The Experts below are selected from a list of 10113 Experts worldwide ranked by ideXlab platform
T A Hafiz - One of the best experts on this subject based on the ideXlab platform.
-
life prediction of carbon fiber reinforced polymers using time Temperature Shift Factor
International Journal of Engineering, 2020Co-Authors: T A HafizAbstract:The properties of Carbon Fiber–Reinforced Polymers (CFRP) are greatly affected under extreme environmental conditions. This paper reports an experimental study to determine the response of IM7-carbon/977-2 cycom epoxy laminates under different humidity and temprature conditions. Short-term 3-point bending creep tests using Dynamic Mechanical Analysis (DMA) were used to test the dry and saturated samples at various Temperature levels. The dry coupons were tested at the room Temperature (RT) and at 60-120 °C with 20 °C increment and then at 130 °C, 150-180 °C with 10 °C increment for each next test. The saturated (wet) coupons were tested at RT, 40 - 120 °C with 10 °C increment in Temperature for each next test and at 145 °C, 150 °C, and 160 °C. The time-Temperature Shift Factor (TTSF) was applied and it is shown that the viscoelastic behavior of the invetigated IM7-carbon/977-2 epoxy laminates, is accurately predicted through the use of TTSF. It has also been shown that determining the viscoelastic behavior at elevated Temperatures helps to predict Temperature below the glass transition Temperature using TTSF. The long-term life of the material is relatively easily predicted using TTSF by conducting traditional short-term laboratory tests.
Witold Brostow - One of the best experts on this subject based on the ideXlab platform.
-
time stress correspondence in viscoelastic materials an equation for the stress and Temperature Shift Factor
Materials Research Innovations, 2000Co-Authors: Witold BrostowAbstract:Stress-time correspondence principle discovered experimentally by O'Shaughnessy already in 1948 [1] is considered. Using the Doolittle formula for the viscosity as a function of free volume [2], an...
-
creep and stress relaxation in a longitudinal polymer liquid crystal prediction of the Temperature Shift Factor
Journal of Chemical Physics, 1999Co-Authors: Witold Brostow, Nandika Anne Dsouza, J Kubat, R D MaksimovAbstract:The polymer liquid crystal PLC is the PET/0.6PHB copolymer; PET=poly(ethylene terephthalate), PHB=ρ-hydroxybenzoic acid (LC): 0.6=the mole fraction of PHB. This is a multiphase system with PHB-rich islands in a PET-rich matrix. Tensile creep compliance was measured isothermally from 20 °C to 160 °C in 10 °C intervals. Master curves were determined using the time–Temperature superposition for 20 °C and for the glass transition Temperature of the PET-rich phase TgPET=62 °C. Experimental values of the Temperature Shift Factor aT as a function of Temperature T agree in the entire T range with those from Eq. (7) relating aT to the reduced volume ṽ and the Hartmann equation of state Eq. (10). Values of aT(T) calculated from the Williams–Landel–Ferry (WLF) formula give very large errors below Tg. A control 14 months creep experiment agrees with the theoretical predictions from Eq. (7). Stress relaxation experiments were performed under the constant strain of 0.5% from 20 °C to 120 °C, again master curves were de...
R D Maksimov - One of the best experts on this subject based on the ideXlab platform.
-
creep and stress relaxation in a longitudinal polymer liquid crystal prediction of the Temperature Shift Factor
Journal of Chemical Physics, 1999Co-Authors: Witold Brostow, Nandika Anne Dsouza, J Kubat, R D MaksimovAbstract:The polymer liquid crystal PLC is the PET/0.6PHB copolymer; PET=poly(ethylene terephthalate), PHB=ρ-hydroxybenzoic acid (LC): 0.6=the mole fraction of PHB. This is a multiphase system with PHB-rich islands in a PET-rich matrix. Tensile creep compliance was measured isothermally from 20 °C to 160 °C in 10 °C intervals. Master curves were determined using the time–Temperature superposition for 20 °C and for the glass transition Temperature of the PET-rich phase TgPET=62 °C. Experimental values of the Temperature Shift Factor aT as a function of Temperature T agree in the entire T range with those from Eq. (7) relating aT to the reduced volume ṽ and the Hartmann equation of state Eq. (10). Values of aT(T) calculated from the Williams–Landel–Ferry (WLF) formula give very large errors below Tg. A control 14 months creep experiment agrees with the theoretical predictions from Eq. (7). Stress relaxation experiments were performed under the constant strain of 0.5% from 20 °C to 120 °C, again master curves were de...
Thomas S Gates - One of the best experts on this subject based on the ideXlab platform.
-
effects of physical aging on long term creep of polymers and polymer matrix composites
International Journal of Solids and Structures, 1995Co-Authors: Catherine L Brinson, Thomas S GatesAbstract:Abstract For many polymeric materials in use below the glass transition Temperature, the long term viscoelastic behavior is greatly affected by physical aging. To use polymer matrix composites as critical structural components in existing and novel technological applications, this long term behavior of the material system must be understood. Towards that end, this study applied the concepts governing the mechanics of physical aging in a consistent manner to the study of laminated composite systems. Even in fiber dominated lay-ups, the effects of physical aging are found to be important in the long term behavior of the composite. This paper first lays out, in a self-consistent manner, the basic concepts describing physical aging of polymers. Several aspects of physical aging which have not been previously documented are also explored in this study, namely the effects of aging into effective equilibrium and a relationship to the time-Temperature Shift Factor. The physical aging theory is then extended to develop the long term compliance/modulus of a single lamina with varying fiber orientation. The latter is then built into classical lamination theory to predict long time response of general laminated composites. Comparison to experimental data is excellent. In the investigation of fiber oriented lamina and laminates, it is illustrated that the long term response can be counter-intuitive, stressing the need for consistent modeling efforts to make long term predictions of laminates to be used in structural situations.
Yanqing Zhao - One of the best experts on this subject based on the ideXlab platform.
-
extension of modified havriliak negami model to characterize linear viscoelastic properties of asphalt binders
Journal of Materials in Civil Engineering, 2016Co-Authors: Yanqing Zhao, Peisong Chen, Dandan CaoAbstract:AbstractAccurate characterization of mechanical properties of asphalt binders plays an important role in the evaluation and selection of binders, and in the design and analysis of mixtures. In this study the modified Havriliak-Negami model previously proposed for complex modulus of asphalt concrete is extended to account for the steady-state flow behavior of viscoelastic liquid materials. The analytical forms of storage and loss modulus master curves are derived from the complex modulus model through complex algebra. The Kronig-Kramers relations of the model are satisfied so that various LVE functions are equivalent and the causality of the model is fulfilled. In addition, the same time-Temperature Shift Factor applies to various LVE functions. Thus, the model is consistent with the LVE theory. The model is fitted to complex modulus test results of various asphalt binders. The results show that the model can accurately characterize the properties of asphalt binders, regardless of whether they show viscoel...
-
time Temperature superposition for asphalt mixtures with growing damage and permanent deformation in compression
Transportation Research Record, 2003Co-Authors: Yanqing ZhaoAbstract:The objective in this study was to check the validity of the time-Temperature superposition principle for hot-mix asphalt (HMA) with growing damage and viscoplastic strain in the compression state, which is essential for the permanent deformation characterization of HMA. Constant crosshead rate compression tests were conducted at Temperatures between 25° and 55°, and data were analyzed to construct the stresslog reduced-time master curves for various strain levels. Research results indicate that HMA with growing damage remains thermorheologically simple in the Temperature range used in this study and that the time-Temperature Shift Factor is only a function of Temperature and is independent of the strain level. Two types of tests, the repeated creep and recovery test and the cyclic sinusoidal loading test, were performed in this study to validate the time-Temperature superposition in loading histories commonly used in asphalt mixture testing. The results further confirm that the time-Temperature superposi...
