• Composites Research
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• v.27 no.2
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• pp.77-81
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• 2014

In this study, it was performed damage assessment and repair of small scale aircraft adopted on composite. This aircraft adopted the sandwich structure to skin of wing. This study aims to investigate the residual strength of sandwich composites with nomex honeycomb core and carbon fiber face sheets after the open hole damage by the experimental investigation. The 4-point bending tests were used to find the bending strength, and the open hole was applied to introduce the simulated damage on the specimen. The bending strength test results after open hole were compared with the results of no damaged specimen test. In addition, The damaged composite structure was repaired using external patch repair method after removing damaged area. After that, this study presents comparison results of the experimental investigation between the damaged and the repaired specimen. It was found that the bending strength of repaired specimen was recovered up to 95% of undamaged specimen.

• Composites Research
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• v.31 no.5
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• pp.238-245
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• 2018

The hydrodynamic ram (HRAM) phenomenon is one of the main types of ballistic battle damages of a military aircraft and has great importance to airframe survivability design. The HRAM effect occurs due to the interaction between the fluid and structure, and damage can be investigated by measuring the pressure of the fluid and the dynamic strains on the structure. In this paper, HRAM test of a composite T-Joint was performed using a ram simulator which can generate HRAM pressure. In addition, calibration tests of PVDF sensor were performed to determine the circuit capacitance and time constant of the measurement system. The failure behavior of the composite T-Joint due to HRAM pressure was examined using the strain gauges and a PVDF sensor which were attached to the surface of the composite T-Joint.

• Journal of Aerospace System Engineering
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• v.11 no.4
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• pp.1-7
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• 2017

The development of effective design allowable values for unmanned composite aircraft is an issue of paramount concern for the industry. The application of conventional manned aircraft structural certification methods to unmanned aircraft such as prototype and technology demonstrators, can lead to excessively long development time and costs. In this paper, the determining method of composite structure design allowable values for light composite unmanned aircraft is presented to reduce to the structural weight. This paper seeks to show the applicability of composite B-basis material values as a design allowable of light composite unmanned aircraft structures. A review of different civil and UAV targets failure probability is given. From the results, the researchers can know that the requirements of light composite unmanned aircraft design allowable should be alleviated, compared to manned composite aircrafts.

• Journal of Digital Convergence
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• v.17 no.9
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• pp.79-88
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• 2019

This study analyzes the influential factors and patterns associated with death from aircraft accidents and incidents using data mining techniques. To this end, we used two datasets for aircraft accidents and incidents, one from the National Transportation Safety Board (NTSB) and the other from the Federal Aviation Administration (FAA). We developed our prediction models using the decision tree classifier to predict death from aircraft accidents or aircraft incidents and thereby derive the main cause factors and patterns that can cause death based on these prediction models. In the NTSB data, deaths occurred frequently when the aircraft was destroyed or people were performing dangerous missions or maneuver. In the FAA data, deaths were mainly caused by pilots who were less skilled or less qualified when their aircraft were partially destroyed. Several death-related patterns were also found for parachute jumping and aircraft ascending and descending phases. Using the derived patterns, we proposed helpful strategies to prevent death from the aircraft accidents or incidents.

• Composites Research
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• v.15 no.4
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• pp.9-16
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• 2002

With the wide application of fiber-reinforced composite material in aero-structures and mechanical parts, the design of composite joint have become a very important research area because they are often the weakest areas in composite structures. In this paper, the failure area index method to predict the strength of the mechanically fastened composite joint which has the same stacking sequence was suggested and evaluated. By the suggested failure area index method, the strength of the mechanically fastened composite joint could be predicted within 6.03％.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.709-713
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• 2017

In urgent situations such as crashes, the integrity of an aircraft's fuel tank is directly related to the survivability of the crew. Thus, an external auxiliary fuel tank should be robust against bird strikes. In this study, a numerical analysis was carried out using impact analysis software to analyze the influence of bird strike on a composite container for an external auxiliary fuel tank. The structure was modeled as a shell element, and the fluid and bird were modeled by the particle method. The behavior of the internal fluid was also examined. The maximum stress, deformation, and strain of the composite container were also calculated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.8
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• pp.889-895
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• 2012

Carbon fiber reinforced plastic (CFRP) composites have high specific stiffness and high specific strength. Therefore, they are increasingly being use, instead of conventional metallic materials in the aviation and automobile industries, where there is a strong demand for lightweight materials. In aircraft, the fuselage is exposed to severe conditions of high temperatures and high humidity. Therefore, it is necessary to estimate the strength of CFRP composites under real conditions from the viewpoint of aircraft safety. In this study, CFRP specimens were immersed in distilled water at $75^{\circ}C$ for a long time. Then, tensile tests were performed on these specimens, and the fracture characteristics of the fractured surfaces were analyzed using SEM. A fatigue test was performed on specimens immersed for 300 days with R=0.1, and it was confirmed that the fatigue life deteriorated in immersed specimens compared to specimens that were not immersed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.5
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• pp.462-471
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• 2008

Flight recoder is used to analyze the accident factors and prevent the accident. In the analysis of the flight recorder, the most important factor is how to estimate the precise location of the flight. Traditional aviation navigation is based on stable sensors such as DME and VOR. In order to enhance the precision of the location estimation, the integrated navigation algorithm is designed to incorporate DME, Air data sensors and INS(Inertial Navigation System). The results demonstrate that the proposed algorithm can achieve better accuracy, comparing with the traditional navigation schemes, in flight location estimation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.12-22
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• 2012

Performance variation of autorotating rotor was investigated. The shaft angle of the rotor is reduced while the flight velocity is increased. The BO-105 helicopter rotor blade was replaced by untwisted NACA 0012 airfoil and the rotor was simulated by using Transient Simulation Method(TSM) to judge the autorotation region for the variables. To simulate the compressibility effect at high speed flight, two-dimensional aerodynamic data was analyzed by compressible Navier-Stokes solver and Pitt/Peters inflow theory was adopted to simulate the induced velocity field. Thrust and lift coefficients, lift to drag ratio variations were investigated, also the lift and power were compared to those of BO-105 helicopter. Sharing lift and power between the autorotating rotor and wing was considered when the compound aircraft concept is introduced.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.5
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• pp.319-325
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• 2019

The main purpose of this study is to compare the bird strike analysis result of the radome composed of composite laminate and sandwich structure attached to aircraft with test result. First of all, we generated bird model which has water properties through SPH(Smoothed Particle Hydrodynamics) method. And then bird strike analysis was conducted with initial velocity of bird measured from bird strike test. From analysis result we investigated whether structural failure occurred or not onto the radome and compare maximum displacement of the radome structure with test result. Also reliability of numerical analysis model was confirmed through time-dependent pressure trend on this collision process matched existing research result. Furthermore, we confirmed that failure behavior of the radome can be affected by density of the particles in the bird model.