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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
The Korean Society for Composite Materials
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Volume & Issues
Volume 12, Issue 6 - Dec 1999
Volume 12, Issue 5 - Oct 1999
Volume 12, Issue 4 - Aug 1999
Volume 12, Issue 3 - Jun 1999
Volume 12, Issue 2 - Apr 1999
Volume 12, Issue 1 - Feb 1999
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Characterization of Thermal Expansion Coefficients of Carbon/Epoxy Composite for Temperature Variation
Composites Research, volume 12, issue 6, 1999, Pages 1~7
The change of the coefficients of thermal expansion(CTE) of Carbon/Epoxy was investigated for the temperature variation and a prediction model for the change of CTE was proposed. Elastic properties and CTEs in the principal material directions were measured in the range of room temperature to cure temperature and characterized as functions of temperature. By applying the characterized properties to the classical lamination theory, a computational method to predict the change of CTEs of a general laminate for temperature variation was proposed. the coefficients of thermal expansion of laminates with various stacking sequences were measured and compared with those predicted. Good agreements between the predicted results and the experimental data show that the c hanges of CTEs of a general laminate for temperature variation can be predicted well by using the proposed method.
A Study on the Impact Properties of Solid-phase Formed Glass Fiber Reinforced Thermoplastic Composite
Composites Research, volume 12, issue 6, 1999, Pages 8~14
This research is focused on the investigation of impact strength and the microscopic observation of material behavior of glass fiber reinforced polypropylene in solid phase forming. The fiber weight per-centage of the composite materials was 20%, 30% and 40%. The solid-phase formed specimens were pre-strained to 10%,20%. and 30% strain levels. The forming temperatures of specimens were
. Izod impact test was performed with unnotched specimens. With increasing the glass fiber content ; the impact strength was increased
Effect of Diffusion on the Interfacial Adhesion of Poly(hydroxy ether) Coated Caron Fibers
Composites Research, volume 12, issue 6, 1999, Pages 15~21
Carbon fibers were coated with carboxy modified poly(hydroxy ether)(C-PHE, water dispersed), water soluble polymers poly(hydroxy ether ethanol amine)(PHEA) or water insoluble poly(hydroxy ether)(PHE). Interfacial shear strength of polymer coated carbon fibers was measured by micro-droplet tests with vinyl ester resin, and approximately 30 samples were tested. The interfacial adhesion of poly-mers to carbon fibers was also evaluated, and diffusion behavior of polymer films in vinyl ester resin was investigated. The carbon fibers after testing and diffusion samples were analysed by SEM in order to understand adhesion mechanism. Interfacial shear strength of carbon fibers was enhanced by the coating of PHE and C-PHE which have good or marginal solubility in vinyl ester resin, respectively, but not by the coating of PHEA possibly due to the poor solubility in vinyl ester resin.
A Study on Microscopic Deformation Behaviors of
Superconducting Composite Tape using Acoustic Emission Technique
Composites Research, volume 12, issue 6, 1999, Pages 22~30
Since the surface diffusion processed
superconducting tape has the advantage of having large overall critical current density. it is used for the construction of open type MRI superconducting magnets. However one of the disadvantages of this tape is that
compound often exhibited multiple cracking due to its intrinsic brittleness when subjected to mechanical loading such as bending and winding during the fabrication process for superconducting coil. This will eventually cause the severe degradation of critical current density. Therefore it is important to understand the microscopic deformation behavior of this kind of superconducting tape under the mechanical loading.In this study, acoustic emission(AE) was used to clarify microscopic deformation behavior at room temperature for
superconducting tape which was strengthened and stabilized with copper. For this purpose, special attention was paid to AE characteristics including AE event, energy, and amplitude distribution which were associated with microscopic mechanism of deformation of
superconducting tape under tensile load.
Structural Performance Improvement of Composite Plates By Using Curvilinear Fiber Format
Composites Research, volume 12, issue 6, 1999, Pages 31~42
In aerospace industry, the improvement of structural performance of fight structure without increasing weight has great advantage. In this study. an innovative design method to increase the buckling load and tension failure load at the same time without increasing the weight of composite plates was investigated. By using the curvilinear fiber format a method to increase the buckling load and tension failure load simultaneously was investigated for composite plates with central hole with finite element method. It was investigated how much gain can be obtained with curvilinear fiber format for the plates with different hole size and different stacking sequence. And, for the cases studied, the failure mechanism was also investigated. For the manufacturing of the curvilinear fiber format, smoothly and continuously changing fiber path is necessary. In this study, a simple method to find the smoothly changing fiber path by using the fiber angles obtained with finite element method was presented.
Development of Concurrent Engineering System for Design of Composite Structures
Composites Research, volume 12, issue 6, 1999, Pages 43~52
This paper explains the development of a concurrent engineering system for the rlesign of composite structures. The concurrent engineering system is developed to meet the demand for the better quality products with lower production cost and time. In this study, to compose the architecture of concurrent engineering system, the commercial and noncommercial programs related to design and analysis of composite structures are surveyed and classified. The concurrent engineering system is including various design modules such as design/analysis of composite structures using CLPT and FEM, buckling and post bucking analysis, thermo-elastic analysis of carbon-carbon composite, and optimum design using expert system and genetic algorithm. For the integration and management of softwares, the concurrent engineering system is realized by Microsoft visual
that provide multi-tasking and graphic user interface environment.
Microstructural Morphology and Bending Performance Evaluation of Molded Microcomposites of Thermotropic LCP and PA6
Composites Research, volume 12, issue 6, 1999, Pages 53~64
Microstructural morphology and bending strengths of moulded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) have been studied as a function of epoxy fraction. Injection-moulding of a composite plaque at a temperature below the melting point of the LCP fibrils generated a multi-layered structure: the surface skin layer with thickness of
exhibiting a transverse orientation; the sub-skin layer with an orientation in the flow direction; the core layer with arc-curved flow patterns. The plaques containing epoxy 4.8vol% exhibited superior bending strength and large fracture strain. With an increase of epoxy fraction equal to and beyond 4.8vol%, geometry of LCP domains was changed from fibrillar shape to lamella-like one, which caused a shear-mode fracture. An analysis of the bending strength of the composite plaques by using a symmetric layered model beam suggested that addition of epoxy component altered not only the microstructural geometry but also the elastic moduli and strengths of the respective layers.
Crippling Analysis of Z-Section Composite Stringers
Composites Research, volume 12, issue 6, 1999, Pages 65~73
Crippling stress and failure behavior of Z-section graphite/epoxy composite laminated stringers are investigated by the nonlinear finite element method. Stringers are idealized using 9-node laminated shell element. The complete unloading model is introduced into the finite element method for the progressive failure analysis. A modified Riks method is used to trace the post-failure equilibrium path after local buckling. Finite element results are validated with previous experimental results. The results show that the most important parameter affecting the crippling stress of Z-section stringers is the flange width. In terms of stacking sequence. the highest cripping stress is found at the stringer with
Static and Fatigue Characteristics of Urethane Foam Cored Sandwich Structures
Composites Research, volume 12, issue 6, 1999, Pages 74~82
The static and fatigue characteristics of polyurethane foam cored sandwich structures are investigated. Three types of the specimens with the glass fabric faces and the polyurethane foam core are used; non-stitched. stitched, and stiffened sandwich specimen. Especially additional structural reinforcements with the twisted polyester and glass fiber for thickness direction are made to stitched sandwich structure panel to minimize the delamination of structure which is stitched the upper and lower faces through the core and the resin is impregnated Into stitched fiber with the characteristics of low viscosity of resin at resin flow temperature and cured together with during the curing process. Bending strength of stitched specimen which is 50 mm
pitched is improved by 50 % as com-pared with non-stitched specimen and stiffened specimen is improved 10 times more than non-stitched structure. After fatigue testing of
cycles by 20% of ultimate load under monotonic load, the bending fatigue strength of non-stitched specimen is decreased by 27% of monotonic bending strength, 39% for stitched structure and 20% for stiffened specimen. To verify the aging effect of polyurethane form core, Ultrasonic C-scanning equipment is used to detect the damage of skin laminate alone after fatigue test. From results of UT C-scan images, there is no defect that can be damaged occurred during fatigue test. It is concluded that the decrease of bending strength for foam cored sandwich specimen is caused by the decrease of stiffness due to the aging of polyurethane foam core during fatigue cycles.
Effect of Rubber Particle Size and Polymer Properties on Impact Strength and Fracture Behavior of Rubber/Polymer Composites
Composites Research, volume 12, issue 6, 1999, Pages 83~89
The impact strength and fracture behavior of rubber/polymer composites were investigated with respect to two factors: (i) characteristic ratio,
as a measure of chain flexibility of the polymer matrix and (ii) the rubber particle size in polymer blend system. In this study C was controlled by the composition ratio of polyphenylene oxide (PPO) and polystyene (PS). Izod impact test and fractographic observation of the fracture surface using scanning electron microscope were conducted. Finite element analysis were carried out to gain understanding of plastic deformation mechanism (shear yielding and crazing) of these materials. Shear yielding was found to be enhanced when the flexibility of matrix polymer was relatively low and the rubber particles were small.