• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.145-156
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• 2019

As the industrial desire for a step change in productivity within the manufacture of composite structures increases, so does the interest in Through-Thickness Reinforcement technologies. As manufacturers look to increase the production rate, whilst reducing cost, Through-Thickness Reinforcement technologies represent valid methods to reinforce structural joints, as well as providing a potential alternative to mechanical fastening and bolting. The use of tufting promises to resolve the typically low delamination resistance, which is necessary when it comes to creating intersections within complex composite structures. Emerging methods include the use of 3D woven connectors, and orthogonally intersecting fibre packs, with the components secured by the selective insertion of microfasteners in the form of tufts. Intersections of this type are prevalent in aeronautical applications, as a typical connection to be found in aircraft wing structures, and their intersections with the composite skin and other structural elements. The common practice is to create back-to-back composite "L's", or to utilise a machined metallic connector, mechanically fastened to the remainder of the structure. 3D woven connectors and selective Through-Thickness Reinforcement promise to increase the ultimate load that the structure can bear, whilst reducing manufacturing complexity, increasing the load carrying capability and facilitating the automated production of parts of the composite structure. This paper provides an overview of the currently available methods for creating intersections within composite structures and compares them to alternatives involving the use of 3D woven connectors, and the application of selective Through-Thickness Reinforcement for enhanced damage tolerance. The use of tufts is investigated, and their effect on the load carrying ability of the structure is examined. The results of mechanical tests are presented for each of the methods described, and their failure characteristics examined.

• Composites Research
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• 제16권6호
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• pp.41-47
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• 2003

복합재료는 비강성, 비강도가 높고 열팽창 계수가 낮으며 우수한 내열 특성 등 기계적, 열적 특성이 좋아 항공기, 인공위성을 비롯하여 여러 다른 구조물에 폭넓게 사용되고 있다. 하지만, 복합재료를 고온 환경에 사용하기 위해서는 고온 환경에서의 물성에 대한 검증이 필요하다. 본 연구에서는 FBG 센서가 삽입된 T700/Epoxy 복합재료 시편에 대해 온도에 따른 물성을 측정하였다 실험은 열챔버 내에서 수행하였고 온도 범위는 상온, $100^{\circ}$, $200^{\circ}$, $300^{\circ}$, $300^{\circ}$이다. 삽입된 광섬유의 예비 시험을 통해, 광섬유 센서의 삽입이 물성값에 미치는 영향을 확인하였다. 시험에는 [0/{0}/0]$_{T}$, [$90_2$/{0}/$90_2$] 와 같은 적층각을 갖는 두 종류의 시편을 사용하였다. 실험 결과로부터 온도에 따른 복합재료의 물성 변화를 성공적으로 측정하였으며 FBG 센서가 고온 환경의 변형률 측정 센서로 매우 적합함을 확인하였다.

• International Journal of Aerospace System Engineering
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• 제7권1호
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• pp.16-20
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• 2020

The recent trend is increasing towards the usage of polymer matrix composites since they have a wide variety of applications. They have applications in the field of aircraft and space industry, sporting goods, medical devices, marine and automotive applications and also in commercial usage. The most commonly used fibre-reinforced polymer matrix composite is Glass fibre reinforced epoxy (GFRE) composite which is used in aviation, sports and automotive industries. However, the strength of GFRE composites is not adequate for structural applications. Therefore, the current research focuses on increasing the strength of GFRE composites by reinforcing with micro Graphite (Gr) particulates. The Gr used is an ultra-fine powder with particle size 250 ㎛. Gr is known to have good wear resistance, thermal conductivity and can operate at high temperatures. Gr particulates are mixed with the epoxy matrix in various weight ratios. Hand-lay technique is used for fabricating the composites. Mechanical properties such as tensile strength, elongation, compressive strength and flexural strength are obtained experimentally to study the effect of change in Gr content (0-5 wt. %). The tests were done as per ASTM standards.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.29-43
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• 2016

Composite materials are rapidly gaining popularity as an alternative to metals for structural and load bearing applications in the aerospace, automotive, alternate energy and consumer industries. With the advent of thermoplastic composites and advances in recycling technologies, fully recyclable composites are gaining ground over traditional thermoset composites. Stamp forming as an alternative processing technique for sheet products has proven to be effective in allowing the fast manufacturing rates required for mass production of components. This study investigates the feasibility of using the stamp forming technique for the processing of thermoplastic, recyclable composite materials. The material system used in this study is a self-reinforced polypropylene composite material (Curv$^{(R)}$). The investigation includes a detailed experimental study based on strain measurements using a non-contact optical measurement system in conjunction with stamping equipment to record and measure the formability of the thermoplastic composites in real time. A Design of Experiments (DOE) methodology was adopted to elucidate the effect of process parameters that included blank holder force, pre heat temperature and feed rate on stamp forming. DOE analyses indicate that feed rate had negligible influence on the strain evolution during stamp forming and blank holder force and preheat temperature had significant effect on strain evolution during forming.

• International Journal of Aeronautical and Space Sciences
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• 제15권1호
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• pp.32-43
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• 2014

Automatic fiber placement (AFP) has become a popular processing technique for composites in the aerospace industry, due to its ability to place prepregs or tapes precisely in the exact position when complex parts are being manufactured. This paper presents the design, analysis, and manufacture of an AFP mandrel for composite aircraft fuselage skin fabrication. According to the design requirements, an AFP mandrel was developed and a numerical study was performed through the finite element method. Linear static load analyses were performed considering the mandrel structure self-weight and a 2940 N load from the AFP machine head. Modal analysis was also performed to determine the mandrel's natural frequencies. These analyses confirmed that the proposed mandrel meets the design requirements. A prototype mandrel was then manufactured and used to fabricate a composite fuselage skin. Material load tests were conducted on the AFP fuselage skin curved laminates, equivalent flat AFP, and hand layup laminates. The flat AFP and hand layup laminates showed almost identical strength results in tension and compression. Compared to hand layup, the flat AFP laminate modulus was 5.2% higher in tension and 12.6% lower in compression. The AFP curved laminates had an ultimate compressive strength of 1.6% to 8.7% higher than flat laminates. The FEM simulation predicted strengths were 4% higher in tension and 11% higher in compression than the flat laminate test results.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.153-157
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• 2001

Interfacial properties and microfailure modes of electrodeposition (ED) treated carbon fiber reinforced polyetherimide (PEI) toughened epoxy composite were investigated using microdroplet test and the measurement of surface wettability. As PEI content increased, Interfacial shear strength (IFSS) increased due to enhanced toughness and plastic deformation of PEI. In the untreated case, IFSS increased with adding PEI content, and IFSS of pure PEI matrix showed the highest. On the other hand, for ED-treated case IFSS increased with PEI content with rather low improvement rate. The work of adhesion between fiber and matrix was not directly proportional to IFSS for both the untreated and ED-treated cases. The matrix toughness might contribute to IFSS more likely than the surface wettability. Interfacial properties of epoxy-PEI composite can be affected efficiently by both the control of matrix toughness and ED treatment.

• Composites Research
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• 제27권4호
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• pp.152-157
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• 2014

Non-destructive testing methods of composite materials are very important for improving material reliability and safety. AE measurement is based on the detection of microscopic surface movements from stress waves in a material during the fracture process. The examination of AE is a useful tool for the sensitive detection and location of active damage in polymer and composite materials. FBG (Fiber Bragg Grating) sensors have attracted much interest owing to the important advantages of optical fiber sensing. Compared to conventional electronic sensors, fiber-optical sensors are known for their high resolution and high accuracy. Furthermore, they offer important advantages such as immunity to electromagnetic interference, and electrically passive operation. In this paper, the crack detection capability of AE (Acoustic Emission) measurement was compared with that of an FBG sensor under tensile testing and buckling test of composite materials. The AE signals of the PVDF sensor were measured and an AE signal analyzer, which had a low pass filter and a resonance filter, was designed and fabricated. Also, the wavelength variation of the FBG sensor was measured and its strain was calculated. Calculated strains were compared with those determined by finite element analysis.

• Elastomers and Composites
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• 제34권5호
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• pp.407-413
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• 1999

비세라믹 복합절연소재는 기계적 물성, 환경문제, 대량생산과 용이한 설계등의 우수한 특성으로 인해 전력산업분야에서 관심의 대상이 되어왔다. 또한 세라믹 절연체에 비하여 가볍고, 더욱 강인한 물성을 가진다는 장점이 있다. 본 연구에서는 뛰어난 전기 절연 특성과 우수한 내열, 내산화, 내오존성과 내후성을 가진 ethylene propylene diene monomer(EPDM)를 절연소재로 사용하였다. 특히, EPDM은 다른 고무 복합체에 비해 우수한 소수성을 가지기 때문에 장기간 사용이 가능하다는 점에서 본 연구에서는 EPDM 복합체의 유변학적 물성, 전기적물성, 그리고 접촉각의 측정을 통한 소수성 및 회복력에 관한 연구를 하였다. 또한 SEM을 사용하여 표면 형태학적 연구를 수행하였다.

• 한국재료학회지
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• 제5권1호
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• pp.75-86
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• 1995

현재 계획중인 항공우주상업과 관련된 부품을 제조하여 생산하기 위해서는 사용된 재료가 설계요구조건에 적합한지가 평가되어야 한지만 국내에서는 항공기나 우주비행체를 개발한 경험이 없으므로 평가체제가 확립되어 있지 않다. 따라서 항공기 및 우주비행체의 내구성과 안전성확보에 필요한 재료의 인정방법을 정의할 필요가 있다. 본 기고에서는 항공우주 선진국에서 수행하고 있는 재료 및 가공공정의 합치성 결정에 필요한 특성시험을 고찰하고, 우주환경에 의한 재료특성 변화와 항고기용 복합재료 평가의 예를 제시하여, 국내의 항공우주용 재료 평가체제 확립의 기초가 되도록 하였다.

• Composites Research
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• 제28권6호
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• pp.402-407
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• 2015

It is well known that the polymer matrix composite materials have good specific strength, making them appropriate for use in transport vehicle. Since the property of composite materials can be obtained only after manufacturing parts, the property depends on greatly on the fabrication process, which is different from metallic system. Therefore, in order to use composite materials for aircraft, the certifying agency requires a robust database with extensive tests and proof of the process unlike metals. Recently developed material qualification methodology by NCAMP (National Center for Advanced Materials Performance) has been accepted by FAA and EASA and can be applied to type certificate reducing time and cost of developing a composite materials database for aircraft application. This paper summarizes a study to establish the composite materials database to apply the NCAMP methodology to composite materials characterization for composite aircraft and to provide the effective materials database through Aerospace Composite Materials Data Center to be approved by Korea Civil Aviation Certification Agency.