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Masamichi Kawai - One of the best experts on this subject based on the ideXlab platform.
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probabilistic anisomorphic constant fatigue life diagram approach for prediction of p s n curves for woven carbon epoxy Laminates at any stress ratio
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Masamichi Kawai, K YanoAbstract:Abstract A general engineering methodology to construct a family of anisomorphic constant fatigue life (CFL) diagrams with probability of failure as the parameter that allows efficiently predicting P–S–N curves at any stress ratios is developed and validated for a plain weave fabric carbon/epoxy Laminate. Constant amplitude fatigue tests are first performed to obtain statistical samples of fatigue life at different stress levels and stress ratios, respectively. Static tensile and compressive strength data are also collected. The Kolmogorov–Smirnov and Anderson–Darling goodness-of-fit tests suggest that both two-parameter lognormal and Weibull distributions are acceptable as the distributions for the static strength and fatigue life data, respectively, at the significance level of 5%. Then, we attempt to develop a methodology for efficient construction of the anisomorphic CFL diagrams for different constant values of probability of failure. It requires the P–S–N curves for any percentile points of the distribution for the critical stress ratio. To come up with this requirement, a probabilistic scaling law is formulated. It takes account of the probability-of-failure dependence of the critical stress ratio and the stress-ratio dependence of the P–S–N curve for the critical stress ratio. Finally, the anisomorphic CFL diagrams for different constant values of probability of failure are predicted using the proposed methodology, and they are shown to be in good agreement with the experimental results. It is also demonstrated that the P–S–N curves can efficiently and accurately be predicted for the woven CFRP Laminate at any stress ratios using the proposed probabilistic anisomorphic CFL diagram approach.
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a failure mode based anisomorphic constant life diagram for a unidirectional carbon epoxy Laminate under off axis fatigue loading at room temperature
Journal of Composite Materials, 2014Co-Authors: Masamichi Kawai, N ItohAbstract:The off-axis constant fatigue life diagrams for a unidirectional carbon/epoxy Laminate in different fiber orientations are identified over the whole range of stress ratio. The experimental results show that the off-axis constant fatigue life diagram plotted in the plane of alternating and mean stresses tends to shrink and incline to the left of the alternating stress axis more significantly as the off-axis angle of a specimen increases. The overall shapes of the off-axis constant fatigue life envelopes for different constant values of life are highly non-linear and asymmetric about the alternating stress axis, regardless of fiber orientation. These observations suggest that the sensitivity to mean stress in off-axis fatigue differs depending on the mode of fatigue loading, i.e. tension–tension, tension–compression, and compression–compression loading, and the difference is associated with the different modes of failure under different modes of fatigue loading. To deal with the off-axis fatigue strength of...
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a multiaxial fatigue failure criterion based on the principal constant life diagrams for unidirectional carbon epoxy Laminates
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: Masamichi Kawai, T TeranumaAbstract:Abstract A new fatigue failure criterion for unidirectional composites has been developed on the basis of the modified Tsai-Hill static failure criterion that can distinguish between the static strengths in tension and compression. A new idea is to calculate the principal fatigue strengths involved by the fatigue failure criterion using the associated constant fatigue life (CFL) diagrams. First, the in-plane principal CFL diagrams for a unidirectional carbon/epoxy Laminate in longitudinal, transverse and in-plane shear loading conditions are identified by experiment. Then, the four-segment anisomorphic CFL diagram approach, which was developed in an earlier study, is shown to be applicable in accurate description of all of the principal CFL diagrams that are highly nonlinear and asymmetric in shape. Finally, it is demonstrated that the off-axis S–N relationship for the unidirectional carbon/epoxy Laminate can accurately and efficiently be predicted for any stress ratio and any fiber orientation using the proposed fatigue life prediction methodology.
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a general method for predicting temperature dependent anisomorphic constant fatigue life diagram for a woven fabric carbon epoxy Laminate
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: Masamichi Kawai, Y Matsuda, R YoshimuraAbstract:Abstract The anisomorphic constant fatigue life (CFL) diagram approach to prediction of fatigue lives of composites, which was developed in an earlier study, is developed further into a more general methodology that can deal with the mean stress sensitivity in fatigue of composites at different temperatures. The temperature dependence of the anisomorphic CFL diagram for a given composite is characterized by the temperature dependence of the static strengths in tension and compression and of the reference S–N relationship for a critical stress ratio. The temperature dependence of the static strengths in tension and compression is first formulated to describe the temperature dependence of the critical stress ratio. To predict the reference S–N relationships at different temperatures, the change in the value of critical stress ratio with temperature as well as the effect of temperature on fatigue should be taken into account. To this end, a new and efficient engineering method is developed which is based on a grand master S–N curve built by means of a modified fatigue strength ratio and a life-temperature parameter of the Larson–Miller type. The generalized anisomorphic CFL diagram approach developed in this study succeeds in efficiently and adequately predicting the CFL diagrams for a woven fabric carbon/epoxy quasi-isotropic Laminate at different temperatures and thus the mean stress dependence of the S–N relationships of the Laminate at different temperatures.
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tension compression asymmetry in the off axis nonlinear rate dependent behavior of a unidirectional carbon epoxy Laminate at high temperature and incorporation into viscoplasticity modeling
Advanced Composite Materials, 2009Co-Authors: Masamichi Kawai, Jianqi Zhang, S Saito, Yi Xiao, H HattaAbstract:Off-axis compressive deformation behavior of a unidirectional CFRP Laminate at high temperature and its strain-rate dependence in a quasi-static range are examined for various fiber orientations. By comparing the off-axis compressive and tensile behaviors at an equal strain rate, the effect of different loading modes on the flow stress level, rate-dependence and nonlinearity of the off-axis inelastic deformation is elucidated. The experimental results indicate that the compressive flow stress levels for relatively larger off-axis angles of 30°,45° and 90° are about 50 percent larger than in tension for the same fiber orientations, respectively. The nonlinear deformations under off-axis tensile and compressive loading conditions exhibit significant strain-rate dependence. Similar features are observed in the fiber-orientation dependence of the off-axis flow stress levels under tension and compression and in the off-axis flow stress differential in tension and compression, regardless of the strain rate. A p...
S Feih - One of the best experts on this subject based on the ideXlab platform.
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tensile properties of carbon fibres and carbon fibre polymer composites in fire
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: S Feih, A P MouritzAbstract:The effect of fire on the tensile properties of carbon fibres is experimentally determined to provide new insights into the tensile performance of carbon fibre-polymer composite materials during fire. Structural tests on Carbon-Epoxy Laminate reveal that thermally-activated weakening of the fibre reinforcement is the dominant softening process which leads to failure in the event of a fire. This process is experimentally investigated by determining the reduction to the tensile properties and identifying the softening mechanism of T700 carbon fibre following exposure to simulated fires of different temperatures (up to 700 degrees C) and atmospheres (air and inert). The fibre modulus decreases with increasing temperature (above similar to 500 degrees C) in air, which is attributed to oxidation of the higher stiffness layer in the near-surface fibre region. The fibre modulus is not affected when heated in an inert (nitrogen) atmosphere due to the absence of surface oxidation, revealing that the stiffness loss of carbon fibre composites in fire is sensitive to the oxygen content. The tensile strength of carbon fibre is reduced by nearly 50% following exposure to temperatures over the range 400-700 degrees C in an air or inert atmosphere. Unlike the fibre modulus, the reduction in fibre strength is insensitive to the oxygen content of the atmosphere during fire. The reduction in strength is possibly attributable to very small (under similar to 100 nm) flaws and removal of the sizing caused by high temperature exposure.
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tensile properties of carbon fibres and carbon fibre polymer composites in fire
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: S Feih, A P MouritzAbstract:Abstract The effect of fire on the tensile properties of carbon fibres is experimentally determined to provide new insights into the tensile performance of carbon fibre–polymer composite materials during fire. Structural tests on carbon–epoxy Laminate reveal that thermally-activated weakening of the fibre reinforcement is the dominant softening process which leads to failure in the event of a fire. This process is experimentally investigated by determining the reduction to the tensile properties and identifying the softening mechanism of T700 carbon fibre following exposure to simulated fires of different temperatures (up to 700 °C) and atmospheres (air and inert). The fibre modulus decreases with increasing temperature (above ∼500 °C) in air, which is attributed to oxidation of the higher stiffness layer in the near-surface fibre region. The fibre modulus is not affected when heated in an inert (nitrogen) atmosphere due to the absence of surface oxidation, revealing that the stiffness loss of carbon fibre composites in fire is sensitive to the oxygen content. The tensile strength of carbon fibre is reduced by nearly 50% following exposure to temperatures over the range 400–700 °C in an air or inert atmosphere. Unlike the fibre modulus, the reduction in fibre strength is insensitive to the oxygen content of the atmosphere during fire. The reduction in strength is possibly attributable to very small (under ∼100 nm) flaws and removal of the sizing caused by high temperature exposure.
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compression fatigue properties of z pinned quasi isotropic carbon epoxy Laminate with barely visible impact damage
Composite Structures, 2011Co-Authors: S Feih, Adrian P. MouritzAbstract:This paper presents an experimental study into the use of z-pins to improve the compression fatigue properties of quasi-isotropic carbon fibre-epoxy composite containing barely visible impact damage (BVID). The study investigates the effect of increasing volume content of z-pins (up to 4%) on the barely visible impact damage resistance, post-impact compression fatigue properties, and fatigue damage mechanisms of a quasi-isotropic Carbon-Epoxy material. The study reveals new insights into the impact damage resistance of z-pinned composites. Z-pins induce different responses in the compression fatigue properties of the quasi-isotropic composite following low or high-energy impact loading. Z-pins proved ineffective at increasing the fatigue properties when the quasi-isotropic composite contained low-energy BVID. However, z-pins were effective at improving the fatigue performance of the composite with high-energy BVID, with the post-impact fatigue life and fatigue endurance limit increasing with the pin content. The improvement in fatigue performance is due solely to the increased resistance against high-energy impact damage imposed by the z-pins. It is also found that z-pins do not affect the fatigue mechanism or fatigue damage growth rate of the composite containing BVID.
K Yano - One of the best experts on this subject based on the ideXlab platform.
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probabilistic anisomorphic constant fatigue life diagram approach for prediction of p s n curves for woven carbon epoxy Laminates at any stress ratio
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Masamichi Kawai, K YanoAbstract:Abstract A general engineering methodology to construct a family of anisomorphic constant fatigue life (CFL) diagrams with probability of failure as the parameter that allows efficiently predicting P–S–N curves at any stress ratios is developed and validated for a plain weave fabric carbon/epoxy Laminate. Constant amplitude fatigue tests are first performed to obtain statistical samples of fatigue life at different stress levels and stress ratios, respectively. Static tensile and compressive strength data are also collected. The Kolmogorov–Smirnov and Anderson–Darling goodness-of-fit tests suggest that both two-parameter lognormal and Weibull distributions are acceptable as the distributions for the static strength and fatigue life data, respectively, at the significance level of 5%. Then, we attempt to develop a methodology for efficient construction of the anisomorphic CFL diagrams for different constant values of probability of failure. It requires the P–S–N curves for any percentile points of the distribution for the critical stress ratio. To come up with this requirement, a probabilistic scaling law is formulated. It takes account of the probability-of-failure dependence of the critical stress ratio and the stress-ratio dependence of the P–S–N curve for the critical stress ratio. Finally, the anisomorphic CFL diagrams for different constant values of probability of failure are predicted using the proposed methodology, and they are shown to be in good agreement with the experimental results. It is also demonstrated that the P–S–N curves can efficiently and accurately be predicted for the woven CFRP Laminate at any stress ratios using the proposed probabilistic anisomorphic CFL diagram approach.
Dimitrios Zarouchas - One of the best experts on this subject based on the ideXlab platform.
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Adapted anisomorphic model for fatigue life prediction of CFRP Laminates under constant amplitude loading
International Journal of Fatigue, 2019Co-Authors: A.a.r. Broer, Dimitrios ZarouchasAbstract:Abstract A new constant life diagram (CLD) model is proposed to predict the fatigue life of carbon fibre-reinforced epoxy Laminates under constant amplitude (CA) loading. The CLD is asymmetric and non-linear, and it is built upon the anisomorphic CLD model. It consists of two sub-models; one sub-model is applicable to Laminates with lay-ups characterised by a larger ultimate tensile strength (UTS) than absolute ultimate compressive strength (UCS): UTS ⩾ ∣UCS∣, while the second sub-model can be applied to those exhibiting the opposite tendency: ∣UCS∣ > UTS. Combined, the sub-models can predict the fatigue life of any Carbon-Epoxy Laminate. The CLD can be constructed using only static strength data and fatigue life data related to one stress ratio (R), defined as either R = 0.1 or R = - 1.0 . An experimental campaign was conducted on a Carbon-Epoxy Laminate with a lay-up of [90/0/90]2S to validate the first CLD sub-model. Additionally, a second case study from literature with a lay-up of [45/90/-45/0]2S was employed for validation. The second CLD sub-model was evaluated using two coupon case studies from literature with lay-ups of [±60]3S and [45]16. The predicted and experimentally obtained fatigue lives showed agreements for different R-ratios, and the observed prediction errors were in ranges similar to those of the original anisomorphic CLD model. Hence, the presented CLD model allows for fatigue life predictions in scales similar to experimental results while reducing the required experimental efforts with respect to the anisomorphic CLD model.
T Teranuma - One of the best experts on this subject based on the ideXlab platform.
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a multiaxial fatigue failure criterion based on the principal constant life diagrams for unidirectional carbon epoxy Laminates
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: Masamichi Kawai, T TeranumaAbstract:Abstract A new fatigue failure criterion for unidirectional composites has been developed on the basis of the modified Tsai-Hill static failure criterion that can distinguish between the static strengths in tension and compression. A new idea is to calculate the principal fatigue strengths involved by the fatigue failure criterion using the associated constant fatigue life (CFL) diagrams. First, the in-plane principal CFL diagrams for a unidirectional carbon/epoxy Laminate in longitudinal, transverse and in-plane shear loading conditions are identified by experiment. Then, the four-segment anisomorphic CFL diagram approach, which was developed in an earlier study, is shown to be applicable in accurate description of all of the principal CFL diagrams that are highly nonlinear and asymmetric in shape. Finally, it is demonstrated that the off-axis S–N relationship for the unidirectional carbon/epoxy Laminate can accurately and efficiently be predicted for any stress ratio and any fiber orientation using the proposed fatigue life prediction methodology.