• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.904-914
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• 2004

The fiber reinforced composite material is widely used in the multi-industrial field because of their high specific modulus and specific strength. It has two main merits which are to cut down energy by reducing weight and to prevent explosive damage proceeding to the sudden bursting which is generated by the pressure leakage condition. Therefore, Pressure vessels using this composite material can be applied in the field such as defence industry and aerospace industry. In this paper, for nonlinear finite element analysis of E-glass/epoxy filament winding of composite vessel subjected to internal pressure, the standard interpretation model is developed by using the ANSYS with AutoLISP and ANSYS APDL languages, general commercial software, which is verified as useful characteristic of the solution. Among the modules of the system, both the process planning module for carrying out the process planning of filament wound composite pressure vessel and the autofrettage process module for obtaining higher residual stress will minimize trial and error and reduce the period for developing new products. The system can serve as a valuable system for experts and as a dependable training aid for beginners.

• Polymer(Korea)
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• v.30 no.3
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• pp.259-265
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• 2006

Small intestinal submucosa (SIS) consists of some growth factors which can stimulate cell activity, and PVA has been widely utilized in the area of wound dressing as hydrogel which is easy to be removed from wounds. In this study, native SIS sheets were coated with PVA by immersing them into 2, 4, and 10 wt% of PVA solution and then lyophilized on two type of molds to endow the prepared wound dressing with easy removal property from wounds. The mechanical properties were examined through tensile test. Moreover, enzymatic degradation, water uptake, and in vitro test were carried out to characterize the prepared SIS sheets. The tensile strength of the SIS sheets coated with PVA (PVA-SIS) were decreased, whereas the elongation were increased. Degradation ratio of the PVA-SIS sheets was decreased compare to native SIS. Water uptake ability was improved at 2 and 4 wt% of PVA. The degree of fibroblast attachment was lower than the native SIS sheets. In conclusion, this study suggests that the PVA coated SIS sheets have a potential for the applications of wound dressing and biodegradable injectable materials.

• Polymer(Korea)
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• v.25 no.5
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• pp.728-735
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• 2001

In this study, hydrogels from mixtures of chitosan/poly(vinyl alcohol) (PVA) and chitosan/poly(N-vinylpyrrolidone) (PVP) were prepared by ${\gamma}$-ray irradiation, and the mechanical properties such as gelation, water absorptivity and gel strength were examined to evaluate the applicability of these for wound dressing. The PVA : chitosan and PVP : chitosan ratio were in the range of 97:3 ~ 90:10, and the solid concentration of PVA/chitosan and PVP/chitosan solution were 15 wt%. Gamma irradiation with doses of 25, 35, 50, 60 and 70 kGy, was exposed to mixtures of PVA/chitosan and PVP/chitosan to evaluate the effect of irradiation dose. Gel content and gel strength increased as chitosan concentrations in PVA/chitosan and PVP/chitosan decreased, and as irradiation dose increased. Swelling degree increased as chitosan concentrations in PVP/chitosan and PVA/chitosan increased, and as irradiation dose decreased.

• Journal of Biomedical Engineering Research
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• v.8 no.1
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• pp.87-92
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• 1987

In order to evaluate the artificial skin for burn would covering materials, copoly(N. carbobenzoxy-L-Iysine-L-leucine)s were prepared by Ipolymerization of N - carbobenzoxy-L- I sine anhydride and L-leucine anhydride in homogeneous solvents using triethylamine as an initiator. The synthetic polypeptides and the oxter type polyurethane(PV)of medical grade were used as the sheet type membranes were prepared ; monolayer membrances were composed of only the polypeptides, bilayer membranes and blend membranes were controlled by composition of the polypeptides and PU. Test of the swelling degree, mechanical tensile strength, elongation, oxygen permeability, water-vapor loss and In vitro degradation treated by pretense TV of samples of artificial skin were measured by adequate methods so as to mechanical, physincal characterization and biodegradation. As a result, all the values of samples were found to be similar to desired value of skin which was nature. The Artificial skin based on polypeptides can be considered as ideal burn wound covering materials.

• Composites Research
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• v.34 no.3
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• pp.174-179
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• 2021

Currently, fluid transfer steel pipes take a lot of time and expense to maintain all facilities due to new construction and painting or corrosion and aging. Therefore, this study was conducted for designing a CFRP pipe structure with high corrosion resistance and chemical resistance as a substitute for steel pipes. The helical/hoop pattern was cross-laminated to improve durability, and HNT was added to suppress the moisture absorption phenomenon of the epoxy. The HNT/CFRP pipe was manufactured by a filament winding process, and performed a mechanical property test, and a moisture absorption test in distilled water at 70℃. As a result, the highest bending strength was obtained when the hoop pattern was laminated with a thickness equivalent to 0.6% of the pipe. The 0.5 wt% HNT specimen had the highest moisture absorption resistance. Also, the delamination phenomenon at the interlayer interface was delayed, resulting in the lowest strength reduction rate.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.931-937
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• 2018

Sutures are used not only for wound closure but also for oriental medicine field, beauty and even for plastic surgery. Especially, it is popular in the field of cosmetic surgery. In this paper, we produced sutures using PCL and PLLA with better strength than PDO sutures, which was widely used in the past. To learn about the mechanical characteristics of the PCL and PLLA sutures, the contraction change, tensile strength, and elongation were measured. And SEM was also analyzed for diameter and surface. The contraction change Ratio of sutures are stabilized after a certain period of time regardless of temperature. Also, it can be seen that the higher the temperature, the higher the contraction increase rate. And the rate change of mechanical properties is different according to the temperature before and after the glass temperature. Also the higher the temperature, the faster the molecular motion and the lower the tensile strength. The diameter of the PLLA and PCL sutures is opposite to the contraction change ratio. And it is considered that the sterilization temperature of PLLA sutures is best to set at $45^{\circ}C$ and the sterilization temperature of PCL sutures is best to set at $35^{\circ}C$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.9
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• pp.25-32
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• 2006

In this study, the characteristics of filament wound composite/aluminum ring specimens were investigated at cryogenic temperature. The ring specimens were manufactured using carbon fibre and Type B epoxy resin which had been developed for cryogenic use. As a result of measuring thermal strains at -150℃, it was found that compressive thermal stress was induced in composite part on the contrary, tensile thermal stress in aluminum part which was about 32% of yield stress and in turn, caused aluminum to be yielded at lower load level. In addition, Thermal strains which resulted from finite element analysis showed good agreement with those of the experiment. After 6 mechanical loading cycles had been applied to the ring specimen at -150℃, tensile tests were performed at -150℃ using a split disk fixture. As a result, it was shown that composite strength in a liner-composite tank structure which is for the use of cryogenic propellant tank would be decreased by auto-frettage pressure which is applied to it.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.4
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• pp.303-310
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• 2017

Pressure retarded osmosis(PRO) has attracted much attention as potential technology to reduce the overall energy consumption for reverse osmosis(RO) desalination. The RO/PRO hybrid process is considered as the most logical next step for future desalination. The PRO process aims to harness the osmotic energy difference of two aqueous solutions separated by a semipermeable membrane. By using the concentrated water(RO brine) discharged from existing RO plants, the PRO process can effectively exploit a greater salinity gradient to reduce the energy cost of processing concentrated water. However, in order to use RO brine as the draw solution, PRO membrane must have high water flux and enough mechanical strength to withstand the high operational pressure. This study investigates the development of a thin film composite PRO membrane and spiral wound module for high power density. Also, the influence of membrane backing layer on the overall power density was studied using the characteristic factors of PRO membranes. Finally, the performance test of an 8-inch spiral wound module was carried out under various operating conditions(i.e. hydraulic pressure, flow rate, temperature). As the flow rate and temperature increased under the same hydraulic pressure, the PRO performance increased due to the growth of water permeability coefficient and osmotic pressure. For a high performance PRO system, in order to optimize the operating conditions, it is highly recommended that the flow pressure be minimized while the flow rate is maintained at a high level.

• Polymer(Korea)
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• v.37 no.6
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• pp.717-721
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• 2013

Biomaterials like silk fibroin (SF) and poly(vinyl alcohol) (PVA) have received increasing attention in biomedical applications because of their attractive properties such as hydrophobicity and biocompatibility. In this study, efficient systems consisting of interpenetrating SF/PVA hydrogels were prepared as potential candidate for wound dressing applications. A simple approach consisting of sonication and a freezing-thawing technique was adopted to fabricate the hydrogels. Different blend ratios consisting of SF (100, 75, 50, 25 and 0%) with respect to the weight of PVA were prepared. The produced hydrogels were characterized for physico-chemical investigations using various states of techniques like; FE-SEM, TGA, FTIR and tensile strength. The addition of PVA to SF was proved to be beneficial in terms of reducing the pore size and swelling ratio of hydrogels. The mechanical property of SF had been increased by addition of PVA. These results show that SF/PVA hydrogels may serve as potential candidates for wound dressing application.

• Transactions of the KSME C: Technology and Education
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• v.1 no.2
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• pp.167-177
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• 2013

The use of mechanical anastomosis coupler instead of sutures has been increasing in microvascular anastomosis surgery. However, non-biodegradable anastomosis coupler has problems such as not only inflammatory reaction but also remaining permanently in operation wound. Therefore, we fabricated biodegradable anastomosis coupler using injection molding process to overcome the limitation of non-biodegradable anastomosis coupler. In various injection molding process conditions, the shrinkage was calculated with different cylinder temperatures and injection molding pressures and anastomotic strength was measured. As a result, changes in shrinkage hole part larger than the pin part. In addition, the shrinkage in the cylinder at higher temperatures increase. However, the higher the injection pressure, shrinkage tends to decrease, respectively. In-vitro degradation behavior of PCL anastomotic coupler evaluated for 12 weeks, water uptake was increased and molecular weight was accompanied by a reduction in mass of the biological degradation and reduction of anastomotic strength was confirmed. However, decreased levels of anastomotic strength enough to exceed the requirements of preclinical surgery, PCL microvascular anastomosis coupler suitable candidate materials that could identify.