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Rice panicle blast is one of the most serious diseases threatening stable rice production by causing severe damage to rice yields and quality. The disease is easy to occur under low air temperature and frequent heavy rainfall during the heading season of rice. In 2021, a rice panicle blast severely occurred in the Jeonbuk province of Korea. The incidence area of panicle blast accounted for 27.7% of the rice cultivation area of Jeonbuk province in 2021, which was 13.7-times higher than in 2019 and 2.6-times higher than in 2020. This study evaluated the incidence areas of rice panicle blast in each region of Jeonbuk province in 2021. The weather conditions during the heading season of rice, mainly cultivated rice cultivars, and the race diversity of the Jeonbuk isolates were also investigated. It will provide important information for the effective control of the rice panicle blast.

In the present study, carbon nanofibers containing multi-walled carbon nanotubes (MWCNTs) were fabricated using electrospinning and used as an electrode for structural supercapacitors. Electrospun polyacrylonitrile (PAN) nanofibers were converted to carbon nanofibers with stabilization and carbonization processes assisted by thermal treatment. The surface area of the electrospun carbon nanofiber electrodes was further increased several thousand times using an activation process. Multifunctional supercapacitors were fabricated using electrospun carbon nanofibers and a vacuum resin infusion technique. The specific capacitance was dramatically improved due to the decreased equivalent series resistance and increased surface area of the nanofiber electrodes. Moreover, the carbon nanofiber electrodes helped increase interlaminar fracture toughness of structural supercapacitors because it acted like ‘Velcro’ between the fabric interfaces. This work is a ‘proof-of-concept’ for a simple and effective method to produce an electrode for structural supercapacitors based on the electrospinning technique.

Chopped strands of glass fiber reinforced polymerized dicyclopentadiene (p-DCPD) was manufactured and mechanical properties were assessed. For the purpose, a lab-scale long fiber spray-up molding apparatus had been designed and built. Polydicyclopentadiene (p-DCPD) is a crosslinking polymer with a very rigid network structure resulting excellent mechanical and corrosion resistant properties. In this research, the length of the glass fiber roving was cut such that it would be 100 times its critical length. Uniformity of the fiber volume distribution was examined by varying the spray height, glass fiber weight percentage and the fiber length. Mechanical properties were measured for each processing conditions. It was found that tensile strengths of the specimen fabricated with 50 mm glass fiber were higher over the shorter (25 mm) fiber only if sufficient spray height was achieved. It is definitely desirable to use long strands of chopped glass fibers for composite fabrication processes however; a careful manufacturing precaution is required since the effect of the adhesion force between long fibers from the fiber entanglement cannot be ignored.

An effect of boron nitride nanotubes (BNNTs) with a low concentration on the ablative resistance of the epoxy matrix was evaluated. A linear ablation rate of a 0.3 wt% BNNT/epoxy composite was nota...

The continuous glass fiber reinforced polylactic acid (PLA) prepreg was manufactured by direct melt impregnation. The mechanical and thermal properties of PLA prepreg were observed. The properties of PLA prepreg were compared with the neat PLA and the injection molded glass fiber/PLA composite. The PLA prepreg having a fiber volume fraction of 27.7 % shows well enhanced tensile strength of 331.1 MPa, flexural strength of 528.6 MPa, and flexural modulus of 24.0 GPa. The enhancement in the heat deflection temperature (HDT) and the crystallinity were also observed. The fracture interface was inspected by FE-SEM. The degree of impregnation as a function of pulling speed was measured. The degree of impregnation at the pulling speed of 5 m/min reached over 90 % in this research.

This paper investigates how people perceive the same material differently according to sex and nationality and what types of materials they prefer. We surveyed the sense of and preference for materials through questionnaires. The survey used five specimens made of zirconia, alumina, aluminum alloy, titanium alloy, and polycarbonate, and was conducted in four cities: Seoul and Ansan (Korea), Atlanta (USA), and Arusha (Tanzania). The survey consisted of three tests (a tactile test, a visual with tactile test, and an acoustic test). Except for the visual with the tactile test, the tests were conducted without any visual information. Using a statistical method, it was found that people feel the same materials differently depending on their sex and nationality. Furthermore, evaluation items which are correlated with material preferences such as roughness, coldness, familiarity, stiffness and color brightness levels were found, with these results showing that the evaluation items related to the preferences differ depending on the person’s sex and nationality.

The curing kinetics of endo-dicyclopentadiene (endo-DCPD) was analyzed using isothermal differential scanning calorimetry by experimentally acquiring kinetic parameters according to model fitting approaches. To investigate the effect of the decelerator, the curing kinetics of endo-DCPD with different amounts of decelerator solutions was also examined. The result of the developed model was in good agreement with the experimental data. The results showed that the decelerator had an effect on the delay of a reaction process and slowed down the curing process. The impact properties of glass fiber reinforced polydicyclopentadiene (p-DCPD) with different amounts of decelerator solutions were evaluated and compared with that of the glass fiber reinforced p-DCPD to investigate the effect of the decelerators. The impact energy was shown to decrease with increasing wt. % of decelerators from 0.5 wt % to 2.0 wt % with values from 10.75 to 15.89%, respectively.

In micro-injection molding, it is important to make each cavity filled uniformly. However, there are several factors that cause deviation in cavity filling. These factors include the mold temperature differential between runners and the diameter differential of gates or runners caused by mold manufacturing tolerances. In this study, we conducted numerical analysis to identify the major factors that cause cavity filling deviation and suggest a considerably robust design for microinjection mold to minimize the deviation. In the numerical simulation, we used thermophysical property values of EP-7000, one of the polycarbonate series polymers used for injection molding. The Cross-Arrhenius model was adopted with regard to the viscosity of the polymer. To model the specific heat and the thermal conductivity, we used the piecewise-linear method. Further, the volume of fluid method and the piecewise-linear interface scheme were used to visualize the polymer flow. Sixteen-cavity injection mold was modeled, and simulations were done for four different variations (the mold temperature, the runner diameter, the gate thickness, and a combination of the mold temperature and the runner diameter). Numerical analysis indicated that the case of mold temperature exhibited a difference of up to 28 % in instant cavity filling rate and the case of combination showed a difference of up to 33 %. We suggested designs employing convergent runner and resin reservoir to reduce deviation. As a result, the convergent runner design could reduce the instant cavity filling rate deviation by 20 %, while the resin reservoir design reduced the deviation by 18 %. The combination of these two could reduce the deviation by up to 22 %.

This study experimentally analyses the binding characteristics of analytes mixed in liquid samples flowing along a micro-channel to the receptor fixed on the wall of the micro-channel to provide design tools and data for a microfluidic-based biosensor. The binding or detection characteristics are analyzed experimentally by counting the number of analytes bound to the receptor, with sample analyte concentration, sample flow rate, and the position of the receptor along the micro-channel length as the main variables. A mathematical model is also proposed to predict the number of analytes transported and bound to the receptor based on a probability density function for Brownian motion. The coefficient in the mathematical model is obtained by using a dimensionless mathematical model and the experimental results. The coefficient remains valid for all different conditions of the sample analyte concentration, flow rate, and the position of the receptor, which implies the possibility of deriving a generalized model. Based on the mathematical model derived from mathematical and experimental analysis on the detection characteristics of the microfluidic-based biosensor depending on previously mentioned variables and the height of the micro-channel, this study suggests a design for a microfluidic-based biosensor by predicting the binding efficiency according to the channel height. The results show the binding efficiency increases as the flow rate decreases and as the receptor is placed closer to the sample-injecting inlet, but is unaffected by sample concentration.

This work reports the preparation of carbon fiber reinforced thermoplastic composites via the in situ anionic ring opening polymerization of &epsilon, caprolactam. Vacuum assisted resin transfer molding was used to fabricate polyamide-6/carbon fiber composites at different molding temperatures. As a result, the higher polymerization of &epsilon, caprolactam was observed with the condition at 140 &deg, C for satisfactory impregnation. Regarding molding temperature, the physical properties of polyamide-6/carbon fiber were observed that the bending and impact strengths at 140 &deg, C were higher than those to at other molding temperatures. The polymerization kinetics of polyamide-6 was analyzed using differential scanning calorimetry by experimentally acquiring kinetic parameters according to model fitting approaches. Polymerization and crystallization, which occur simultaneously throughout the whole process, were separated using Gaussian and Maxwell&ndash, Boltzmann distributions to study polymerization kinetics. The result of the developed model was in good agreement with the experimental data for the presented first order autocatalytic reaction model.

For the past six years, we have been benefiting from the discovery by Tsai and Melo (2014) that the trace of the plane stress stiffness matrix ( tr ( Q ) ) of an orthotropic composite is a fundamental and powerful scaling property of laminated composite materials. Algebraically, tr ( Q ) turns out to be a measure of the summation of the moduli of the material. It is, therefore, a material property. Additionally, since tr ( Q ) is an invariant of the stiffness tensor Q , independently of the coordinate system, the number of layers, layup sequence and loading condition (in-plane or flexural) in a laminate, if the material system remains the same, tr ( Q ) = tr ( A ∗ ) = tr ( D ∗ ) is still the same. Therefore, tr ( Q ) is the total stiffness that one can work with making it one of the most powerful and fundamental concepts discovered in the theory of composites recently. By reducing the number of variables, this concept shall simplify the design, analysis and optimization of composite laminates, thus enabling lighter, stronger and better parts. The reduced number of variables shall result in reducing the number and type of tests required for characterization of composite laminates, thus reducing bureaucratic certification burden. These effects shall enable a new era in the progress of composites in the future. For the above-mentioned reasons, it is proposed here to call this fundamental property, tr ( Q ) , as Tsai’s Modulus.

Recently new poly-dicyclopentadiene (p-DCPD) has increasing been used for composites in military, aerospace, and transportation applications due to its favorable impact properties. In this work, the cross-linking density of p-DCPD with different post curing conditions was indirectly measured by thermal analysis using differential scanning calorimetry (DSC), weight variation accompanying swelling and density. The effects of the post curing conditions on mechanical properties of p-DCPD and glass fiber (GF)/p-DCPD were determined via tensile, Izod impact, and flexural tests at ambient and low temperatures (-20 °C). Interfacial properties were evaluated by fragmentation and cyclic loading tests. The work of adhesion was determined via Static contact angle using four solvents measurements, to provide the information on the differences in the interfacial properties between GF and p-DCPD. The change of cross-linking density by post curing of p-DCPD affected the mechanical and interfacial properties of GF/p-DCPD composites.

Polyacrylonitrile (PAN) nanofiber and silica aerogel (SAG) laminated composites were prepared via electrospinning for thermal insulation. Conventional single nozzle and co-axial electrospinning wer...

Rigid polyurethane foam (PUF) is one of the outstanding insulation materials and has been widely used in freezers and cryogenic facilities. Among the various blowing agents used in the manufacturing PUF, water-blown PUF is attracting much attention as environmentally friendly PUF as prominent replacements for the environmentally hazardous CFCs and HCFCs due to their significant ozone depletion potential. We investigated the effective thermal conductivity of PUF blown with different amounts of water, on the basis of the heat transfer mechanisms in terms of thermal conduction of solids and gases and the thermal conductivity of radiation in the cells. A predictive model for the effective thermal conductivity of PUFs with different densities is presented. The predictive model was validated by comparing the predicted values with the experimentally measured ones. The result showed that the effective thermal conductivity increased from 0.023 to 0.027 W m−1 K−1 as the PUF density increased from 48 to 120 kg m−3: increased by 158% from 0.0034 to 0.0089 W m−1 K−1 for the thermal conductivity of solid PUF and decreased by 50% from 0.0037 to 0.0018 for the thermal conductivity of radiation.

Electrospinning, which produces nano/micro-fiber in a remarkably simple and fast manner, has been applied for numerous materials in various areas. In this study, the characteristics of micro-glass bead/PLA porous fiber composite were studied. The breath figure method was implemented to fabricate porous PLA fibers from PLA solution obtained by dissolving PLA in a solvent mixture (10:1 weight ratio) of dichloromethane (DCM) and N,N-dimethylacetamide (DMAc). The micro-beads (60 μm) were used to make more gaps between fibers and the specific surface area was measured and compared. Furthermore, the sound absorption and the insulation property of the samples were also measured. The specific surface area of samples increased from 1.45 to 4.39 m2/g with the addition of micro-glass beads and porous structure. The insulation property improved from 40 to 35 mW/m K with addition of micro-glass beads due to the formation of air layers.

In this study, functional particles such as piezoelectric (PZT) ceramic and shape memory alloy (SMA) particles have been incorporated in composite laminates to accelerate the loss of vibration energy. PZT ceramic particles and SMA particles are mixed with epoxy resin and rolled into a film shape before they are interleaved between prepreg plies for better distribution of the particles. Loss factor (tan δ) was measured with various particle loadings to verify the effectiveness of interleaving in the vibration damping of laminate specimens. It was observed that there existed an optimal content for maximizing the damping ability avoiding an aggregation of the particles. In addition, when PZT and SMA particles are applied simultaneously, PZT could enhance the vibration damping capability of SMA because PZT particles could generate thermal energy, and it would accelerate the phase change of the SMA particles. In this research, the effective way for enhancing the particle dispersion was suggested, and the particle loading could be controlled by finding an optimal content. Flexural moduli of the specimens were also measured, and they exhibited no change as the content of the particles increases. Therefore, dispersed particles used in this study increased the vibration damping capacity without reducing the mechanical properties.

In this work, micro- and nanocellular acrylonitrile-butadiene-styrene (ABS) foams were prepared by using sub- and supercritical CO2 as blowing agents. The sorption kinetics at 10 MPa was first measured. The sorption amount depended on the saturation temperature Arrheniusly. The diffusivities did not follow the Arrhenius relation. This relation was interpreted by a retrograde behavior of ABS/CO2 system. From the kinetics, ABS discs were saturated at 10 MPa at the temperatures from −20 °C to 40 °C, and foamed at the foaming temperature of 20 °C–80 °C. A network of closed cells with a diameter of 600–700 nm and nanopores with a diameter of 100 nm were observed in the foam obtained at low saturation temperatures and high foaming temperatures. The closed cell densities were in a range from 1.12 × 1012 − 9.87 × 1012 cells/cm3 and an experimental correlation based on the CNT model was used to fit the data.

The flexible syntactic foam with increasing attention as an eco-friendly building insulation material was manufactured via mold casting. The total porosity of the dried flexible syntactic foam had a very high value of 0.86 and the large vacant volumes in the microstructure were observed. The hollow glass spheres with the wide range of diameters were uniformly distributed inside the syntactic foam. It had low mechanical strength but showed toughness on a large compressive deformation. The thermal properties of the flexible syntactic foam were measured and compared with other insulation materials by dual probe method. The thermal conductivity and diffusivity of the flexible syntactic foam were 0.053 W/m·K and 0.097 mm2/s respectively. It also has low thermal effusivity thus it can be applied to a burn injury protection layer on high temperature surface.

Coalescence of droplets is a significant phenomenon, and it has been adapted to many applications such as raindrop formation, emulsion polymerization, ink-jet printing, coating, and multiphase flows. In this study, the morphological characteristics of two compressed adjacent droplets between two parallel plates were investigated to study the phenomenon of coalescence of droplets. By controlling the distance of the dispensed droplets, various results for coalescence of droplets were evaluated, especially, from the view of the minor axis, major axis, and meniscus liquid bridge of the coalesced droplet. Experimental results show that the length of the meniscus liquid bridge rapidly increases and then the rate of increase slows with time. The increase rate of the major and minor axes is largely influenced by the meniscus liquid bridge, which is mainly due to the curvature between the droplets. The numerical modeling of the coalescence of the two compressed droplets between two parallel plates was presented and simulation was conducted to realize the coalescence behavior. Comparison with numerical simulation showed that there was a good agreement with the experimental results.

In this study, syntactic foams composed of maximal hollow glass microparticles (HGMPs) volume fraction with improved thermal insulation performance and reasonable mechanical strength were fabricated through a new manufacturing approach. Use of low fraction binder materials diluted in solvent enabled minimal contacts among the HGMPs assisted by a natural capillary trend, as confirmed by in situ and ex situ optical and electron microscope imaging. Composite level samples of practical thickness, fabricated by a layer-by-layer coating approach, exhibited enhanced thermal insulation performance, as characterized by infrared thermal imaging and quantitative thermal conductivity measurement. Via microscope inspection under tensile loading, a favorable particles–binder bonding trend was inspected in terms of mechanical strength. The fabricated composite materials have potential for building insulation applications because of their relatively simple and scalable manufacturing nature, minimal use of binder materials, and mechanical strength to maintain and tailor shape. Further studies are necessary to understand mechanical and thermal properties of the composites, and key fabrication mechanisms involved with self-assembly under complex multi-components and phases.

In this study, the liquid–vapor mixture model was used for a numerical study of natural convective flow in a cryogenic tank with a capacity of 4.9 m3 under various conditions of heat flux and filling level to understand the early stages of convective flow phenomena and the consequent thermal stratification of cryogenic liquid. Two cryogens—liquefied natural gas (LNG) and liquefied nitrogen (LN2)—were compared to observe their effects. LN2 exhibited faster vaporization owing to its lower heat of vaporization. It was observed that higher heat flux and lower filling level led to faster vaporization and relatively vigorous heat transfer, showing early thermal stratification.

Composites using dicyclopentadiene (DCPD) as a matrix have gained significant popularity owing to their excellent impact and chemical corrosion resistance. In the present study, experiments addressing the impact behavior of glass-fiber-reinforced DCPD were conducted to quantitatively evaluate its impact properties. The glass-fiber-reinforced polydicyclopentadiene composite utilized in impact tests was manufactured using structural reaction injection molding (S-RIM) because of its fast curing characteristics and low viscosity. The impact properties of the glass-fiber-reinforced DCPD (GF/DCPD) were quantitatively evaluated by varying its fiber content and decelerator solution. The impact properties of neat DCPD and GF/DCPD composites were examined with different amounts of decelerator solution under various temperatures from room temperature to cryogenic temperature to observe the ductile-to-brittle transition temperature (DBTT). With an increase in the fiber weight fraction of the GF/DCPD composite, the effect of the DBTT significantly decreased. However, the decreasing rate retarded as the weight fraction of the GF increased. The decreased DBTT with the addition of GF in the GF/DCPD can be attributed to the differences in the thermal expansion ratio and the interfacial force between neat DCPD and the fiber. A fractograph analysis demonstrates that the effect of the brittle (smooth) surface resulted in a lower impact absorbed energy when the temperature decreased, along with the increased amount of the decelerator.

The effects of major process parameters on particle filtration and distribution were investigated by using newly developed microscopic methodology using an electron probe micro-analyzer and numerical simulation. The mapping results indicated that well-dispersed particles were distributed uniformly in the inter-tow and intra-tow regions. Agglomerates were likely to be filtered at the boundary or inside of the fiber bundle. The results of quantitative analyses showed particle concentrations in the inter-tow region to be uniform throughout the composite part, whereas the intra-tow concentrations varied according to particle size and fiber orientation. The poor dispersion state of the CNT-Ag particles resulted in quite irregular distributions. A high volume fraction of the fiber preform resulted in a lower particle concentration inside the fiber tow. Numerical analysis of the filtration of large clusters of particles indicated that filtration occurred in the initial stage of the injection process at the tow boundaries.

In this investigation, we studied the effect of the cavity air pressure on the replication of micro-patterns in injection molding. When pressure is applied to the cavity air, the pressure at the flow front is also increased and thus the overall pressure gradient in the polymer melt is lowered. Therefore, the melt flow in the cavity becomes slower providing more time for the polymer melt to fill the patterns on the cavity surface resulting in the improvement of replication of the microscopic pattern. We carried out experiments for molds with a macroscopic pattern (ribs) and a microscopic pattern on the surface. In order to evaluate the quality of replication, we measured the filling heights of patterns with different ratio of the cavity air pressure to the injection pressure. The results showed that the application of cavity pressure helps the replication of patterns both for macroscopic and microscopic scales.

In this study, degradation behavior of polylactic acid (PLA) composite reinforced with different types of particles (titanium dioxide, multi-walled carbon nanotubes, surface-treated multi-walled carbon nanotubes, and graphene nanoplatelets) were investigated. Samples were prepared by extrusion and injection molding. Hydrolytic degradation was induced by immersing the specimen in a sodium hydroxide solution. Particles can affect the crystallization kinetics of PLA matrix which may affect the degradation behavior. In order to examine the crystallization kinetics and crystallinity of PLA matrix, differential scanning calorimetry and X-ray diffraction measurements were employed. Annealing was done for different durations of time in order to control the crystallinity of the matrix. The results show that the crystallization rate was remarkably increased due to the addition of particles and that there was an optimal concentration of particles. The degradation rate of most of the PLA composites was faster than that of neat PLA, indicating that the interface between the particle and the PLA matrix was not perfect. Meanwhile, the degradation rate of PLA reinforced with multi-walled carbon nanotubes became slower due to increased crystallinity.

In this paper, we proposed a construction plan of cyber training scheme for enhancing the quality and capability of military cyber warriors needed to cyber warfare. Most of cyber training is conducted in the country have been working to prior notice way based on a training scenario. This being so, it is closer to proficiency training to acquaint and follow a training scenario rather than a training program for enhancing the capability of cyber warriors. And systematic training process according to the capability level of cyber expert does not established. In particular, the education and training system for cyber warriors specializing in cyber warfare is not entirely satisfactory. Cyber warriors should have such knowledge as military strategy and operations, cyber(IT) environment background, and cyber attack&defense technologies to perform cyber warfare. In order to train cyber warriors to equip these capabilities, professional and specialized training system is required. So, we present a cyber warfare training scheme according to the level of capabilities required by the rank and duties of military cyber warriors.

As the large liquefied natural gas (LNG) carrier has emerged as an important LNG transportation, rigorous safety analysis of the carrier is required to achieve reliable technological solutions for safely transporting LNG. The present study uses numerical simulation (conjugate thermal analysis) to investigate LNG leakage and the consequent temperature change of the hull׳s steel plate in a LNG cargo containment system (CCS). To validate the numerical approach used in the study, experimental investigation on the temperature behavior of the hull׳s plate was conducted. The experimentally determined ductile-to-brittle transition temperature (DBTT) was used as the index of critical temperature for the hull׳s plate. A numerical simulation was used to estimate the behavior of cryogenic liquid in a porous structure in an LNG CCS and the resulting temperature change of the hull׳s plate due to LNG leakage under any filling conditions (various inlet pressures of leaking LNG and defect sizes). According to the numerical study, the thermal safety of the hull׳s plate is guaranteed in case where the LNG leakage hole is 2 mm in diameter. The critical leakage hole size where temperature of hull׳s plate did not reach a DBTT lies between 2 mm and 5 mm under the leakage conditions.

In recent years, the demand for composite materials in various industries such as aerospace, defense, and automotive industries has increased significantly. Furthermore, the mechanical properties of carbon fiber-reinforced plastic (CFRP) composites have been improved significantly. However, the out-of-plane (thickness direction) mechanical properties of CFRP laminates are considerably inferior to their in-plane mechanical properties. Owing to their unique properties, carbon nanotubes (CNTs) have been used to improve the mechanical properties of CFRP composites. However, it is challenging to disperse high concentrations of CNTs in the polymer resin matrices of such composites. In this study, a high concentration of CNTs was incorporated in CFRP laminates in the form of CNT/epoxy films by using ultrasonication and three-roll milling. Furthermore, unidirectional and plain woven prepregs were used for reinforcement. The mode II interlaminar fracture toughnesses of the CNT/epoxy film-interleaved CFRP composites with different CNT concentrations were measured by carrying out their end-notched flexure (ENF) tests. Optical micrographs were obtained to observe the microstructures of the specimens with different CNT loadings. The fracture surfaces obtained after the ENF tests were examined using a scanning electron microscope to investigate the toughening mechanism of the composites.

Fluid flow related to heat transfer with a change in phase is an important phenomenon because many industrial processes rely on them for material processing and energy transfer. Examining fluid flow associated with heat transfer with a change in phase involves multiphase flow analysis, which can be utilized in various applications. In particular, studying the flow phenomena of a cryogenic liquid subjected to evaporation can help better understand cryogenic liquid behavior in a porous structure. In present study, the flow phenomena of a cryogenic liquid in a porous structure, glass wool, were examined. We conducted an experimental investigation of the behavior of a cryogenic liquid in porous media with various densities in order to understand how the cryogenic liquid behaves in a porous structure. The present study examined the thermophysical properties of glass wool media with different bulk densities and investigated its permeability under different injection pressures. The experimentally determined thermophysical properties and permeability were used to explain the experimental results. In two distinct experiments, temperature and pressure were measured to find the phase state of the flow and the tendency of propagation of the liquid-saturated region in glass wool media with different bulk densities. The results revealed that the nonlinearity of the pressure distribution over distance increased as the bulk density of the glass wool increased, and the rate at which the pressure gradient increase became conspicuously greater with accretion in injection pressure. Numerical simulation was conducted to further understand a cryogenic liquid’s flow behavior in porous media, and the simulation results were compared with the experimental results. The numerical simulation results were in good agreement with the experimental results.

The ablation properties and thermal conductivity of carbon nanotube (CNT) and carbon fiber (CF)/phenolic composites were evaluated for different filler types and structures. It was found that the mechanical and thermal properties of phenolic-polymer matrix composites were improved significantly by the addition of carbon materials as reinforcement. The concentrations of CF and CNT reinforcing materials used in this study were 30 vol% and 0.5 wt%, respectively. The thermal conductivity and thermal diffusion of the different composites were observed during ablation testing, using an oxygen–kerosene (1:1) flame torch. The thermal conductivity of CF mat/phenolic composites was higher than that of random CF/phenolic composites. Both CF mat and CNT/phenolic composites exhibited much better thermal conductivity and ablation properties than did neat phenolic resin. The more conductive carbon materials significantly enhanced the heat conduction and dissipation from the flame location, thereby minimizing local thermal damage.

Being lightweight materials with good mechanical and thermal properties, hollow glass micro-particles (HGMPs) have been widely studied for multiple applications. In this study, it is shown that by using reduced binder fraction diluted in solvent, enables minimal contacts among the HGMPs assisted by a natural capillary trend, as confirmed by optical and electron microscope imaging. Such material architecture fabricated in a composite level proves to have enhanced thermal insulation performance through quantitative thermal conductivity measurement. Mechanical strength has also been evaluated in terms of particle-binder bonding by tensile test via in-situ microscope inspection. Effect of laser treatment was examined for further improvement of thermal and mechanical properties by selective binder removal and efficient redistribution of remaining binder components. The fabricated composite materials have potential applications to building insulation materials for their scalable manufacturing nature, improved thermal insulation performance and reasonable mechanical strength. Further studies are needed to understand mechanical and thermal properties of the resulting composites, and key fabrication mechanisms involved with laser treatment of complex multi-component and multi-phase systems.

We investigate the unsaturated resin flow behavior in a dual scale porosity preform by observing the pressure distribution and the void content. The experimental data show that the pressure profile in the unsaturated flow is nonlinear with positive curvature whereas that in the saturated flow is linear as expected from the classical Darcy's law. To address this issue, the governing equation for mass conservation is modified by introducing a mass sink term. Eventually, it has been found that the discrepancy between the unsaturated and saturated permeability values comes from a misinterpretation of the pressure gradient at the flow front in the unsaturated permeability measurement method and the permeability for a given preform is a unique value regardless of measurement method or flow condition. Based on this investigation, the ratio of unsaturated permeability to saturated permeability is represented as a dimensionless number in terms of void content. © The Author(s) 2016.

The aims of this study were to fabricate lightweight composites having isotropic electrical and thermal conductivities. The composites consist of expanded polypropylene (EPP) and chopped carbon fib...

In this study, we investigated the use of composite patches to repair aluminum alloy double-lap joints. The carbon composite patches were cured using induction curing or oven curing. Joints were repaired using precured or cocured composite patches. The bond strengths of the different joints were compared. We also investigated whether the incorporation of carbon nanotubes (CNTs) in the adhesive bondline affected bond strength. We found that the induction-cured samples exhibited bond strengths similar to those of the corresponding oven-cured samples; this was true for both the baseline and the CNT-reinforced samples. Further, the samples processed using cocured patches exhibited higher bond strengths than did the corresponding samples processed using precured patches. In the case of both the precured and the cocured patch samples, the dispersion of 0.5 wt% CNTs in the adhesive bondline increased the bond strength slightly. The effect of the two different types of patches placed on top of the aluminum substr...

Ablative materials are used as a thermal protection system for objects exposed to extreme friction and ultrahigh temperature. The ablation resistance of epoxy resin reinforced with multi-walled carbon nanotubes (MWCNTs) at low concentration was investigated. The ablation resistance improved with increasing MWCNT content. The linear ablation rate of 0.5 wt% MWCNT was 30.7% less than that of neat epoxy. On the ablated surface, curved cylinder structures with superior strength to the surrounding matrix were formed around MWCNTs which acted as nucleation sites. X-ray diffraction and Raman spectroscopy revealed the formation of near-graphite structures around MWCNTs in the non-graphitizable epoxy matrix. In conclusion, MWCNTs at low concentration could facilitate the formation of near-graphitic structures in quite large region of epoxy matrix, so dramatically enhanced ablation resistance.

Highly ablation resistant carbon nanotube (CNT)-phenolic composites were fabricated by the addition oflow concentrations of CNT nanofiller. Tensile and compressive properties as well as ablative resistance weresignificantly improved by the addition of only 0.1 and 0.3 wt% of uniformly dispersed CNTs. An oxygen-kerosene-flame torch and a field emission scanning electron microscope (FE-SEM) were used to evaluate the ablative propertiesand microstructures of these CNT-phenolic composites. Thermal gravimetric analysis (TGA) revealed that the ablationrate was lower for the 0.3 wt% CNT-phenolic composites than for neat phenolic or the composite with 0.1 wt% CNT.Ablative mechanisms for all three materials were investigated using this TGA in conjunction with microstructuralstudies using a FE-SEM. The microstructural studies revealed that CNT acted as an ablation resistant phase at hightemperatures, and that the uniformity of dispersion of the CNT played an important role in this resistance to ablation.초록

A novel process of atmospheric pressure plasma treatment was performed, on powdered carbon nanotube (CNT) in water, to modify reinforcing effects and interfacial adhesion in carbon fiber reinforced CNT-phenolic composites. The change in chemical functional groups, as result of the plasma-treatment, was analyzed using Fourier transform infrared (FT-IR) spectroscopy. A significant enhancement in the wettability of plasma-treated CNT was also confirmed by static contact angle measurements. The advancing contact angle indicated a change in the surface from hydrophobic to hydrophilic. The interfacial adhesion between the carbon fibers and the plasma-treated CNT-phenolic matrix also improved, as evidenced by an increase in the apparent modulus. Due to the brittle nature of the phenolic matrix, dual matrix composites (DMC) were used in a modified fragmentation test. The different microfailure modes (phenolic matrix cracking and carbon fiber breaking) were investigated by acoustic emission and electrical resistance measurements.

The continuous glass fiber reinforced poly-lactic acid (PLA) composite was manufactured by direct meltimpregnation. The mechanical and thermal properties of continuous glass fiber reinforced PLA composite wereobserved. Measured properties were compared with the reference values of neat PLA and the injection molded glassfiber/ PLA composite. The continuous glass fiber reinforced PLA composite having a fiber volume fraction of 27.7%shows enhanced tensile strength of 331.1 MPa, flexural strength of 528.6 MPa, and flexural modulus of 24.0 GPa. Theenhanced heat deflection temperature (HDT) and the increased cystallinity were also observed. The degree ofimpregnation as a function of pulling speed was also assessed. The degree of impregnation at the pulling speed of5 m/min was over 90% in this research.초록 : 본연구에서는연속 유리섬유강화폴리유산 복합재료를 직접함침방법을 이용하여제조하였고, 이의 기계적 열적 물성이 고찰되었다. 프리프레그의 물성은 기존의 알려진 폴리유산의 물성과 사출 성형으로 제조된 유리섬유 강화 폴리유산 복합소재와 비교 평가되었으며, 섬유체적분율 27.7% 를 갖는 연속 유리섬유 강화 폴리유산 복합재료의 인장응력, 굽힘응력, 굴곡탄성율은 각각 331.1 MPa, 528.6 MPa, 24.0 GPa의 향상된 값을 보였다. 또한 향상된 열변형 온도와 결정화도가 확인되었다. 생산속도에 따른 함침도가 고찰되었고, 그 결과 본 연구에 사용된 공정조건에서는 분당 5 m의 섬유당김속도에서 함침도 90% 이상의 연속 유리섬유 강화 폴리유산 복합재료를 제조가능하였다.

There has been an increase in the use of fiber-reinforced composite materials in many areas. In particular, glass-fiber-reinforced composites have gained in popularity owing to their low cost, high-strength properties, durability, ease of repair, and being simple to form. This paper analyzes the buckling load for the glass-fiber-reinforced plywood specifically used for the liquid natural gas cargo tank and carriers, especially the No 96 cargo containment system insulation box. The buckling load of the plywood reinforced with glass fiber composite on both outer surfaces was estimated with various composite thicknesses and compared with the buckling load of unreinforced plywood. The buckling load was also evaluated at various temperatures to verify the temperature dependence of the buckling load. A much higher buckling load for the glass fiber/epoxy-reinforced plywood was obtained as the number of glass fiber/epoxy prepreg composite was increased. However, the rate of increase in the buckling load decreased as the temperature decreased and as the number of glass fiber/epoxy prepreg composite increased.

Numerous filler particles are being developed and applied to improve the properties of conventional composite materials or to develop composite materials with additional functionalities. When filler particles are added to the polymer matrix of a fiber-reinforced composite material, the particles dispersed in the polymer resin can be filtered between fiber strands during the manufacturing process, which leads to a nonuniform particle distribution and material defects. Therefore, understanding and controlling such filtration phenomena has become a critical issue. In the present study, a new microscopic methodology for measuring the distribution of filler particles in fully cured composite parts using an electron probe microanalyzer (EPMA) is proposed. The distributions of spherical titanium dioxide particles and carbon nanotubes conjugated with silver nanoparticles as tracers were visualized by elemental mapping analysis. Furthermore, the concentrations were separately measured in the intratow and intertow regions by quantitative analysis.