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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 28, Issue 6 - Dec 2015
Volume 28, Issue 5 - Oct 2015
Volume 28, Issue 4 - Aug 2015
Volume 28, Issue 3 - Jun 2015
Volume 28, Issue 2 - Apr 2015
Volume 28, Issue 1 - Feb 2015
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Damage Visualization of Filament Wound Composite Hydrogen Fuel Tank Using Ultrasonic Propagation Imager
Lee, Jung-Ryul ; Jeong, Hyomi ; Chung, Truong Thanh ; Shin, Hejin ; Park, Jaeyoon ;
Composites Research, volume 28, issue 4, 2015, Pages 143~147
DOI : 10.7234/composres.2015.28.4.143
This paper proposes laser ultrasonic technique for the impact damage inspection of hydrogen fuel tank and proves that the impact damage can be visualized using an ultrasonic wave propagation imager with an easy detachable sensor head as an impact damage inspection tool for hydrogen fuel tanks. Also the performances of the proposed ultrasonic propagation imager support it can be implemented in real-world technology when the hydrogen car becomes popular.
Validation of Piezoelectric Sensor Diagnostics Algorithm Using Instantaneous Baseline Data
Jo, HyeJin ; Jung, Hwee Kwon ; Park, Tong il ; Park, Gyuhae ;
Composites Research, volume 28, issue 4, 2015, Pages 148~154
DOI : 10.7234/composres.2015.28.4.148
In order to detect damage in early stages and properly maintaining structures, the structural health monitoring technology is employed. In most cases, active-sensing SHM needs many piezoelectric (PZT) sensors and actuators. Thus, if there is a defect on PZT used for active-sensing SHM, the structural status could be misclassified. This study, for reliable SHM performance, investigated to detect defects of sensors by using the admittance-based sensor diagnostics. This study also introduced an algorithm that can diagnose sensor defects based only on data measured from the sensors in case that information about the changes in adhesive and environmental investigation, this study confirms that the proposed algorithm could be efficiently applied to real-world structures in which a significant temperature variation could take place.
Manufacturing Method for Sensor-Structure Integrated Composite Structure
Han, Dae-Hyun ; Kang, Lae-Hyong ; Thayer, Jordan ; Farrar, Charles ;
Composites Research, volume 28, issue 4, 2015, Pages 155~161
DOI : 10.7234/composres.2015.28.4.155
A composite structure was fabricated with embedded impact detection capabilities for applications in Structural Health Monitoring (SHM). By embedding sensor functionality in the composite, the structure can successfully perform impact localization in real time. Smart resin, composed of
(PNN-PZT) powder and epoxy resin with 1:30 wt%, was used instead of conventional epoxy resin in order to activate the sensor function in the composite structure. The embedded impact sensor in the composite was fabricated using Hand Lay-up and Vacuum Assisted Resin Transfer Molding(VARTM) methods to inject the smart resin into the glass-fiber fabric. The electrodes were fabricated using silver paste on both the upper and bottom sides of the specimen, then poling treatment was conducted to activate the sensor function using a high voltage amplifier at 4 kV/mm for 30 min at room temperature. The composite's piezoelectric sensitivity was measured to be 35.13 mV/N by comparing the impact force signals from an impact hammer with the corresponding output voltage from the sensor. Because impact sensor functionality was successfully embedded in the composite structure, various applications of this technique in the SHM industry are anticipated. In particular, impact localization on large-scale composite structures with complex geometries is feasible using this composite embedded impact sensor.
Thermal Characteristics of Hybrid Insert for Carbon Composite Satellite Structures
Lim, Jun Woo ;
Composites Research, volume 28, issue 4, 2015, Pages 162~167
DOI : 10.7234/composres.2015.28.4.162
Composite sandwich structures are widely employed in various applications, due to their high specific stiffness and specific bending strength compared to solid panels. Lately, for that reason, the advanced composite sandwich structures are employed in satellite structures: materials should be as light as possible with the highest attainable performance. This study is majorly focused on inserts employed to the composite sandwich satellite structures. A new hybrid insert design was developed in precedent study to reduce the mass of the sandwich structure since the mass of the satellite structure is related to high launching cost . In this study, the thermal characteristics and behavior of the precedently developed hybrid insert with carbon composite reinforcing web and the conventional partial insert were numerically investigated.
Fabrication and Characterization of the Carbon Fiber Composite Sheets
Lee, Yun-Seon ; Song, Seung-A ; Kim, Wan Jin ; Kim, Seong-Su ; Jung, Yong-Sik ;
Composites Research, volume 28, issue 4, 2015, Pages 168~175
DOI : 10.7234/composres.2015.28.4.168
Recently, the applications of carbon fiber reinforced plastics (CFRPs) have become broader than ever when it comes to such industries as automotive, ships, aerospace and military because of their lightweight-ness and high mechanical properties. Thermosetting plastics like epoxy are frequently used as the binding matrix in CFRPs due to their high hardness, wetting characteristics and low viscosity. However, they cannot melted and remolded. For this reason, thermosetting plastic wastes have caused serious environmental problems with the production of fiber reinforced plastics. Thus, many studies have focused on the carbon fiber reinforced thermoplastics (CFRTPs) and recycling carbon fiber. In this study, recycled carbon fiber (RCF) was prepared from CFRPs using a pyrolysis method, which was employed to separate resin and carbon fiber. The degree of decomposition for epoxy resin was confirmed from thermal gravimetric analysis (TGA) and scanning electron microscope (SEM). The RCF was cut and ground to prepare a carbon fiber composite sheet (CFCS). CFCS was manufactured by applying recycled carbon fibers and various thermoplastic fibers. Various characterizations were performed, including morphological analyses of surface and cross-section, mechanical properties, and crystallization enthalpy of CFCS at different cooling conditions.
Energy Absorption Characteristics of Z-shape Fabric under High Velocity Impact
Choi, Chunghyeon ; Park, Yurim ; Kim, YunHo ; Noh, Jae-young ; Kim, Chun-Gon ;
Composites Research, volume 28, issue 4, 2015, Pages 176~181
DOI : 10.7234/composres.2015.28.4.176
In this study, the Z-shape fabric design is proposed as the way to enhance the ballistic performance of fabrics which are used as the intermediate layer of stuffed Whipple shield configurations. The Z-shape fabric employs a different boundary condition from those of conventional configurations of fabrics which include 4 edge fixed. Impact analysis on Z-shape aramid yarns and fabrics using LS-DYNA software was performed and the results were compared with 2 edge fixed and 4 edge fixed fabrics to identify the high velocity impact energy absorption characteristics of the Z-shape fabric. It was revealed that the Z-shape showed different impact behavior and higher energy absorption performance than 2 and 4 edge fixed fabrics.
Cumulative Damage Theory in Fatigue of Graphite/Epoxy [±45]
An, Deuk Man ;
Composites Research, volume 28, issue 4, 2015, Pages 182~190
DOI : 10.7234/composres.2015.28.4.182
The phenomenological evolution laws of damage can be defined either based on residual life or residual strength. The failure of a specimen can be defined immediately after or before fracture. The former is called in this paper by "failure defined by approach I" and the latter "failure defined by approach II." Usually at failure there is a discontinuity of loading variables and, because of this, damage at failure is discontinuous. Therefore the values of damage at failure by two different approaches are not the same. Based on this idea the sequence effects of the phenomenological evolution law of damage given by
were studied. Thin-walled graphite/epoxy tubes consisting of four of
laminates were used for the experimental study of sequence effects and the effects of mean stress on fatigue life. It was found that the sequence effects in two step uniaxial fatigue for
graphite/epoxy tubular specimen showed that a high-low block loading sequence was less damaging than a low-high one.
A Fracture Study on the Bonded DCB Specimen of the Mode III Type with Aluminum Foam
Lee, Jung-Ho ; Cho, Jae-Ung ; Cheon, Seong-Sik ;
Composites Research, volume 28, issue 4, 2015, Pages 191~196
DOI : 10.7234/composres.2015.28.4.191
In this study, the static analysis and experiment were carried out on DCB specimens manufactured with aluminum foam in order to investigate the fracture toughness at the adhesive joint of the structure bonded with adhesive. In case of static analysis, all specimen models were shown to have the maximum reaction force when the forced displacement proceeded as much as 5 mm. The maximum reaction forces became 0.25 kN, 0.28 kN and 0.5 kN respectively in cases of specimen thicknesses of 35 mm, 45 mm and 55 mm. Two specimens in case of static experiment were selected to verify these analysis results. The maximum reaction forces were shown when the forced displacement proceeded as much as 5 to 6 mm. The maximum reaction forces became 0.22 kN and 0.3 kN respectively in cases of specimen thicknesses of 35 mm and 45 mm. By comparing the derived results, it could be shown that there was not much difference between the data of analyses and experiments. Therefore, It is inferred that the study data can be secured with only analysis by no extra experimental procedure. It is thought that the mechanical properties at the structure bonded of DCB with the type of mode III can be analyzed systematically.
Study of Mechanism for Improving Tensile Elastic Modulus of Self-reinforced Composite
Yun, Deok Woo ; Kang, Hyun Min ;
Composites Research, volume 28, issue 4, 2015, Pages 197~203
DOI : 10.7234/composres.2015.28.4.197
Tensile properties of polypropylene based self-reinforced composites were investigated as a function of process variables of the double-belt lamination equipment such as pressure, temperature and cooling conditions. Elastic modulus was enhanced approximately 6 times from 0.2 to 1.2 GPa. The improvement mechanism was studied by identification of crystalline structure changes using DSC and XRD analysis. In addition, morphology change of self-reinforced composites was also investigated by SEM analysis in order to reveal the degree of impregnation.
Strain Recovery Analysis of Non-uniform Composite Beam with Arbitrary Cross-section and Material Distribution Using VABS
Jang, Jun Hwan ; Ahn, Sang Ho ;
Composites Research, volume 28, issue 4, 2015, Pages 204~211
DOI : 10.7234/composres.2015.28.4.204
This paper presents a theory related to a two-dimensional linear cross-sectional analysis, recovery relationship and a one-dimensional nonlinear beam analysis for composite wing structure with initial twist. Using VABS including a related theory, the design process of the composite rotor blade has been described. Cross-sectional analysis was performed at cutting point including all the details of geometry and material. Stiffness matrix and mass matrix were linked to each section to make 1D beam model. The 3D strain distributions within the structure were recovered based on the global behavior of the 1D beam analysis and visualize numerical results.
Manufacturing and Structural Analysis of Thick Composite Spar Using AFP Machine
Kim, Ji-Hyeon ; Han, Jun-Su ; Bae, Byung-Hwan ; Choi, Jin-Ho ; Kweon, Jin-Hwe ;
Composites Research, volume 28, issue 4, 2015, Pages 212~218
DOI : 10.7234/composres.2015.28.4.212
A large composite spar was manufactured using an automatic fiber placement (AFP) machine. To verify its structural performance, the weakest part of the structure, which is called 'corner radius', was tested under bending and examined by finite element analysis. Since the application of AFP machine to composite structure fabrication is still in early stage in Korea, this paper presents the summary of whole process for manufacturing composite spar using AFP machine from mandrel design and analysis to verification test. The deflection and stress by mandrel weight and AFP machine force, thermal deformation and natural frequency were all examined for mandrel design. The target structure was composite C-spar and cured in an autoclave. Test results were compared with nonlinear finite element analysis results to show that the structure has the strength close to the theoretical value. It was confirmed that the corner radius of the spar manufactured by AFP process showed deviation less than 20% compared with first ply failure strength. The results indicate that the AFP technology could be used for large scale composite structure production in the near future.
Joint Design and Strength Evaluation of Composite Air Spoiler for Ship
Pi, June-Woo ; Jeon, Sang-Bae ; Lee, Guen-Ho ; Jo, Young-Dae ; Choi, Jin-Ho ; Kweon, Jin-Hwe ;
Composites Research, volume 28, issue 4, 2015, Pages 219~225
DOI : 10.7234/composres.2015.28.4.219
Air spoiler, which can reduce the drag during operation, can be considered as a possible means to reduce carbon dioxide emission and to increase fuel efficiency. In this study, a composite air spoiler was designed and tested by static and repeated loads. The Green Water Pressure of 0.1 MPa a ship experiences during operation was perpendicularly applied to the air spoiler. Air spoiler was manufactured with sandwich panel which has glass fabric face and balsa core. Multiple sandwich panels were assembled to steel frame by bolt joint. The joint was designed to have bearing failure and examined by static and fatigue tests. Tests showed that the designed joint has enough margin of safety to endure joint failure. The developed sandwich panel to air spoiler is planned to be applied to a large scale commercial ship.
A Study on the Applicability of CNT/Aluminum Nanocomposites to Automotive Parts
Min, Byung Ho ; Nam, Dong Hoon ; Park, Hoon Mo ; Lee, Kyung Moon ; Lee, Jong Kook ;
Composites Research, volume 28, issue 4, 2015, Pages 226~231
DOI : 10.7234/composres.2015.28.4.226
Various characteristics(thermal expansion, microstructure, etc.) and mechanical properties of CNT-aluminum nano composites manufactured by volume production system were evaluated. Also, formability and durability were evaluated for potential applications in automotive parts, via compared with high-elasticity material (A390) and the current commercial product. As a result, this composite has excellent mechanical properties and formability, therefore, to verity its potential for application as light and high strength materials in automobile part.
Prediction of Wetting and Interfacial Property of CNT Reinforced Epoxy on CF Tow Using Electrical Resistance Method
Kwon, Dong-Jun ; Choi, Jin-Yeong ; Shin, Pyeong-Su ; Lee, Hyung-Ik ; Lee, Min-Gyeong ; Park, Jong-Kyoo ; Park, Joung-Man ;
Composites Research, volume 28, issue 4, 2015, Pages 232~238
DOI : 10.7234/composres.2015.28.4.232
As a new method to predict the degree of dispersion in carbon nanocomposites, the electrical resistance (ER) method has been evaluated. After CNT epoxy resin was dropped on CF tow, the change in electrical resistance of carbon fiber tow was measured to evaluate dispersion condition in CNT epoxy resin. Good dispersion of CNTs in carbon nanocomposite exhibited low change in ER due to wetted resin penetrated on CF tow. However, because CNT network was formed among CFs, non-uniform dispersion occurred due to nanoparticle filtering effect by CF tow. The change in ER for poor dispersion exhibited large ER signal change. The change in ER was used for the dispersion evaluation of CNT epoxy resin. Correlation between interlaminar shear strength (ILSS) and dispersion condition by ER method was established. Good CNT dispersion in nanocomposites led to good interfacial properties of fiberreinforced nanocomposites.
Enhancement of the Mechanical Properties of CNT Fibers Synthesized by Direct Spinning Method with Various Post-Treatments
Kim, Jin-seok ; Park, Junbeom ; Kim, Seung Min ; Kwac, L.K ; Hwang, Jun Yeon ;
Composites Research, volume 28, issue 4, 2015, Pages 239~243
DOI : 10.7234/composres.2015.28.4.239
Recent studies regarding the properties of carbon nanotubes (CNT) have made remarkable progress in CNT fibers research. However no CNT fibers showed the properties of CNTs because CNTs in fibers have weak interfacial bonding with low shear modulus in the pristine form. Thus, it is upmost interest to develop and employ post-production treatments to the CNT fibers that would potentially improve their properties. In this study, post-treatments resulted in improvement of strength of CNT fibers up to 40%.
Analyses of Influence of Frictional Heat on the Contact Stress of High-speed Micro-gears
Kim, Cheol ; Kim, Hyeong-Seok ;
Composites Research, volume 28, issue 4, 2015, Pages 244~248
DOI : 10.7234/composres.2015.28.4.244
When a small gear rotates at a very high speed over 40,000 rpm, frictional heat is generated on the gear surfaces. Thermal deformations and stresses arising from frictional heat may lower the efficiency and fatigue life of the high-speed gear. Especially, such frictional heat has much stronger effects on the performance of millimeter-sized high-speed gears used for surgical and dental hand-pieces, due to a small surface area. An analytical equation was derived to calculate frictional temperature on a mating gear surface and conduction heat transfer analysis was performed. Thermal deformation and contact stresses were then calculated using FEM for gears used for medical hand-pieces. The contact stresses of the meshed gear and pinion increase by 19.4% and 16.4%, respectively, when the frictional thermal deformations are considered.