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Masamichi Kawai - One of the best experts on this subject based on the ideXlab platform.
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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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temperature dependence of off axis tensile creep rupture behavior of a unidirectional carbon Epoxy Laminate
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Masamichi Kawai, Takahiko SagawaAbstract: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.
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off axis tensile creep rupture behavior of a unidirectional cfrp Laminate at high temperatures
Transactions of the Japan Society of Mechanical Engineers. A, 2008Co-Authors: Masamichi Kawai, Takahiko SagawaAbstract: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.
Takahiko Sagawa - One of the best experts on this subject based on the ideXlab platform.
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temperature dependence of off axis tensile creep rupture behavior of a unidirectional carbon Epoxy Laminate
Composites Part A-applied Science and Manufacturing, 2008Co-Authors: Masamichi Kawai, Takahiko SagawaAbstract: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.
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off axis tensile creep rupture behavior of a unidirectional cfrp Laminate at high temperatures
Transactions of the Japan Society of Mechanical Engineers. A, 2008Co-Authors: Masamichi Kawai, Takahiko SagawaAbstract: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.
Shaik Jeelani - One of the best experts on this subject based on the ideXlab platform.
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dynamic punch shear characterization of plain weave graphite Epoxy composites at room and elevated temperatures
Composite Structures, 2005Co-Authors: M V Hosur, S Waliul M Islam, Piyush K Dutta, U K Vaidya, Ashok Kumar, Shaik JeelaniAbstract:Abstract In many situations, composite structures are subjected to dynamic loading. To design such structures, there is a need of dynamic material properties. In the current investigation, a compression Split Hopkinson Pressure Bar was modified to load the samples in punch shear mode. Experimental studies were conducted to characterize 24 layer plain weave graphite/Epoxy Laminate samples. Laminates were manufactured using vacuum assisted resin infusion molding process. Samples of nominal size 26 mm × 13 mm × 4 mm were subjected to dynamic punch shear test at three different pressure settings that yielded strain rates in the range of 1415–3601/s at room and elevated temperatures of 51.7 °C, 79.4 °C and 107.2 °C. Dynamic shear stress–strain properties were evaluated. Failure modes were characterized through optical and scanning electron microscopy. Results of the tests indicate that the dynamic shear strength increases with increase in the strain rate and decreases with temperature for a given strain rate. Higher temperature causes the softening of matrix.
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experimental studies on the punch shear characterization of satin weave graphite Epoxy composites at room and elevated temperatures
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2004Co-Authors: M V Hosu, Uday K Vaidya, S Waliul M Islam, Piyush K Dutta, Shaik JeelaniAbstract:Abstract In many situations, composite structures are subjected to dynamic loading. To design such structures, there is a need of dynamic material properties. In the current investigation, a compression split Hopkinson pressure bar (SHPB) was modified to load the samples in punch shear mode. Experimental studies were conducted to characterize 24-layer satin weave graphite/Epoxy Laminate samples. Laminates were manufactured using vacuum assisted resin infusion molding (VARIM) process. Samples of nominal size 26 mm ×13 mm ×4 mm were subjected to dynamic punch shear test at three different pressure settings that yielded strain rates in the range of 1500–3500 s−1 at room and elevated temperatures of 51.7, 79.4 and 107.2 °C. Dynamic shear stress–strain properties were evaluated. Failure modes were characterized through optical and scanning electron microscopy. Results of the tests indicate that the dynamic shear strength increases with increase with the strain rate and decreases with temperature for a given strain rate. Higher temperature causes the softening of matrix.
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high strain rate compression response of carbon Epoxy Laminate composites
Composite Structures, 2001Co-Authors: M V Hosur, J Alexander, U K Vaidya, Shaik JeelaniAbstract:Abstract Composite materials exhibit excellent mechanical properties over metallic materials and hence are increasingly considered for high technology applications. In many practical situations, the structures are subjected to loading at very high strain rates. Material and structural response vary significantly under such loading as compared to static loading. A structure that is expected to perform under dynamic loading conditions, if designed with the static properties, might be too conservative. Hence, it is necessary to characterize the advanced composites under high strain rate loading. In the current investigations, the response of carbon/Epoxy Laminated composites under high strain rate compression loading is considered using a modified split Hopkinson Pressure Bar (SHPB) setup at three different strain rates of 82, 164 and 817 s −1 . The Laminates were fabricated using 32 plies of a DA 4518 unidirectional carbon/Epoxy prepreg system. Both unidirectional and cross-ply Laminates were considered for the study. In the case of cross-ply Laminates, the samples were tested in the thickness as well as in the in-plane direction. The unidirectional Laminate samples were subjected to loading along 0° and 90° directions. Dynamic stress–strain plot was obtained for each sample and compared with the static compression test result. The results of the study indicate that the dynamic strength (with the exception of through the thickness loading of cross-ply Laminates) and stiffness exhibit considerable increase as compared to the static values within the tested range of strain rates.
Adrian P. Mouritz - One of the best experts on this subject based on the ideXlab platform.
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environmental durability of z pinned carbon fibre Epoxy Laminate exposed to water
Composites Science and Technology, 2012Co-Authors: Adrian P. MouritzAbstract:Abstract The influence of z-pins on the water absorption properties of a quasi-isotropic carbon fibre–Epoxy Laminate is assessed. Fibrous composite pins accelerate the moisture absorption rate and increase the total absorbed moisture concentration when the Laminate is immersed in water. However, the moisture absorption properties of the Laminate are not affected significantly by pins when exposed to hot and humid air. Water diffusion into the z-pinned Laminate is aided by interfacial cracks between the pins and Laminate. Also, the axial alignment of fibres within the composite pins in the through-thickness direction increases the water absorption rate. Pin pull-out tests reveal that water absorption reduces the mode I crack bridging traction load generated by pins by reducing the shear strength of the pin-Laminate interface. This indicates that the mode I delamination toughness induced by pinning is weakened by moisture absorption.
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self healing of delamination cracks in mendable Epoxy matrix Laminates using poly ethylene co methacrylic acid thermoplastic
Composites Part A-applied Science and Manufacturing, 2012Co-Authors: Khomkrit Pingkarawat, Russell J Varley, C H Wang, Adrian P. MouritzAbstract:Abstract This paper investigates the self-healing repair of delamination cracks in a carbon fibre–Epoxy Laminate using the mendable thermoplastic poly[ethylene- co -(methacrylic acid)] (EMAA). The effects of different types (fibres or particles) and concentrations of the mendable EMAA agent on the self-healing efficiency was measured using mode I interlaminar fracture toughness testing and fractographic analysis. The EMAA was effective in healing delamination damage and increasing the fracture toughness compared to the original Laminate. High healing efficiency was achieved by the wide area flow of EMAA (increase of ∼25 times) through delamination cracks under the pressure delivery mechanism. High recovery in the fracture toughness was achieved after healing by the formation of large-scale EMAA-bridging ligaments along the delamination, which is a toughening mechanism unique to this type of self-healing material. EMAA proved effective for the multiple repairs of delamination cracks with some loss in the self-healing efficiency of the mendable Laminates.
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toughening and self healing of Epoxy matrix Laminates using mendable polymer stitching
Composites Science and Technology, 2012Co-Authors: Sailing He, T Yang, Jin Zhang, C H Wang, Adrian P. MouritzAbstract:Abstract This paper presents an experimental study into a new type of stitched fibre–polymer Laminate that combines high interlaminar toughness with self-healing repair of delamination damage. Poly(ethylene-co-methacrylic acid) (EMAA) filaments were stitched into carbon fibre/Epoxy Laminate to create a three-dimensional self-healing fibre system that also provides high fracture toughness. Double cantilever beam testing revealed that the stitched EMAA fibres increased the mode I interlaminar fracture toughness (by ∼120%) of the Laminate, and this reduced the amount of delamination damage that must subsequently be repaired by the self-healing stitches. The 3D stitched network was effective in delivering self-healing EMAA material extracted from the stitches into the damaged region, and this resulted in high recovery in the delamination fracture toughness (∼150% compared to the original material). The new self-healing stitching method provides high toughness which resists delamination growth while also having the functionality to repeatedly repair multiple layers of damage in Epoxy matrix Laminates.
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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.
T L Hsu - One of the best experts on this subject based on the ideXlab platform.
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electromechanical fatigue behavior of graphite Epoxy Laminate embedded with piezoelectric actuator
Smart Materials and Structures, 2000Co-Authors: S Mall, T L HsuAbstract:Fatigue behavior of graphite/Epoxy Laminate, having [0/±45/90]S lay-up and embedded with piezoelectric (lead zirconate-titanate, PZT) actuator, was investigated under combined mechanical and electrical cycling loading condition, and in only mechanical fatigue condition. The PZT was inserted into a cutout area in the two middle 90° plies. Experiments involved cycling of specimens at different maximum stress levels along with the excitation of the embedded actuator from -10 V to -100 V or 10 V to 100 V, which resulted in either in-phase or out-of-phase electrically induced strain relative to the applied mechanical loading or strain. In general, embedded PZT performed better in the out-of-phase than in the in-phase electromechanical fatigue condition. The fatigue life of the embedded PZT was more than one million cycles, for the applied maximum stress level well above its design limit in the out-of phase electromechanical and in only mechanical fatigue conditions. The embedded PZT failed before one million cycles during the in-phase test at the applied maximum stress equal to its design limit. Above this stress level, a sharp reduction in the fatigue life occurred during the in-phase electromechanical cycling condition.
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electromechanical fatigue behavior of graphite Epoxy Laminate embedded with piezoelectric actuator
Smart Structures and Materials 1999: Smart Structures and Integrated Systems, 1999Co-Authors: S Mall, T L HsuAbstract:Fatigue behavior of graphite/Epoxy Laminate, having [0/+/- 45/90]s lay-up and embedded with piezoelectric (lead zirconate-titanate, PZT) actuator, was investigated under combined mechanical and electrical cycling loading condition. The PZT was inserted into a cutout area in the two middle 90-degrees plies. Experiments involved cycling of specimens at various maximum stress levels along with the excitation of the embedded actuator from -10 V to -100 V or 10 V to 100 V, which resulted in either in-phase or out-of-phase electrically induced strain relative to the applied mechanical loading or strain. In general, PZT performed better in the out-of phase than in the in-phase electromechanical fatigue condition. The fatigue life of the embedded PZT was more than one million cycles, for the applied maximum stress levels well above its design limit in the out-of-phase electromechanical and in only mechanical fatigue conditions. The PZT failed before one million cycles during the in-phase test at the applied maximum stress equal to its design limit. Above this stress level, a sharp drop-off occurred in the fatigue life during the in-phase electromechanical cycling condition.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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electromechanical fatigue behavior of graphite Epoxy Laminate embedded with piezoelectric actuator
Proceedings of SPIE the International Society for Optical Engineering, 1999Co-Authors: S Mall, T L HsuAbstract:Fatigue behavior of graphite/Epoxy Laminate, having [0/′45/90] s lay-up and embedded with piezoelectric (lead zirconate-titanate, PZT) actuator, was investigated under combined mechanical and electrical cycling loading condition. The PZT was inserted into a cutout area in the two middle 90-degrees plies. Experiments involved cycling of specimens at various maximum stress levels along with the excitation of the embedded actuator from -10 V to -100 V or 10 V to 100 V, which resulted in either in-phase or out-of-phase electrically induced strain relative to the applied mechanical loading or strain. In general, PZT performed better in the out-of phase than in the in-phase electromechanical fatigue condition. The fatigue life of the embedded PZT was more than one million cycles, for the applied maximum stress levels well above its design limit in the out-of phase electromechanical and in only mechanical fatigue conditions. The PZT failed before one million cycles during the in-phase test at the applied maximum stress equal to its design limit. Above this stress level, a sharp drop-off occurred in the fatigue life during the in-phase electromechanical cycling condition.
