• Title/Summary/Keyword: Flexible matrix composite

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Vibration Control of Stiffened Hull Structure Using MFC Actuator (MFC 작동기를 이용한 보강 Hull 구조물의 능동 진동 제어)

  • Jeon, Jun-Cheol;Sohn, Jung-Woo;Choi, Seung-Bok
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.7
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    • pp.643-649
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    • 2011
  • This work presents an active vibration control of a stiffened hull structure using a flexible macro fiber composite(MFC) actuator. As first step, the governing equation of the hull structure is derived in a matrix form and its dynamic characteristics such as natural frequency are obtained via a finite element analysis(FEA). The natural frequencies obtained from the FEA are compared with those determined from experimental measurement. After formulating the control model in a state space representation, an optimal controller is designed in order to attenuate the vibration of the stiffened hull structure. The controller is then empirically realized through dSPACE and control responses are evaluated in time domain.

Periodic-Cell Simulations for the Microscopic Damage and Strength Properties of Discontinuous Carbon Fiber-Reinforced Plastic Composites

  • Nishikawa, M.;Okabe, T.;Takeda, N.
    • Advanced Composite Materials
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    • v.18 no.1
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    • pp.77-93
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    • 2009
  • This paper investigated the damage transition mechanism between the fiber-breaking mode and the fiber-avoiding crack mode when the fiber-length is reduced in the unidirectional discontinuous carbon fiber-reinforced-plastics (CFRP) composites. The critical fiber-length for the transition is a key parameter for the manufacturing of flexible and high-strength CFRP composites with thermoset resin, because below this limit, we cannot take full advantage of the superior strength properties of fibers. For this discussion, we presented a numerical model for the microscopic damage and fracture of unidirectional discontinuous fiber-reinforced plastics. The model addressed the microscopic damage generated in these composites; the matrix crack with continuum damage mechanics model and the fiber breakage with the Weibull model for fiber strengths. With this numerical model, the damage transition behavior was discussed when the fiber length was varied. The comparison revealed that the length of discontinuous fibers in composites influences the formation and growth of the cluster of fiber-end damage, which causes the damage mode transition. Since the composite strength is significantly reduced below the critical fiber-length for the transition to fiber-avoiding crack mode, we should understand the damage mode transition appropriately with the analysis on the cluster growth of fiber-end damage.

1-D photonic crystals of free-standing DBR PSi for sensing and drug delivery applications (비고정화 된 일차원 광결정의 DBR 다공성 실리콘을 이용한 센서와 Drug Delivery로의 응용)

  • Koh, Young-Dae;Kim, Ji-Hoon;Park, Jong-Sun;Kim, Sung-Gi;Kim, Dong-Su;Cho, Sung-Dong;Sohn, Hong-Lae
    • Journal of Sensor Science and Technology
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    • v.15 no.6
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    • pp.391-396
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    • 2006
  • Free-standing multilayer distributed Bragg reflectors (DBR) porous silicon dielectric mirrors, prepared by electrochemical etching of crystalline silicon using square wave currents are treated with polystyrene to produce flexible, stable composite materials in which the porous silicon matrix is covered with caffeine-impregnated polystyrene. Optically encoded DBR PSi/polystyrene composite films retain the optical reflectivity. Optical characteristics of DBR PSi/polystyrene composite films are stable and robust for 2 hrs in a pH=7 aqueous buffer solution. The appearance of caffeine and change of DBR peak were simultaneously measured by UV-vis spectrometer and Ocean optics 2000 spectrometer, respectively.

Polymer/Inorganic Nanohybrid Membrane on Lithium Metal Electrode: Effective Control of Surficial Growth of Lithium Layer and Its Improved Electrochemical Performance (리튬 금속 전극상 고분자/무기물 나노복합막 형성: 리튬층의 효과적 표면성장 제어 및 전기화학적 특성 향상)

  • Jeong, Yohan;Seok, Dohyeong;Lee, Sanghyun;Shin, Weon Ho;Sohn, Hiesang
    • Membrane Journal
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    • v.30 no.1
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    • pp.30-37
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    • 2020
  • Polymer/inorganic composites were used as a protective layer of lihitum metal electrode for effective suppression of lithium dendrite. PVDF-HFP was used as an polymer material and TiO2 nanoparticle was used as an inorganic material. PVDF-HFP is a highly flexible polymer that acts as a matrix of inorganic materials while TiO2 nanoparticle improves the mechanical strength and ion conductivity of the protective layer. The as-synthesized protective hybrid membrane exhibited good dispersion of TiO2 in the PVDF-HFP matrix by SEM, AFM and XRD analyses. Furthermore, the electrochemical analysis showed that the polymer-inorganic composite retained high coulombic efficiency of 80% and low overpotential, less than 20 mV until the 100th cycles due to the improved mechanical properties and ion conductivity in comparison to the control sample (untreated and PVDF-HFP polymers/Cu).

Effect of surface treatments on the bond strength of indirect resin composite to resin matrix ceramics

  • Celik, Ersan;Sahin, Sezgi Cinel;Dede, Dogu Omur
    • The Journal of Advanced Prosthodontics
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    • v.11 no.4
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    • pp.223-231
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    • 2019
  • PURPOSE. The purpose of this study was to evaluate the shear bond strength (SBS) of an indirect resin composite (IRC) to the various resin matrix ceramic (RMC) blocks using different surface treatments. MATERIALS AND METHODS. Ninety-nine cubic RMC specimens consisting of a resin nanoceramic (RNC), a polymer-infiltrated hybrid ceramic (PIHC), and a flexible hybrid ceramic (FHC) were divided randomly into three surface treatment subgroups (n = 11). In the experimental groups, untreated (Cnt), tribochemical silica coating (Tbc), and Neodymium-Doped Yttrium Aluminum Garnet (Nd:YAG) laser irradiation (Lsr) with 3 W (150 mJ/pulse, 20 Hz for 20 sec.) were used as surface treatments. An indirect composite resin (IRC) was layered with a disc-shape mold ($2{\times}3mm$) onto the treated-ceramic surfaces and the specimens submitted to thermal cycling (6000 cycles, $5-55^{\circ}C$). The SBS test of specimens was performed using a universal testing machine and the specimens were examined with a scanning electron microscope to determine the failure mode. Data were statistically analyzed with two-way analysis of variance (ANOVA) and Tukey HSD test (${\alpha}=.05$). RESULTS. According to the two-way ANOVA, only the surface treatment parameter was statistically significant (P<.05) on the SBS of IRC to RMC. The SBS values of Lsr-applied RMC groups were significantly higher than Cnt groups for each RMC material, (P<.05). Significant differences were also determined between Tbc surface treatment applied and untreated (Cnt) PIHC materials (P=.039). CONCLUSION. For promoting a reliable bond strength during characterization of RMC with IRC, Nd:YAG laser or Tbc surface treatment technique should be used, putting in consideration the microstructure and composition of RMC materials and appropriate parameters for each material.

DBR PSi/Polymer Composite Materials -Dual Photonic Characteristics (DBR 다공성 실리콘/고분자 Composite 재료-이중적 광학특성)

  • Park, Cheol-Young;Jang, Seung-Hyun;Kim, Ji-Hoon;Park, Jae-Hyun;Koh, Young-Dae;Kim, Sung-Jin;Ko, Young-Chun;Sohn, Hong-Lae
    • Journal of the Korean Vacuum Society
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    • v.16 no.3
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    • pp.221-226
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    • 2007
  • DBR (distributed Bragg reflectors) PSi (porous silicon) composite films displaying dual optical properties, both optical reflectivity and photoluminescence had been developed. DBR PSi samples were prepared by electrochemical etch of heavily doped $p^{++}-type$ silicon wafers (boron doped, polished on the <100> face, resistivity of $0.8-1.2m{\Omega}-cm$, Siltronix, Inc.). Free-standing DBR PSi films were treated with PMMA (polymethyl methacrylate) to produce flexible, stable composite materials in which the PSi matrix is covered with PMMA containing photoluminescent polysiloles. Optical characteristics of DBR PSi/polysilole-impregnated PMMA composite materials exhibit both their photonic reflectivity at 565 nm and photoluminescence at 510 nm, simultaneously. A possible application of this materials will be discussed.

Fiber Reinforced Inlay Adhesion Bridge

  • Cho, Lee-Ra;Yi, Yang-Jin;Song, Ho-Yong
    • The Journal of Korean Academy of Prosthodontics
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    • v.38 no.3
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    • pp.366-374
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    • 2000
  • FRC/ceromer system provides the clinician with a durable, flexible, and esthetic alternative to conventional porcelain fused to metal crowns. FRC is the matrix which is silica-coated and embedded in a resin matrix. The ceromer material which is a second generation indirect composite resin contains silanized, microhybrid inorganic fillers embedded in a light-curing organic matrix. FRC/ceromer restoration has a several advantages: better shock absorption, less wear of occluding teeth, translucency, color stability, bonding ability to dental hard tissues, and resiliency. It has versatility of use including inlay, onlay, single crown, and esthetic veneers. With adhesive technique, it can be used for single tooth replacement in forms of inlay adhesion bridge. In single tooth missing case, conventional PFM bridge has been used for esthetic restoration. However, this restoration has several disadvantages such as high cost, potential framework distortion during fabrication, and difficulty in repairing fractures. Inlay adhesion bridge with FRC/ceromer would be a good alternative treatment plan. This article describes a cases restored with Targis/Vectris inlay adhesion bridge. Tooth preparation guide, fabrication procedure, and cementation procedure of this system will be dealt. The strength/weakness of this restoration will be mentioned, also. If it has been used appropriately in carefully selected case, it can satisfy not only dentist's demand of sparing dental hard tissue but also patient's desire of seeking a esthetic restorations with a natural appearance.

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Development of Thermoplastic Carbon Composite Hybrid Bipolar Plate for Vanadium Redox Flow Batteries (VRFB) (바나듐 레독스 흐름전지용 열가소성 탄소 복합재료 하이브리드 분리판 개발)

  • Jun Woo Lim
    • Composites Research
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    • v.36 no.6
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    • pp.422-428
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    • 2023
  • The electrical contact resistance between the bipolar plate (BP) and the carbon felt electrode (CFE), which are in contact by the stack clamping pressure, has a great impact on the stack efficiency because of the relatively low clamping pressure of the vanadium redox flow battery (VRFB) stack. In this study, a polyethylene (PE) composite-CFE hybrid bipolar plate structure is developed through a local heat welding process to reduce such contact resistance and improve cell performance. The PE matrix of the carbon fiber composite BP is locally melted to create a direct contact structure between the carbon fibers of CFE and the carbon fibers of BP, thereby reducing the electrical contact resistance. Area specific resistance (ASR) and gas permeability are measured to evaluate the performance of the PE composite-CFE hybrid bipolar plate. In addition, an acid aging test is performed to measure stack reliability. Finally, a VFRB unit cell charge/discharge test is performed to compare and analyze the performance of the developed PE composite-CFE hybrid BP and the conventional BP.

Fabrication of Vertically Oriented ZnO Micro-crystals array embedded in Polymeric matrix for Flexible Device (수열합성을 이용한 ZnO 마이크로 구조의 성장 및 전사)

  • Yang, Dong Won;Lee, Won Woo;Park, Won IL
    • Journal of the Microelectronics and Packaging Society
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    • v.24 no.4
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    • pp.31-37
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    • 2017
  • Recently, there has been substantial interest in flexible and wearable devices whose properties and performances are close to conventional devices on hard substrates. Despite the advancement on flexible devices with organic semiconductors or carbon nanotube films, their performances are limited by the carrier scattering at the molecular to molecular or nanotube-to-nanotube junctions. Here in this study, we demonstrate on the vertical semiconductor crystal array embedded in flexible polymer matrix. Such structures can relieve the strain effectively, thereby accommodating large flexural deformation. To achieve such structure, we first established a low-temperature solution-phase synthesis of single crystalline 3D architectures consisting of epitaxially grown ZnO constituent crystals by position and growth direction controlled growth strategy. The ZnO vertical crystal array was integrated into a piece of polydimethylsiloxane (PDMS) substrate, which was then mechanically detached from the hard substrate to achieve the freestanding ZnO-polymer composite. In addition, the characteristics of transferred ZnO were confirmed by additional structural and photoluminescent measurements. The ZnO vertical crystal array embedded in PDMS was further employed as pressure sensor that exhibited an active response to the external pressure, by piezoelectric effect of ZnO crystal.

Micro gadolinium oxide dispersed flexible composites developed for the shielding of thermal neutron/gamma rays

  • Boyu Wang;Xiaolin Guo;Lin Yuan;Qinglong Fang;Xiaojuan Wang;Tianyi Qiu;Caifeng Lai;Qi Wang;Yang Liu
    • Nuclear Engineering and Technology
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    • v.55 no.5
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    • pp.1763-1774
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    • 2023
  • In this study, a series of flexible neutron/gamma shielding composites are fabricated through the doping of Gd2O3 into the matrix of SEBS with (MGd2O3: MSEBS) % from 5% to 100%. Neutron transmittance test shows an exponential attenuation with the increase of areal density of Gd, in which the transmittance T ranges from 59.1440% to 35.3026%, with standard deviation less than 2.2743%, mass attenuation coefficient 𝜇m from 0.3194 cm2/g to 0.4999 cm2/g, and half value layer-HVL value from 2.4530 mm to 1.1313 mm. Shielding efficiency of the Gd2O3/SEBS composites is basically improved in comparison with that of B4C/SEBS. The transmittance T, mass/linear attenuation coefficient 𝜇m and 𝜇, HVL and effective atomic number Zeff for the shielding of γ rays (39 keV, 59 keV and 122 keV) are measured and calculated with XCOM as well as MCX programs. Finally, plots of the three dimensional relationships between transmittance, doping amount and thickness are provided to the guidance for engineering shielding design. In summary, the Gd2O3/SEBS composite is proved to be an effective flexible neutron/low energy γ rays shielding material, which could be of potential applications in the field of nuclear technology and nuclear engineering.