scattering (SAXS) from crept material quantifies the size distribution of cavities observed in TEM and demonstrates that cavity addition, rather than cavity growth, dominates the cavitation process. These observations are in accord with a model for Creep based on the deformation of granular materials in which the microstructure must dilate for individual grains t slide past one another. During Tensile Creep the silicon nitride grains remain rigid; cavitation in the multigrain junctions allows the silicate tomore » flow from cavities to surrounding silicate pockets, allowing the dilation of the microstructure and deformation of the material. Silicon nitride grain boundary sliding accommodates this expansion and leads to extension of the specimen. In compression, where cavitation is suppressed, deformation occurs by solution-reprecipitation of silicon nitride.« less

Alessandro Pegoretti - One of the best experts on this subject based on the ideXlab platform.

  • Tensile Creep behaviour of polymethylpentene silica nanocomposites
    Polymer International, 2010
    Co-Authors: Andrea Dorigato, Alessandro Pegoretti
    Abstract:

    For the first time, poly(4-methyl-1-pentene) (PMP) nanocomposites were prepared by melt compounding 2 vol% of fumed silica nanoparticles, in order to study the role of the nanofiller surface area and functionalization on the Tensile mechanical response of the material, with particular focus on its Creep behaviour. The high optical transparency of the polymer matrix was substantially preserved in the nanocomposites, while the mechanical properties (in particular the Creep stability) were improved. Dynamic mechanical thermal analysis showed an improvement of the storage modulus, more evident above the glass transition temperature of the polymer matrix. Uniaxial Tensile tests evidenced that the elastic modulus of the material was positively affected by the presence of silica nanoparticles, even if a slight reduction of the strain at break was detected. The reduction of the Tensile Creep compliance was proportional to the surface area of the nanofiller, being more evident at high stresses and elevated temperatures. Findley's law furnished a satisfactory fitting of the Creep behaviour of the composites, even at high temperatures. It clearly emerges that the incorporation of fumed silica nanoparticles in PMP can be an effective way to overcome the problem of the poor Creep stability of polyolefins, especially at high temperatures and high stresses. Moreover the possibility of retaining the original transparency of the material is fundamental for the production of completely transparent PMP components. Copyright © 2010 Society of Chemical Industry

  • non linear Tensile Creep of polypropylene time strain superposition and Creep prediction
    Polymer, 2006
    Co-Authors: Jan Kolařik, Alessandro Pegoretti
    Abstract:

    Abstract In most practical applications, isothermal compliance of polymeric materials depends on both time and stress so that their non-linear viscoelastic behavior is of primary importance. A concept is adopted that the non-linearity of Tensile Creep is mainly brought about by the strain-induced increment of the free volume (in materials with Poisson ratio smaller than 0.5). Consequently, the traditional stress-strain linearity limit can be viewed as an artificial limit related to limited accuracy of the measurements at low stresses and strains. The internal time—Tensile compliance superposition of non-linear Creep data is applied to construct a generalized compliance curve, which corresponds to a pseudo iso-free-volume state. The superposition of compliance curves obtained at different stresses requires shift factors along the time axis calculated a priori for individual data points. As the generalized curve can be generated by means of short-term Creeps, the proposed procedure offers essential savings of experimental time. A most practical outcome of the outlined format is that the generalized dependence can be employed for predicting the real time-dependent compliance for any stress in the range of reversible strains. The results indicate that the compliance of PPs decreases with their crystallinity, while their Creep rates are almost identical. Only rubber-toughened PP does show a slightly higher Creep rate, which is attributed to the ‘softening’ effect of rubber particles in the PP matrix.