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

• Composites Research
• /
• v.33 no.5
• /
• pp.275-281
• /
• 2020

The mechanical property related to lap shear strength of the joint structure between carbon fiber reinforced polymer (CFRP) composite and metal (Ni-Cr Alloy) under varying environmental conditions (temperature and humidity) was studied in order to apply to the aircraft fan blade. Room temperature dry (RTD), elevated temperature wet (ETW), and cold temperature dry (CTD) environmental conditions were chosen for investigation based on the flight conditions of aircraft. Lap shear strength tests were conducted according to ASTM Standard D3528 to evaluate the shear strength. The microstructure characteristic of failure zone was analyzed by SEM images to check the adhesive shear strength with the three environmental conditions. In comparison with shear strength for the RTD condition, the shear strength in the ETW condition was reduced by 72.8% while those for the CTD condition increased by 56.5%. The moisture absorption and high temperature in ETW condition strongly had an affect on mechanical property of adhesive, while cold temperature could enhance the adhesive shear strength due to the higher brittleness.

• Journal of the Korean Wood Science and Technology
• /
• v.10 no.2
• /
• pp.3-11
• /
• 1982

In order to investigate the annual mean equilibrium moisture content(EMC), the equilibrium moisture content investigated were the desorbed and adsorbed equilibrium moisture content with two end-matched samples for red pine (Pinus densiflora S. et Z.), Douglas fir (Pseadotsuga menziesii Franco), oak (Quercus mongolica Fischer) and red lauan (Shorea spp.) in instrument screen at forest experiment station located in Seoul, Chuncheon, Daejeon, Kyungju, Jinju and Gwangju area for four years (1970. 1 - 1973. 12). The results summarized were as follows. 1. The annual mean desorbed equilibrium moisture content of red pine, Douglar fir, oak and red lauan were 14.8, 13.7, 14.0 and 14.2 percent respectively and higher than the annual mean adsorbed equilibrium moisture content of those species. 2. The annual mean desorbed - and adsorbed equilibrium moisture content in central areas (Seoul, Chuncheon, Daejeon) were higher than those in southern areas (Kyungju, Jinju, Gwangju). 3. On the whole, the monthly mean desorbed - and adsorbed equilibrium moisture content were lowest in April and highest in August though difference of month in areas. 4. Average and range of annual national equilibrium moisture content was 12.3 ~ 14.2 ~ 15.7 percent for desorbed equilibrium moisture content and 11.3 ~ 13.2 ~ 14.7 percent for adsorbed equilibrium moisture content and 12.0 ~ 14.1 ~ 16.4 percent for calculated equilibrium moisture content based on tempera ture and humidity.

• Journal of the Korean Wood Science and Technology
• /
• v.10 no.3
• /
• pp.109-117
• /
• 1982

In order to investigate the annual mean equilibrium moisture content (EMC), the equilibrium moisture content investigated were the desorbed - and adsorbed equilibrium moisture content with two end-matched samples for red pine (Pinus densiflora S. et Z.), Douglas fir (Pseadotsuga menziesii Franco), oak (Quercus mongolica Fischer) and red lauan (Shorea spp.) in instrument screen at forest experiment station located in Seoul, Chuncheon, Daejeon, Kyungju, Jinju and Gwangju area for four years (1970. 1 - 1973. 12). The results summarized were as follows. 1. The annual mean desorbed equilibrium moisture content of red pine, Douglar fir, oak and red lauan were 14.8, 13.7, 14.0 and 14.2 percent respectively and higher than the annual mean adsorbed equilibrium moisture content of those species. 2. The annual mean desorbed - and adsorbed equilibrium moisture content in central areas (Seoul, Chuncheon, Daejeon) were higher than those in southern areas (Kyungju, Jinju, Gwangju). 3. On the whole, the monthly mean desorbed - and adsorbed equilibrium moisture content were lowest in April and highest in August though difference of month in areas. 4. Average and range of annual national equilibrium moisture content was 12.3 ~ 14.2 ~ 15.7 percent for desorbed equilibrium moisture content and 11.3 ~ 13.2 ~ 14.7 percent for adsorbed equilibrium moisture content and 12.0 ~ 14.1 ~ 16.4 percent for calculated equilibrium moisture content based on tempera.

• Food Science and Preservation
• /
• v.10 no.3
• /
• pp.297-301
• /
• 2003

The hardness of corrugated packaging box decreased during storage period because of high humidity. Therefore, the strength-decreasing factor of corrugated packaging box had to be investigated to determine the compression strength of the corrugated packaging box. This study was conducted to define the characteristics of moisture absorption as well as compression strength of corrugated fiberboard. (1) The moisture content of the corrugated fiberboard was rarely influenced by the kinds of raw materials and water repellent. However, the moisture adsorption of the corrugated fiberboard was shown to be clearly affected by air temperature changes. (2) The moisture content of the corrugated fiberboard was significantly affected by relative humidity. The moisture adsorption of corrugated fiberboard was also greatly influenced by composition of raw materials rather than water repellent. The results indicated that the improvement of raw materials was more effective than the increase of water repellent of corrugated fiberboard to reduce the moisture adsorption of the corrugated fiberboard. (3) The vertical compression strength was significantly decreased with increasing relative humidity. The reduction rate of vertical compression strength was not charged with the increase of relative humidity, which was regardless of kinds of corrugated fiberboard. (4) For improving the strength of the corrugated packaging box, new technique should be found to develop better quality of raw materials. Moreover, the physical construction of corrugated packaging box should be clearly understood because the corrugated packaging box for the agricultural products was usually used for the circumstances of high humidity and low air temperature

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.2034-2035
• /
• 2008

본 논문은 RVM(Return Voltage measurement)을 이용하여 식물유와 광유에 따른 절연지의 수분 흡습성에 관한 특성을 비교하였다. 시험 절연재료로써 절연유는 각각 식물유(Bio Trans 1000,Cargill사)와 광유(제1종 2호, 동남석유(주))를 사용하였고, 절연지는 셀룰로오스계 크래프트 절연지를 사용하였다. 각 조건에서 IEEE/ANSI Standard C59.91-1981의 기대수명 곡선에서 $55^{\circ}C$ 절연을 기준으로하여 가속 열열화 시험을 수행한 후, $15^{\circ}C$씩 온도를 변화시켜 RVM 측정을 하였다.

• Korean Journal of Materials Research
• /
• v.7 no.5
• /
• pp.434-443
• /
• 1997

유리섬유와 에폭시 수지와의 계면전단강도에 미치는 수분흡수, 섬유직경 및 섬유의표면상태 등의 영향을 검토하기 위해서 two fiber fragmentation 시험법을 사용하였다. 그리고 유리섬유/에폭시 수지의 일방향 복합재료에서 수분흡수가 복합재료의 기계적 성질에 미치는 영향에 대해서도 검토하였다. 그 결과, two fiber fragmentation시험에서 계면전단강도는 수분흡수량 및 섬유직경이 클수록 작게 나타났으며, sizing한 것이 desizing한 것보다 크게 나타났다. 또 수분흡습에 의해 감소되었던 계면전단강도는 건조에 의해서 처음의 값의 약 50-60%까지 회복됨을 나타내었다. 그리고 일방향 복합재료의 인장강도는 수분흡수량이 증가함에 따라 현저히 감소함을 보였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.5
• /
• pp.523-528
• /
• 2012

A bendable electronic module is developed for a mobile application by using a low-cost roll-to-roll manufacturing process. In the module, a thin silicon chip is embedded in a polymer-based encapsulating adhesive between flexible copper clad polyimide layers. A set of tests are conducted for the purpose of qualification: thermal shock, high temperature storage, and autoclave tests. During the autoclave test, delamination occurs at many places within the module layers. To investigate the failure mechanism, moisture diffusion analysis is conducted for the interior of the module under the autoclave test condition. For the analysis, the hygroscopic characteristics of the encapsulating materials are experimentally determined. Analysis results indicate the moisture saturation process in the interior of the module under the autoclave test condition.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.10
• /
• pp.6816-6822
• /
• 2015

In this study, silica aerogel-glass wool composites were developed for improvement of thermal conductivity and overcoming the water adsorption of glass wool boards. Silica aerogel-glass wool composites were prepared by glass wool and silica aerogel with liquid binder. Mixtures with binder were composed of CMC (carboxymethyl cellulose) and silica aerogel for glass wool board. Silica aerogel-glass wool composite boards were had $0.065g/cm^3$ density by impregnation silica aerogel where from origin glass wool board at $0.048g/cm^3$ density. Thermal conductivity of silica aerogel-glass wool composites were 0.0315 W/mK (up to 7.4% thermal resistance) and fire penetration time came to 362 seconds (up to 2.7 times stronger than origin glass wool board). In addition, hydrophobic aerogel characteristics prevented the adsorption of water onto silica aerogel-glass wool composite boards that was good for lightweight.

• Polymer(Korea)
• /
• v.36 no.3
• /
• pp.275-280
• /
• 2012

Poly(amic acid)s were successfully synthesized from 1,4-bis(4-aminophenoxy)benzene (1,4-APB) or 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane (HFBAPP) with pyromellitic dianhydride (PMDA), 3,3'-4,4'-benzopenonetetracarboxylic dianhydride (BPDA) and $p$-phenylenediamine ($p$-PDA) and then they were effectively converted into polyimide films by thermal imidization. The chemical structure and thermo-mechanical properties of polyimide films were examined using Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analyzer (TGA), thermo-mechanical analyzer, dynamic mechanical analyzer (DMA) and universal tensile machine (UTM). The moisture absorption, thermal and mechanical properties of polyimide films decreased with increasing the amount of 1,4-APB and HFBAPP. The polyimide films using HFBAPP showed lower properties than that of 1,4-APB at the same ratio, but it displayed better thermal properties and lower moisture absorption at the similar coefficient of thermal expansion (CTE) with a copper. On the basis of our finding, it is concluded that 4-component polyimide films could be utilized for base films for flexible copper clad laminates (FCCL) of flexible printed circuit boards.