The Experts below are selected from a list of 315 Experts worldwide ranked by ideXlab platform
Dai Gil Lee - One of the best experts on this subject based on the ideXlab platform.
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effect of the smart Cure Cycle on the performance of the co Cured aluminum composite hybrid shaft
Composite Structures, 2006Co-Authors: Sang Wook Park, Hui Yun Hwang, Dai Gil LeeAbstract:Abstract In this work, a smart curing method for the co-Cured aluminum/composite hybrid shaft which can reduce the thermal residual stresses generated during co-curing bonding operation between the composite layer and the aluminum tube was applied. In order to reduce the thermal residual stresses generated during co-Cure bonding stages due to the difference of coefficients of thermal expansions (CTE) of the composite and the aluminum tube, a smart Cure Cycle composed of cooling and reheating Cycles was applied. The heating and cooling operations were realized using a pan type heater and water cooling system. The thermo-mechanical properties of the high modulus carbon epoxy composite were measured by a DSC (differential scanning calorimetry) and rheometer to obtain an optimal time to apply the cooling operation. Curvature experiment of the co-Cure bonded steel/composite strip was performed to investigate the effect of Cure Cycle on generation of the thermal residual stress. Also, the thermal residual stresses of the aluminum/composite hybrid shaft were measured using strain gauges with respect to Cure Cycles. Finally, torsional fatigue test and vibration test of the aluminum/composite hybrid shaft were performed, and it has been found that this method might be used effectively in manufacturing of the co-Cured aluminum/composite hybrid propeller shaft to improve the dynamic torque characteristics.
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reduction of residual stresses in thick walled composite cylinders by smart Cure Cycle with cooling and reheating
Composite Structures, 2006Co-Authors: Jong Woon Kim, Dai Gil Lee, Jihyung Lee, Hyoung Geun KimAbstract:Abstract The nozzle parts of solid rocket motors must endure both the internal pressure generated by high temperature exhaust gas and the mechanical load generated by steering operation. Therefore, the nozzle parts of solid rocket motors are fabricated with thick carbon fiber phenolic resin composites. When the thick-walled phenolic composite cylinder is cooled down from the curing temperature of about 155 °C to the room temperature, thermal residual stresses are created due to the anisotropic thermal deformation of the composite structure. In this paper, a smart Cure method with cooling and reheating was developed to reduce residual stresses in thick-wound composite cylinders made of carbon phenolic woven composite. The optimal Cure Cycle was obtained to reduce the residual stresses without increasing processing time and applied to fabrication of the thick-walled composite cylinder. From the residual stresses measured by the radial-cut-cylinder-bending method, it was found that the residual stresses were reduced 30% by using the smart Cure method.
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Cure Cycle for thick glass epoxy composite laminates
Journal of Composite Materials, 2002Co-Authors: Dai Gil LeeAbstract:Duringthe curingprocess of thick glass/epoxy composite laminates, substantial amounts of temperature lagand overshoot at the center of the laminates is usually experienced due to the large thickness and low thermal conductivity of the glass/epoxy composites, which require a long time for full and uniform consolidation. In this work, the temperature profiles of a 20mm thick unidirectional glass/epoxy laminate duringan autoclave vacuum bag process were measured and compared with the numerically calculated results. For the calculation of distributions of the temperature, degree of Cure, resin pressure, exothermic heat and required time for full consolidation by three-dimensional finite element analyses, the effects of convective heat transfer coefficient and geometry of mold and bagging assembly on the temperature profiles were taken into consideration. Based on the numerical results, an optimized Cure Cycle with the coolingand reheatingsteps was developed by minimizingthe objective function to reduce the te...
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development of an autoclave Cure Cycle with cooling and reheating steps for thick thermoset composite laminates
Journal of Composite Materials, 1997Co-Authors: Jinsoo Kim, Dai Gil LeeAbstract:In this study, an autoclave Cure Cycle for thick thermosetting resin matrix composite materials was developed to reduce the temperature overshoot. To predict the temperature distribution of thick thermosetting composite laminates during Cure, the heat transfer equation, including the heat generation term, was simulated by the finite difference method (FDM). Using the simulated results, the Cure Cycle was obtained by modifying the conventional Cure Cycle. The steps of cooling and reheating, which were determined by the Cure rate and temperature at the midpoint of the laminate, were introduced into the conventional Cure Cycle. The developed Cure Cycle was used to Cure 15 and 30 mm (100 and 200 ply) thick laminates and was found to be effective for the reduction of temperature over-shoot
Sang Wook Park - One of the best experts on this subject based on the ideXlab platform.
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smart Cure Cycle with cooling and reheating for co Cure bonded steel carbon epoxy composite hybrid structures for reducing thermal residual stress
Composites Part A-applied Science and Manufacturing, 2006Co-Authors: Sang Wook ParkAbstract:Abstract In this work, a smart Cure Cycle with cooling and reheating for co-Cure bonded steel/carbon epoxy composite hybrid structures was developed to reduce the fabricational thermal residual stress between the steel and carbon epoxy composite material. The thermo-mechanical properties of the high modulus carbon epoxy composite were measured by a Differential scanning calorimetry (DSC) and rheometer to obtain the optimal time to apply the cooling operation. The static lap shear strength of the co-Cure bonded steel/composite lap joints and tensile strength of the composite specimen were measured to investigate the effect of Cure Cycle on the thermal residual stress. Also, the deflection of the hybrid structures was measured to measure the actual Cure temperature with respect to various Cure Cycles. From the experiments, it was found that the smart Cure Cycle with cooling and reheating not only reduced the fabricational thermal residual stress but also improved the strength and dimensional accuracy of the hybrid structures.
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effect of the smart Cure Cycle on the performance of the co Cured aluminum composite hybrid shaft
Composite Structures, 2006Co-Authors: Sang Wook Park, Hui Yun Hwang, Dai Gil LeeAbstract:Abstract In this work, a smart curing method for the co-Cured aluminum/composite hybrid shaft which can reduce the thermal residual stresses generated during co-curing bonding operation between the composite layer and the aluminum tube was applied. In order to reduce the thermal residual stresses generated during co-Cure bonding stages due to the difference of coefficients of thermal expansions (CTE) of the composite and the aluminum tube, a smart Cure Cycle composed of cooling and reheating Cycles was applied. The heating and cooling operations were realized using a pan type heater and water cooling system. The thermo-mechanical properties of the high modulus carbon epoxy composite were measured by a DSC (differential scanning calorimetry) and rheometer to obtain an optimal time to apply the cooling operation. Curvature experiment of the co-Cure bonded steel/composite strip was performed to investigate the effect of Cure Cycle on generation of the thermal residual stress. Also, the thermal residual stresses of the aluminum/composite hybrid shaft were measured using strain gauges with respect to Cure Cycles. Finally, torsional fatigue test and vibration test of the aluminum/composite hybrid shaft were performed, and it has been found that this method might be used effectively in manufacturing of the co-Cured aluminum/composite hybrid propeller shaft to improve the dynamic torque characteristics.
Baotong Huang - One of the best experts on this subject based on the ideXlab platform.
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Cure processing modeling and Cure Cycle simulation of epoxy terminated poly phenylene ether ketone v estimation of temperature distribution during Cure process
Polymer Engineering and Science, 1998Co-Authors: Qiang Wang, Ping Xia, Tianlu Chen, Baotong HuangAbstract:A numerical method to estimate temperature distribution during the Cure of epoxy-terminated poly(phenylene ether ketone) (E-PEK)-based composite is suggested. The effect of the temperature distribution on the selection of Cure Cycle is evaluated using a suggested alternation criterion. The effect of varying heating rate and thickness on the temperature distribution, viscosity distribution and distribution of the extent of Cure reaction are discussed based on the combination of the here-established temperature distribution model and the previously established curing kinetics model and chemorheological model. It is found that, for a thin composite (<=10mm) and low heating rate (<=2.5K/min), the effect of temperature distribution on Cure Cycle and on the processing window for pressure application can be neglected. Low heating rate is of benefit to reduce the temperature gradient. The processing window for pressure application becomes narrower with increasing thicknesses of composite sheets. The validity of the temperature distribution model and the modified processing window is evaluated through the characterization of mechanical and physical properties of E-PEK-based composite fabricated according to different temperature distribution conditions.
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Cure processing modeling and Cure Cycle simulation of epoxy terminated poly phenylene ether ketone iv Cure Cycle simulation
Journal of Applied Polymer Science, 1997Co-Authors: Qiang Wang, Ping Xia, Tianlu Chen, Baotong HuangAbstract:Epoxy-terminated poly(phenylene ether ketone) (E-PEK) developed in this Institute is a candidate matrix resin for polymer composites as structural materials. Cure Cycles for this reaction system were simulated according to the previously established processing model. It is found that for the E-PEK system, the curing process is best completed by a stepwise Cure Cycle comprising two isothermal processes at different temperatures, T-1 and T-2. The Cure Cycles over a wide range of processing parameters simulated, based on the established processing model, indicate that the processing window is width-adjustable. Analysis of the mechanical properties of the composite sheets showed that the simulated Cure Cycles are acceptable and reliable. (C) 1997 John Wiley & Sons, Inc.
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Cure processing modeling and Cure Cycle simulation of epoxy terminated poly phenylene ether ketone iii determination of the time of pressure application
Journal of Applied Polymer Science, 1997Co-Authors: Qiang Wang, Ping Xia, Tianlu Chen, Baotong HuangAbstract:The curing temperature, pressure, and curing time have significant influence on finished thermosetting composite products. The time of pressure application is one of the most important processing parameters in the manufacture of a thermosetting composite. The determination of the time of pressure application relies on analysis of the viscosity variation of the polymer, associated with curing temperature and curing time. To determine it, the influence of the time of pressure application on the physical properties of epoxy-terminated poly(phenylene ether ketone) (E-PEK)-based continuous carbon fiber composite was studied. It was found that a stepwise temperature Cure Cycle is more suitable for manufacture of this composite. There are two viscosity valleys, in the case of the E-PEK system, associated with temperature during a stepwise Cure Cycle. The analysis on the effects of reinforcement fraction and defect content on the composite sheet quality indicates that the width-adjustable second viscosity valley provides a suitable pressing window. The viscosity, ranging from 400 to 1200 Pa . s at the second viscosity valley, is the optimal viscosity range for applying pressure to ensure appropriate resin flow during curing process, which enables one to get a finished composite with optimal fiber volume fraction and low void content. (C) 1997 John Wiley & Sons, Inc.
Byron R Pipes - One of the best experts on this subject based on the ideXlab platform.
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Cure history dependence of residual deformation in a thermosetting laminate
Composites Part A-applied Science and Manufacturing, 2017Co-Authors: Oleksandr G. Kravchenko, Sergii G. Kravchenko, Byron R PipesAbstract:Abstract The Cure history dependent residual deformation in a thermosetting composite laminate was investigated using bi-lamina strip sample with [0/904] stacking-sequence. The samples were subjected to Cure Cycles with different heating profiles. Significant dependence of the residual strip deflection was found to relate to (i) the interaction of thermal expansion and Cure shrinkage of resin and (ii) dependence of resin modulus development on Cure strain rate. The lamina constitutive model was proposed to include Cure induced shrinkage and composite hardening during Cure. The model was calibrated following the single and multiple ramps Cure Cycles and applied to a number of two hold stage Cure Cycles with constant maximum temperature. The heating ramp of the Cure Cycle was varied allowing decreasing the residual deformation at ambient conditions after Cure. The presented methodology can be applied for designing the Cure Cycle to reduce the amount of residual deformation in composite materials from manufacturing.
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chemical and thermal shrinkage in thermosetting prepreg
Composites Part A-applied Science and Manufacturing, 2016Co-Authors: Oleksandr G. Kravchenko, Sergii G. Kravchenko, Byron R PipesAbstract:Abstract A methodology for predicting residual Cure deformation and stresses in composite laminates during Cure is proposed. The technique employs an unbalanced cross-ply strip denoted as a “bi-lamina” strip to measure the in situ development of chemical and thermal shrinkage deformation during a specified thermal Cycle. The constitutive model of the composite material was developed based on self-consistent micro-mechanical homogenization with variable resin thermo-mechanical material properties during the Cure Cycle. The resin properties were determined as a function of Cure and temperature using different experimental techniques, including differential scanning calorimetry, digital image correlation, rheometry and dynamic mechanical analysis. The predicted bending deflection profiles of the strip agreed closely with experimental observations. The proposed methodology can be used to validate the material model of the resin and composite during the Cure Cycle.
Lee Dai Gil - One of the best experts on this subject based on the ideXlab platform.
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smart Cure Cycle for reducing the thermal residual stress of a co Cured e glass carbon epoxy composite structure for a vanadium redox flow battery
Composite Structures, 2015Co-Authors: Nam Soohyun, Lee Dongyoung, Choi Ilbeom, Lee Dai GilAbstract:Abstract The vanadium redox flow battery (VRFB) is considered as one of the most promising energy storage system in the future. It is composed of two endplates and a stack which consists of flow frame (FF), electrode, bipolar plate (BP) and membrane. Because the electrolytes flowing in the stack are sulfuric-acid-based solutions, prevention of leakage is important. The unified structure of the FF and the BP manufactured by co-curing E-glass/epoxy and carbon/epoxy composites not only prevents leakage, but also simplifies assembling process. However, large thermal residual stress is induced due to the difference of coefficients of thermal expansion between E-glass/epoxy and carbon/epoxy composites. In this work, smart Cure Cycle was developed to reduce the thermal residual stress of the co-Cured E-glass/carbon/epoxy structure for VRFB. The deformations of structure fabricated using smart Cure Cycle were investigated with respect to the degree of Cure and post-Cure process using the viscoelastic properties of composite materials during post-Cure process. In addition, the thermal residual stress and actual bonding temperature were calculated. Using the experimental results of degree of Cure and actual bonding temperature, a finite element analysis was performed to verify the stress of the co-Cured FF–BP structure as a function of the Cure Cycles.
