• Title, Summary, Keyword: Micromechanical Techniques

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Nondestructive Sensing Evaluation of Ni Nanowire Strands and Carbon Nanotube/Epoxy Composites Using Electro-Micromechanical Techniques (Electro-Micromechanical 시험법을 이용한 Ni Nanowire Strands 및 Carbon Nanotube 강화 에폭시 복합재료의 비파괴 감지능 평가)

  • Jung, Jin-Gyu;Kim, Sung-Ju;Park, Joung-Man
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.269-272
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    • 2005
  • Nondestructive damage sensing and load transferring mechanism of Ni nanowire strands and multi-wall carbon nanotube (MWCNT)/epoxy composites were investigated using electro-micromechanical techniques. MWCNT composite was especially prepared for high volume contents, 50 vol % of reinforcement. Electro-micromechanical techniques were applied to measure apparent modulus and contact resistance of Ni nanocomposites with their alignment and different diameters, and adding contents. Applied cyclic load affected on apparent modulus and electrical properties on nanocomposites due to various inherent properties of each CNMs. Contact resistivity on humidity sensing was a good indicator for monitoring as for multifunctional applications. Further study on actuation as well as sensing will be investigated for the following work continuously.

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Interfacial Properties and Curing Behavior of Carbon Fiber/Epoxy Composites using Micromechanical Techniques and Electrical Resistivity Measurement (Micromechanical 시험법과 전기적 고유저항 측정을 이용한 탄소섬유강화복합재료의 계면 물성과 경화거동에 관한 연구)

  • 이상일;박종만
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.17-21
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    • 2000
  • Logarithmic electrical resistivity of the untreated or thin diameter carbon fiber composite increased suddenly to the infinity when the fiber fracture occurred by tensile electro-micromechanical test, whereas that of the ED or thick fiber composite increased relatively broadly up to the infinity. Electrical resistance of single-carbon fiber composite increased suddenly due to electrical disconnection by the fiber fracture in tensile electro-micromechanical test, whereas that of SFC increased stepwise due to the occurrence of the partial electrical contact with increasing the buckling or overlapping in compressive test. Electrical resistivity measurement can be very useful technique to evaluate interfacial properties and to monitor curing behavior of single-carbon fiber/epoxy composite under tensile/compressive loading.

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Interfacial Properties and Microfailure Degradation Mechanisms of Bioabsorbable Composites for Implant Materials using Micromechanical Technique and Acoustic Emission (Micromechanical시험법과 Acoustic Emission을 이용한 Implant용 생흡수성 복합재료의 계면물성과 미세파괴 분해메카니즘)

  • Kim, Dae-Sik;Park, Joung-Man;Kim, Sung-Ryong
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.263-267
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    • 2001
  • The changes of interfacial properties and microfailure degradation mechanisms of bioabsorbable composites with hydrolysis were investigated using micromechanical test and acoustic emission (AE). As hydrolysis time increased, the tensile strength, the modulus and the elongation of PEA and bioactive glass fibers decreased, whereas those of chitosan fiber changed little. Interfacial shear strength (IFSS) of bioactive glass fiber/poly-L-lactide (PLLA) composite was significantly higher than that two other systems. The decreasing rate of IFSS was the fastest in bioactive glass fiber/PLLA composite, whereas that of chitosan fiber/PLLA composite was the slowest. With increasing hydrolysis time, distribution of AE amplitude was narrow, and AE energy decreased gradually.

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Interfacial Evaluation and Damage Sensing of Carbon Fiber/Epoxy-AT-PEI Composite using Electro-Micromechanical Techniques (Electro-micromechanical 시험법을 이용한 탄소섬유 강화 Epoxy-AT PEI 복합재료의 손상 감지능 및 계면물성 평가)

  • Kim, Dae-Sik;Kong, Jin-Woo;Park, Joung-Man;Kim, Minyoung;Kim, Wonho;Ahn, Byung-Hyun;Park, Jin-Ho
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.212-215
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    • 2002
  • Interfacial evaluation and damage sensing of the carbon fiber/epoxy-amine terminated (AT)-polyetherimide (PEI) composites were performed using micromechanical test and electrical resistance measurement. As AT-PEI content increased, the fracture toughness of epoxy-AT-PEI matrix increased, and thus their interfacial shear strength (IFSS) was improved due to the improved toughness. After curing process, the changes in electrical resistance (ΔR) with increasing AT-PEI contents increased gradually because of the changes in thermal expansion coefficient (TEC) and thermal shrinkage of matrix. Matrix fracture toughness was correlated to the IFSS, residual stress and electrical resistance. The results obtained from the electrical resistance measurement during curing process, reversible stress/strain, and durability test were consistent with modified matrix toughness properties.

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Sensing and Interfacial Evaluation of Ni Nanowire Strands/Polymer Composites using Electro-micromechanical Technique (Electro-Micromechanical 시험법을 이용한 Ni Nanowire Strands 강화 고분자 복합재료의 Sensing과 계면 물성 평가)

  • Kim, Sung-Ju;Jung, Jin-Gyu;Park, Joung-Man
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.141-144
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    • 2005
  • Sensing and interfacial evaluation of Ni nanowire strands/polymer composites were investigated using Electro-micromechanical technique. Electro-micromechanical techniques can be used as sensing method for micro damage, loading, temperature of interfacial properties. Using Ni nanowire strands/silicone composites with different content, load sensing response of electrical contact resistivity was investigated under tensile and compression condition. The mechanical properties of Ni nanowire strands with different type/epoxy composites were measured using uniformed cyclic loading and tensile test. Ni nanowire strands/epoxy composites showed humidity and temperature sensing within limited ranges, 20 vol% reinforcement. Some new information on temperature and humidity sensing plus loading sensing of Ni nanowire strands/polymer composites could be obtained from the electrical resistance measurement as a new concept of the nondestructive interfacial evaluation.

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Interfacial Properties of Electrodeposited Carbon Fiber/Epoxy Composites using Electro-Micromechanical Techniques and Nondestructive Evaluations

  • Park, Joung-Man;Lee, Sang-Il
    • Macromolecular Research
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    • v.9 no.1
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    • pp.20-29
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    • 2001
  • Interfacial adhesion and nondestructive behavior of electrodeposited (ED) carbon fiber rein-forced composites were evaluated using electro-micromechanical techniques and acoustic emission (AE). The interfacial shear strength (IFSS) of the ED carbon fiber/epoxy composites was higher than that of the untreated fiber. This might be expected because of the possibility of chemical or hydrogen bonding in an electrically adsorbed polymeric interlayer. The logarithmic electrical resistivity of the untreated single-carbon fiber composite increased suddenly to infinity when fiber fracture occurred, whereas that of the ED composite increased relatively gradually to infinity. This behavior may arise from the retarded fracture time due to enhanced IFSS. In single- and ten-carbon fiber composites, the number of AE signals coming from interlayer failure of the ED carbon fiber composite was much larger than that of the untreated composite. As the number of the each first fiber fractures increased in the ten-carbon fiber composite, the electrical resistivity increased stepwise, and the slope of the logarithmic electrical resistance increased.

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Nondestructive Damage Sensitivity of Carbon Nanotube and Nanofiber/Epoxy Composites Using Electro-Micromechanical Technique and Acoustic Emission (Electro-Micromechanical 시험법과 음향방출을 이용한 탄소 나노튜브와 나노섬유 강화 에폭시 복합재료의 비파괴적 손상 감지능)

  • Kim, Dae-Sik;Park, Joung-Man;Lee, Jae-Rock;Kim, Tae-Wook
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.117-120
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    • 2003
  • Electro-micromechanical techniques were applied using four-probe method for carbon nanotube (CNT) or nanofiber (CNF)/epoxy composites with their content. Carbon black (CB) was used to compare with CNT and CNF. The fracture of carbon fiber was detected by nondestructive acoustic emission (AE) relating to electrical resistivity for double-matrix composites test. Sensing for fiber tension was performed by electro-pullout test under uniform cyclic strain. The sensitivity for fiber damage such as fiber fracture and fiber tension was the highest for CNT/epoxy composites, and in CB case they were the lowest compared with CNT and CNF. Reinforcing effect of CNT obtained from apparent modulus measurement was the highest in the same content. The results obtained from sensing fiber damage were correlated with the morphological observation of nano-scale structure using FE-SEM. The information on fiber damage and matrix deformation and reinforcing effect of carbon nanocomposites could be obtained from electrical resistivity measurement as a new concept of nondestructive evaluation.

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Nondestructive Sensing Evaluation of Thermal Treated Carbon Nanotube and Nanofiber/Epoxy Composites Using Electrical Resistance Measurement (전기저항 측정 방법을 이용한 표면 처리된 탄소 나노튜브와 나노 섬유 강화된 에폭시 복합재료의 비파괴적 감지능 평가)

  • Jung Jin-Kyu;Park Joung-Man;Kim Dae-Sik;Kim Tae-Wook
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.15-18
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    • 2004
  • Nondestructive damage sensing and mechanical properties for thermal treated carbon nanotube(CNT) and nanofiber(CNF)/epoxy composites were investigated using electro-micromechanical technique. Carbon black (CB) was used only for the comparison. Electro-micromechanical techniques were applied to obtain the fiber damage and stress transferring effect of carbon nanocomposites with their contents. Thermal treatment and temperature affected on apparent modulus and electrical properties on nanocomposites due to enhanced inherent properties of each CNMs. Coefficient of variation (COV) of volumetric electrical resistance can be used to obtain the dispersion degree indirectly for various CNMs. Dispersion and surface modification are very important parameters to obtain improved mechanical and electrical properties of CNMs for multifunctional applications. Further optimized functionalization and dispersion conditions will be investigated for the following work continuously.

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Bonding to zirconia with resin cements (지르코니아와 레진 시멘트의 결합)

  • Lim, Bum-Soon;Her, Soo-Bok
    • The Journal of the Korean dental association
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    • v.49 no.5
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    • pp.265-278
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    • 2011
  • The introduction of zirconia-based materials to the dental field broadened the design and application limits of, all-ceramic restorations. Most ceramic restorations are adhesively luted to the prepared tooth, however, resin bonding to zirconia components is less reliable than those to other dental ceramic systems. It is important for high retention, prevention of microleakage, and increased fracture resistance, that bonding techniques be improved for zirconia systems. Strong resin bonding relies on micromechanical interlocking and adhesive chemical bonding to the ceramic surface, requiring surface roughening for mechanical bonding and surface activation for chemical adhesion. In many cases, high strength ceramic restorations do not require adhesive bonding to tooth structure and can be placed using conventional cements which rely only on micromechanical retention. However, resin bonding is desirable in some clinical situations. In addition, it is likely that strong chemical adhesion would lead to enhanced long-term fracture and fatigue resistance in the oral environment.

Nondestructive Evaluation and Interfacial Damage Sensing of PVDF embedded Polymer Composites using Micromechanical Techniques and Acoustic Emission (Micromechanical 시험법과 AE를 이용한 PVDF 함침 고분자 복합재료의 계면손상감지능 및 비파괴적 평가 연구)

  • Kong, Jin-Woo;Park, Joung-Man;Kim, Ki-Bok;Yoon, Dong-Jin
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.216-219
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    • 2002
  • Conventional piezoelectric lead-zirconate-titanate (PZT) senor has high sensitivity, but it is very brittle. Recently polymer films such as polyvinylidene fluoride (PVDF) have been used use as a sensor. The advantages of PVDF are the flexibility and mechanical toughness. Simple process and possible several shapes are also additional advantages. PVDF sensor can be directly embedded and attached to a structure. In this study, PVDF sensor was embedded in single glass fiber/epoxy composites whereas PZT sensor with AE was attached to single fiber composites (SFC). Piezoelectric sensor responds to interfacial damage of SFC. The signals measured by PVDF sensor were compared to PZT sensor. PZT sensor detected the signals of fiber fracture, matrix crack, interfacial debonding and even sensor delamination, whereas PVDF sensor only detected fiber fracture signals so far, because PZT sensor is much more sensitive than current PVDF sensor. Wave voltage of fiber fracture measured by PVDF sensor was lower than that of PZT sensor, but the results of fast Fourier transform (FFT) analysis were same. Wave velocity using two PZT sensors was also studied to know the internal and surface damage effect of epoxy specimens.

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