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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
The Korean Society for Composite Materials
Editor in Chief :
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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A Study on Fatigue Crack Retardation Using NDT Test in a Hybrid Composite Material Reinforced with a CFRP
Composites Research, volume 12, issue 3, 1999, Pages 1~7
New hybrid composite material CPAL(Carbon Patched ALuminum alloy), an Al2024-T3 plate doubleside reinforced with carbon/epoxy laminates were made. Fatigue crack growth tests were carried out at R=0.2, 0.5 in the CPAL specimens. The retardation mechanism and behavior of fatigue crack growth were examined basing on investigation of the crack and the delamination using a X-Ray and a ultrasonic C-Scan. The fatigue crack growth rates of CPAL specimens were remarkedly retarded compared to that of the Al2024-T3 specimen. The retardations amounts of the fatigue crack growth rates get higher in
CPAL specimen than in
CPAL specimen, and get higher at R=0.2 than at R=0.5. The retardation of fatigue crack growth rates in CPAL specimen was generated by the crack bridging mechanism, that is the behavior that the fibers in CFRP layers decrease the COD in the Al2024-T3 plate.
Mechanical Properties of Carbon Fiber/Si/SiC and Carbon Fiber/C/SiC Composites
Composites Research, volume 12, issue 3, 1999, Pages 8~16
Carbon woven fabric/C/SiC composites were fabricated by multiple impregnations of carbon woven fabric/carbon preform with the polymer precursor of SiC, i.e., polycarbosilane. In addition, two kinds of low density carbon/carbon preforms which had different fiber volume fraction and fiber orientation, i.e., a carbon woven fabric(
55 vol%)/carbon and a chopped carbon fiber
40 vol%)/carbon composites, were reaction-bonded with a silicon melt at 1
in a vacuum to fabricate dense carbon fiber/Si/SiC composites. The reaction-bonding process increased the density to ~2.1 g/
from 1.6 g/
and 1.15 g/
of a carbon woven and a chopped carbon preforms, respectively. All of the composites fractured with extensive fiber pull-out. The higher the density the higher the stiffness and proportional limit stress. The mechanical properties obtained from a three-point bend and tension tests were compared. The ratios of the peak tensile stresses to the bending strengths of a carbon woven and a chopped carbon composites were about one-third, respectively. The carbon woven fabric/Si/SiC composites with density of 2.06 g/
showed ~120 MPa of ultimate strength and ~80 MPa of proportional limit in bend testing.
Buckling Behavior of Elastically Restrained Orthotropic Plates
Composites Research, volume 12, issue 3, 1999, Pages 17~25
In this paper, we present the analytical study results of buckling behavior of elastically restrained orthotropic plates. In the study the boundary conditions of the plate are simply supported at all four edges and elastically restrained by the elastic medium at opposite two longitudinal edges. The energy method is employed in the solution of the problems in which method the buckling coefficient is calculated from the condition that the work-done by the external forces during buckling is equal to the stored elastic strain energy. The results are presented in the graphical from. The equations derived for the orthotropic plate in this study are compared with existing isotropic ones and identical results were observed.
Study of Fatigue Behavior of Repaired Composites
Composites Research, volume 12, issue 3, 1999, Pages 26~35
The static strength and fatigue life of repaired graphite/epoxy laminates are observed using tensile coupon. The lay-up of investigated laminates was [
. Static strength was measured from the specimens prepared by various repair techniques such as precured-single patch, precured-double patch and cure-in-place methods. The strength was recovered to the extent of 60~80 % of unnotched case. Fatigue life was also measured from the laminates repaired with cure-in-place method. Hwang and Han's MFLPE 1(modified fatigue life prediction equation 1), which was based on the fatigue modulus degradation model and reference modulus, was chosen for fatigue life prediction of repaired specimen and compared with the conventional fatigue life equation such as S-N curve and Basquin's relation. The MFLPE 1 has better agreement with experimental data than S-N curve and Basquin's relation.
composites by in-situ Reaction Process of Molten Al
Composites Research, volume 12, issue 3, 1999, Pages 36~44
The fabrication process of
composite by in-situ process was investigated. The effects of processing variables such as addition type and content of Mg, processing temperature and time on the infiltration behavior of molten Al, microstructure and hardness were investigated. When the pure Al was infiltrated into mixtures of Mg and
powder, processing temperature required to spontaneous infiltration was decreased, and the content of Mg was the most powerful variable for infiltration of molten Al. But when the Al-Mg alloy was infiltrated into
particles, infiltration ratio indicated nearly same value regardless of Mg content in alloy and processing temperature, and critical processing temperature required to spontaneous infiltration was
composites which were fabricated by mixtures of Mg and
powders resulted in high hardness value, but hardness values were scattered due to non uniform dispersion of
particles by excessive reaction of Mg.
Buckling and Postbuckling Control of a Composite Beam with Embedded SMA Wire Actuators
Composites Research, volume 12, issue 3, 1999, Pages 45~54
In this paper, an experimental study on the buckling and postbuckling control of a laminated composite beam with eccentrically embedded SMA wire actuators is performed. For the purpose of enhancing the critical buckling load, buckling control is investigated through the use of reactive moment associated with the shape recovery force of SMA wire actuators. To improve the control authority for the buckling and postbuckling control of the SMA-composite beam, closed-loop control is used. The buckling and postbuckling control behaviours are presented and discussed qualitatively and quantitatively on loaddeflection plots considering the stacking sequence of the laminate, slenderness ratio of the beam and activation conditions of the SMA wire actuators. By maintaining the desired deflection shape with the proper reactive moment, buckling control can be extended to the postbuckling of the SMA-composite beam subjected to an external load.
A study on the Thermal Buckling and Postbuckling of a Laminated Composite Beam with Embedded SMA Actuators
Composites Research, volume 12, issue 3, 1999, Pages 55~65
In this paper, the thermal buckling and postbuckling behaviour of composite beam with embedded shape memory alloy (SMA) wires are investigated experimentally and analytically. The results of thermal buckling tests on uniformly heated, clamped, composite beam embedded with SMA wire actuators are presented and discussed in consideration of geometric imperfections, slenderness ratio of beam and embedding position of SMA wire actuators. The shape recovery force can reduce the thermal expansion of composite laminated beam, which result in increment of the critical buckling temperature and reduction of the lateral deflection of postbuckling behaviours. It is presented quantitatively on the temperature-load-deflection behaviour records how the shape recovery force affects the thermal buckling. The cross tangential method is suggested to calculate the critical buckling temperature on the temperature-deflection plot. Based on the experimental analysis, the new formula is also proposed to describe the critical buckling temperature of a laminated composite beam with embedded SMA wire actuators.
Strain Energy Release Rate of Carbon/Epoxy Composite Material under Mixed Mode Delamination
Composites Research, volume 12, issue 3, 1999, Pages 66~74
A modified mixed mode bending test was performed to investigate the mixed mode delamination for carbon/epoxy composite material. Various mixed mode ratios could be produced by changing the applied load position on the loading lever and the bending load position on the specimen. The modified mixed mode bending test was analyzed to obtain strain energy release rates using beam theory, compliance method and finite element method, This results were in good agreement with the experimental result, which confirmed the validity of this test.
Analysis of Thermal Conductivities of Carbon/Phenolic and Silica/Phenolic Ablative Composites by Laser Pulse Method
Composites Research, volume 12, issue 3, 1999, Pages 75~83
The thermal properties of carbon/phenolic and silica/phenolic ablative composites were investigated by measuring the heat capacity, thermal diffusivity and thermal conductivity. The heat capacities of carbon/ phenolic and silica/phenolic composites were calculated from differential scanning calorimeter curve. The thermal diffusivities of carbon/phenolic and silica/phenolic composites were measured by the laser flash method with varying laminated direction, i.e., with laminar direction and across laminar direction. The thermal diffusivities decreased with increasing temperature. The thermal conductivities of carbon/phenolic and silica/phenolic composites were calculated using the heat capacity, density and thermal diffusivity. The thermal conductivities increased with increasing temperature. The thermal conductivity of with laminar direction is two times higher than that of across-laminar direction in carbon/phenolic composite due to the directionality of thermal conductivity of carbon fiber. The thermal conductivities of two dimensional fiber reinforced composites were analyzed using the conductivities of constituents and volume fraction of each constituent. The thermal conductivities of carbon fiber and silica fiber were calculated from thermal conductivities of carbon/phenolic and silica/phenolic composites. The thermal conductivities of carbon/phenolic and silica/phenolic composites at RT were predicted from thermal conductivities of fiber and resin with varying the volume fraction of fiber.
The Effects of Insoluble Polymers on Water Stability of Carbon Fiber Reinforced Polymer-MDF Cementitious Composites
Composites Research, volume 12, issue 3, 1999, Pages 84~90
High alumina cement(HAC) and polyvinyl alcohol(PVA) based macro-defect-free(MDF) cement composites were reinforced using short carbon fibers, 3mm in length, 1-4% in weight fraction and insoluble polymers such as polyurethane, epoxy, phenol resin, in order to increase mechanical properties and water stability. The specimens were manufactured by the low heat-press(warmpress) method. In addition, the interface and the cross-linking reaction of cement and polymers was also studied by the SEM and TEM. Flexural strength of HAC/PVA based MDF cementitious composites was proportionally decreased with increasing fiber contents due to the undensified structure around fibers. The flexural strength of insoluble polymer added specimen was decreased with increasing fiber contents, while water stability was dramatically improved. Epoxy resin added specimen showed the highest strength with increasing fiber contents, compared with other specimens. The water stability of fiber content 4% added specimen immersed in water presented about 95%, 87% at 3 and 7 days immersed in water, respectively. The interfacial adhesive strength of fiber-matrix was very much improved due to cross linking reaction of polymer and metal ions of cement. Tensile strength of insoluble polymers added composites as linearly increased with increasing the fiber contents. The epoxy resin added specimen also showed highest tensile strength. The 4% fiber added specimen presented 30~80% higher strength than controlled specimen.