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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 14, Issue 6 - Dec 2001
Volume 14, Issue 5 - Oct 2001
Volume 14, Issue 4 - Aug 2001
Volume 14, Issue 3 - Jun 2001
Volume 14, Issue 2 - Apr 2001
Volume 14, Issue 1 - Feb 2001
Selecting the target year
Vibration Characterization of Cross-ply Laminates Beam with Fatigue Damage
Composites Research, volume 14, issue 3, 2001, Pages 1~9
A new non-destructive fatigue prediction model of the composite laminates is developed. The natural frequencies of fatigue-damaged laminates under extensional loading are related to the fatigue life of the laminates by establishing the equivalent flexural stiffness reduction as a function of the elastic properties of sublaminates. The flexural stiffness is derived by relating the 90-ply elastic modulus reduction, and using the laminate plate theory to the degraded elastic modulus and the intact elastic modulus of other laminates. The natural frequency reduction model, in which the dominant fatigue mode can be identified from the sensitivity scale factors of sublaminate elastic properties, provides natural frequency vs. fatigue cycle curves for the composite laminates. Vibration tests were also conducted on
carbon/epoxy laminates to verify the natural frequency reduction model. Correlations between the predictions of the model and experimental results are good.
Processing and Pressure Test of Filament Wound Composite Pressure Vessels for Oxygen Tanks
Composites Research, volume 14, issue 3, 2001, Pages 10~17
A reseach was peformed to develop composite pressure vessels in conjunction with design, fabrication, and test. Fiber pattern and angels were decided by CADFIL software and they were [
]. Fabrication of bottles were done by 5-axis filament winding machine. During fabrication fiber optic sensors were embedded to measure the strain at points when internal pressure was applied by water pump. Conventional strain gage instrumentation showed the stable test results. The test results were compared to finite element analysis results and they were close each other in strain values. One can see the successful design and fabrication of single boss composite vessels.
Nondestructive Evaluation and Microfailure Mechanisms of Single Fibers/Brittle Cement Matrix Composites using Electro-Micromechanical Technique and Acoustic Emission
Composites Research, volume 14, issue 3, 2001, Pages 18~31
Interfacial and microfailure properties of the modified steel, carbon and glass fibers/cement composites were investigated using electro-pullout test under tensile and compressive tests with acoustic emission (AE). The hand-sanded steel composite exhibited higher interfacial shear strength (IFSS) than the untreated and even neoalkoxy zirconate (Zr) treated steel fiber composites. This might be due to the enhanced mechanical interlocking, compared to possible hydrogen or covalent bonds. During curing process, the contact resistivity decreased rapidly at the initial stage and then showed a level-off. Comparing to the untreated case, the contact resistivity of either Zr-treated or hand-sanded steel fiber composites increased to the infinity at latter stage. The number of AE signals of hand-sanded steel fiber composite was much more than those of the untreated and Zr-treated cases due to many interlayer failure signals. AE waveforms for pullout and frictional signals of the hand-sanded composite are larger than those of the untreated case. For dual matrix composite (DMC), AE energy and waveform under compressive loading were much higher and larger than those under tensile loading, due to brittle but well-enduring ceramic nature against compressive stress. Vertical multicrack exhibits fur glass fiber composite under tensile test, whereas buckling failure appeared under compressive loading. Electro-micromechanical technique with AE can be used as an efficient nondestructive (NDT) method to evaluate the interfacial and microfailure mechanisms for conductive fibers/brittle and nontransparent cement composites.
Crippling Test of Z-section Graphite/Epoxy Stringers
Composites Research, volume 14, issue 3, 2001, Pages 32~41
Z-section composite stringers with various lengths and flange-widths are tested in axial compression for the validation of a finite element algorithm to calculate the buckling and crippling stresses of composite laminated stringers. The stacking sequence considered is
. Strain gages are attached to each specimen, and deflection and end-shortening are obtained by two LVDTs. The buckling load is determined from the load vs. strain response, load vs. end-shortening curves, and load vs. out-of-plane deflection curves. The ultimate stress after local buckling is used as the crippling stress. Comparison between finite element and experimental results shows good agreement in the local buckling and crippling stresses.
Modeling of Damage Initiation in Singly Oriented Ply Fiber-Metal Laminate under Concentrated Loading Conditions
Composites Research, volume 14, issue 3, 2001, Pages 42~50
Modeling of damage initiation in singly oriented ply (SOP) Fiber Metal Laminate (FML) under concentrated loading conditions was studied. The finite element method (FEM) base on the first order shear deformation theory is used for th\ulcorner modeling of damage initiation in SOP FML. The failure indices (FI) of the fiber prepreg and the metal laminate were calculated by using the Tasi-Hill failure criterion and the Miser yield criterion, respectively. To verify the present method, the failure analysis was conducted under uniaxial loading and cylindrical bending, then the analysis under concentrated load was conducted. The results show that the analysis is reasonable. An indentation test was conducted to compare a damage initiation load with a calculated FI. The test was conducted under two side clamped conditions to study the fiber orientation effect. Indentation curve was fitted using the Hertz equation and a damage initiation load is defined that the point which deviate the fitted curve from the real indentation curve. The damage initiation loads were obtained under various fiber orientations and compared with calculated FIs. The experiment was well matched with calculated FI. This results shows that the present method is suitable for the damage initiation modeling of SOP FML.
A Study of the Pressure Effect on the Compressive Fracture Toughness of Quasi-Isotropic Composites
Composites Research, volume 14, issue 3, 2001, Pages 51~56
It is known that the elastic modulus, maximum stress, and maximum strain of fiber-reinforced polymer composites are affected by high pressure. Fracture behavior is also known to be affected by high pressure. In this work, the pressure effect on the compressive fracture toughness of thick quasi-isotropic composites was investigated. Dog-bone type specimens of stacking sequence, [0
were used. Compressive fracture tests were conducted under four pressure levels. The pressure levels applied were 0.1 MPa, 100 MPa, 200 MPa, and 300 MPa. Fracture toughness for each pressure level was determined from the compliance method. The results show that the compressive fracture toughness increases with increasing pressure. Specifically, fracture toughness increases 44% as the pressure increases from 0.1 MPa to 300 MPa.
Prediction of Thermal Conductivity of Spatially Reinforced Composites
Composites Research, volume 14, issue 3, 2001, Pages 57~68
This paper predicted the thermal conductivity of spatially reinforced composites(SRC) by applying the volume averaging method and the thermal resistance method. The former method employs existing micro-mechanical theories and conventional transformation rules to obtain the constitutive relations for the unit cells of the composites and the latter one uses the analogy between the diffusion of heat and electrical charge. To verify the theoretical predictions, the thermal conductivity of 4-D(dimensional) SRC was examined experimentally. The comparison of the numerical results with those measured by the experiment showed good agreement.
A Double Cantilever Sandwich Beam Method far Evaluating Frequency Dependence of Dynamic Modulus and Damping Factor of Rubber Materials
Composites Research, volume 14, issue 3, 2001, Pages 69~76
This paper proposes a double cantilever sandwich-beam method fur evaluating the frequency dependence of dynamic characteristics of rubbers. The flexural vibration of a double cantilever sandwich-beam specimen with an inserted rubber layer was studied using a finite element simulation in combination with the sine-sweep test. Quadratic relationships of dynamic elastic modulus and material loss factor of rubbers with frequency were suggested employing the least square error method.
Thermal and Geometrical Effect on the Motor Performance of Composite Squirrel Cage Rotor
Composites Research, volume 14, issue 3, 2001, Pages 77~89
Since the critical whirling vibration frequency of high speed built-in type motor spindle systems is dependent on the rotor mass of the built-in motor and the spindle specific bending modulus, the rotor and the shaft were designed using magnetic powder containing epoxy and high modulus carbon fiber epoxy composite, respectively. In order to increase the amount of the magnetic flux of the composite squirrel cage rotor of an AC induction motor, a steel core was inserted into the composite rotor. From the magnetic analysis, the optimal configurations of steel core and conductor bars for the dynamic characteristics of the rotor system were determined and proposed. The temperature dependence of composite squirrel cage rotor materials was investigated by various experiments such as TMA, DMA and VSM.
Researeh and Development Trends on Application of Piezolectric Materials
Composites Research, volume 14, issue 3, 2001, Pages 90~98
In this survey paper, the application research and development trends of piezoelectric materials are reviewed. Advantages and disadvantages of piezoelectric materials, and the recent research to overcome the drawbacks are discussed. The market of piezoelectric sensors and actuators in USA, Japan, and EU is surveyed with several examples. In Korea, the analytical research concerning piezoelectric materials is active but the developments of devices and equipments are not so active, and the investment in this field is necessary.
(주)태용-한국기계연구원 복합재료그룹 연구원 벤쳐
Composites Research, volume 14, issue 3, 2001, Pages 99~102