• Composites Research
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• v.32 no.5
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• pp.199-205
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• 2019

The composite material has the advantage that the fibers can be arranged in a desired direction and can be manufactured in one piece. However, micro voids can be formed due to micro air, moisture or improper curing temperature or pressure, which may cause the deterioration in mechanical strength. In this paper, the composite panels with different thicknesses were made by varying the curing pressure in an autoclave vacuum bag process and their microporosities were evaluated. Microporosity was measured by image analysis method, acid digestion method, and combustion method and their correlation with ultrasonic attenuation coefficient was analyzed. From the test results, it was found that the acid digestion method had the highest accuracy and the lower the curing pressure, the higher the microporosity and the ultrasonic attenuation coefficient. In addition, the microporosity and the ultrasonic attenuation coefficient were increased as the thickness of the composite panel was increased at the same curing pressure.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.17-17
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• 2012

수송용 섬유소재는 자동차, 항공기 또는 선박 등의 교통 및 운송 분야에 기여하는 사용되는 섬유소재를 말하며, 내장재, 각종 호스류, 벨트류, 타이어, 안전용품, 필터류 등을 포함하고 일반적으로 섬유, 발포체, 고무, 플라스틱, 접착제 등 유기소재가 결합된 복합체이다. 기존 섬유기술의 혁신과 더불어 IT, NT, BT, ET 등 첨단 기술과의 융합에 의한 고성능 극한 슈퍼섬유, 나노 복합섬유 등의 신소재를 개발하여 산업 전반에서 플라스틱의 금속소재 대체수요를 증가시키고 산업자재의 고성능화, 고기능화, 다양화를 이루기 위해 다양한 노력이 진행하고 있다. 현재 수송용 섬유소재 산업은 기술의 연결고리가 부족하며, 선도기업 및 원천기술이 부족하며, 자동차용 섬유부품소재 관련 기업의 역량도 부족한 실정이다. 이에 광역경제권 연계협력사업을 통해 생산기반의 대경권(대구경북)과 수요중심의 동남권(부산경남)의 네트워크를 강화하여 완성품 업체 및 수요기업과의 네트워킹을 강화하고자 한다. 따라서 본 연구에서 수송용 섬유소재개발, 수송용 친환경 oam-skin 일체형 표피재 개발, 고속성형 복합소재 및 수송용 경량부품 개발, 초경량 고내열 고강도 섬유활용 하이브리드 wire & cable 개발 등 수송용 섬유소재를 개발하고, 또한 수송용 섬유소재의 생산-수요 연계를 통한 투자활성화, 기술개발, 소재 산업 육성을 강화하여, 산학연네트워크구축, 지역 간 협력 및 국제적 협력, 생산-수요기반의 연계협력시스템을 활용한 자립형 수송용 소재 공급기지 완비하는 데 목적이 있다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.2
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• pp.119-128
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• 2010

The hygrothermal effect on the strength of composite single-lap bonded joints were investigated. The specimens were manufactured in four different manufacturing methods and tested in three different environmental conditions. An interesting result is that the strengths of the joints in the elevated temperature and wet (ETW) conditions were found to be 11 ~ 23% higher than those in the room temperature and dry (RTD) environment. In contrast, the strengths of the joints in the cold temperature and dry (CTD) condition decrease by 8 ~ 21% compared to those in the RTD environment except for cobonded joint. The difference in the strength by testing environments is mainly attributed to the change of the material properties of adhesive by temperature and moisture.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.10
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• pp.3199-3210
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• 1996

The buckling and postbuckling behaviors were sutdied analytically and experimentally for stiffened laminated composite panels under compression loading. The panels with I-, blade, -and hat-shapeed stiffeners were investigated. In the analysis, the stiffened panels were anlyzed using the nonlinear finite element method combined with an improved arc-length method. The progressive failure analysis was done by adopting the maximum stress criterion and complete unloading failure model. The effects of the fiber angles were investigated on the buckling and postbuckling behaviors. In the experiment, the web and the lower cap of each stiffener were formed by the continuous lay-up of the skin for cocuring the stiffened panels. Therefore, the separation between stiffener and skin was not found in the junction part even after postbuckling ultimate load and the stiffened panels had excellent postbuckling load carrying capacity. A shadow moire thchnique was used to monitor the out-of-plane deformations of the panels. The piezoelectric films were attached to the panels to get the failure characteristics of the panel. The analytical results on the buckling load, postbuckling ultimate load, and failure pattern showed good agreement with the experimental results.

• Composites Research
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• v.31 no.6
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• pp.323-331
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• 2018

The effect of stainless steel jagged-pin reinforcement on the pull-off strength of the composite hat-joint was studied by the test. The pins were physically and chemically surface-treated and inserted in the thickness direction over the interface where the skin and stiffener meet. The specimens including the jagged-pins were made by co-curing process. Diameters of the jagged-pins were 0.3, 0.5 and 0.7 mm. The pin areal densities were set to 0.5 and 2.0% based on the interface area where the skin and stiffener meet. The specimens using 0.3 mm diameter normal (un-jagged) pins with 2.0% areal density were additionally fabricated and tested to investigate the pin shape effect on the pull-off strength. The pull-off strengths of specimens reinforced with 0.5% areal density by 0.3, 0.5, and 0.7 mm diameter pins were 45, 19 and 9% higher than those of un-reinforced specimens, respectively. In case with 2.0% pin areal density, the strengths were 127, 45, and 11% higher than those of un-reinforced specimens, respectively. The test results show that the higher pin areal density results in the higher strength when the pin diameter is the same. When the pin areal density is the same, the smaller pin diameter leads to higher strength. When the joints using jagged-pins and normal pins in 2.0% areal density with 0.3 mm diameter, the joints of jagged-pins showed the 64% higher strength. From the results of this study, it was confirmed that jagged-pin reinforcement can be an effective method for improving the pull-off strength of composite hat-joint.