• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.3
• /
• pp.288-294
• /
• 2018

Recently, as the speed and performance of the launcher and the missile have been improved, it is necessary to consider the acoustic load of launching and flight in initial design step. In this paper, an experimental study on acoustic absorption and transmission characteristics of aluminium vs. sandwich composite structures were conducted. The overall noise reduction was evaluated by performing an acoustic test in the reverberation room, and the acoustic absorption and transmission loss of the structures were analyzed by conducting the sound absorption test inside the structure.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.21 no.4
• /
• pp.422-428
• /
• 2018

Increase in use of lightweight structures, coupled with the increased acoustic loads resulting from larger and longer range guided missiles, has made missile more susceptible to failures caused by acoustic loads. Thus, accurate prediction of acoustic environment and the response is becoming ever more important for mission success. In this paper, the acoustic response of a sandwich composite skin structure to diffuse acoustic excitation is predicted over a broad frequency range. For the low frequency acoustic analysis, coupled FE-BEM method is used where the structure is modeled using FEM and the interior and exterior fluid is modeled using BEM. For the high frequency region, statistical energy analysis is applied. The predicted acoustic level inside the structure is compared with the result from acoustic test conducted in reverberation chamber, which shows very good agreement.

• Composites Research
• /
• v.22 no.2
• /
• pp.24-29
• /
• 2009

This study aims to investigate the residual strength of sandwich composites with Al honeycomb core and carbon fiber face sheets after the quasi-static indentation damage by the experimental investigation. The 3-point bending test and the edge-wise compressive strength test were used to find the mechanical properties, and the quasi-static point load was applied to introduce the simulated damage on the specimen. The damaged specimens were finally assessed by the 3-point bending test and the compressive strength test. The investigation results revealed the residual strength of the damaged specimens due to the quasi-static indentation. The both test results showed that the residual strength of the damaged specimen was decreased according to increases of the damaged depth.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.1
• /
• pp.29-34
• /
• 2010

In this study, joint strength and failure characteristics were experimentally examined with pull-out and shear specimens in which new designed "high strength insert" was applied. The performance of the new insert was compared with typical insert design. The experimental results showed that the "high strength insert" had the joint strengths of 2.1 times in the pull-out specimens and 2.04 times in the shear specimen compared with typical insert joints. Therefore, the new developed "high strength insert" will be usefully used in the aerospace structure.

• Smart Structures and Systems
• /
• v.12 no.5
• /
• pp.483-499
• /
• 2013

A new piezoceramic $d_{15}$ shear-induced torsion actuation mechanism representative benchmark is proposed and its experimentations and corresponding 3D finite element (FE) simulations are conducted. For this purpose, a long and thin smart sandwich cantilever beam is dimensioned and built so that it can be used later for either validating analytical Saint Venant-type solutions or for analyzing arm or blade-based smart structures and systems applications. The sandwich beam core is formed by two adjacent rows of 8 oppositely axially polarized d15 shear piezoceramic patches, and its faces are dimensionally identical and made of the same glass fiber reinforced polymer composite material. Quasi-static and static experimentations were made using a point laser sensor and a scanning laser vibrometer, while the 3D FE simulations were conducted using the commercial software $ABAQUS^{(R)}$. The measured transverse deflection by both sensors showed strong nonlinear and hysteretic (static only) variation with the actuation voltage, which cannot be caught by the linear 3D FE simulations.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.11 no.4
• /
• pp.149-158
• /
• 2008

This article provides strength estimation of T-joint area which made of composite material. Inner and outer structures of medium range surveillance radar are all made of sandwich structure which is made with composite material(CFRP) and aluminum honeycomb core. Since the radar is voluminous and has very complex inner structure, the whole structure cannot be made as one piece. Therefore, usage of T-joints is inevitable. Since some of stress concentration areas were located around T-joint area, series of strength estimations were conducted. Three different configurations were tested to improve mechanical properties(primarily on strength). The results show an improvement on strength to meet calculated strength on stress concentrated T-joint area.

• Proceedings of the KSME Conference
• /
• 2001.06c
• /
• pp.189-196
• /
• 2001

Machine tools of high-speed and high-precision are required for various fields of industry such as semiconductor, automobile, mold fabrication and so on. Light-weight machine tool structure is essential for reduction of production time through rapid transportation. Also, high damping capacity of the structure is required to obtain precise products without vibration during manufacturing. Composite materials have high potential for machine tool structures due to its high specific stiffness and good damping characteristics. In this study, the design and the manufacture of a hybrid machine tool structure using composite materials was attempted and the damping capacity was investigated experimentally.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2002.10a
• /
• pp.241-244
• /
• 2002

Recently, the size of glass panel is increased to $1250 mm{\times}1100 mm{\times}0.7 mm$, whose mass is 2.65 kg, which requires much stiffer robot structure. In addition to the high stiffness, the robot hands and wrists for glass panel handling should have miller surface finishing of its outer surface to prevent particles and dusts from adhering on the surface. The maximum height of the robot structure should not be larger than 1500 mm because other automated guided vehicles (AGV) and transfer equipments have been designed within this size limit. The difference of maximum deflections of the four ends of the hands before and after loading the glass panel should be less than 2.0 mm. In this work, the robot hands and wrists for handling large glass panel displays were designed based on the axiomatic design using the finite element method along with optimization routine.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2001.05a
• /
• pp.97-101
• /
• 2001

Composite materials have been applied widely in interior panels of buildings and transport vehicles. Recently good fire performance and weight reduction are key issues in the fields. In the present study we investigated effects of processing parameters on the performance of honeycomb sandwich panels, especially peel strength of the panel and fire performance. The processing parameters considered were types of matrix resin, resin contents, panel cure conditions, and surface painting process conditions. The results showed that the higher resin content provides the better peel strength. Controled cure steps are also needed to obtain good pee] strength. Paint processing parameters including base putty thickness and paint drying conditions and paint thickness are important to obtain good paint adhesion and good fire performance.

• Steel and Composite Structures
• /
• v.44 no.1
• /
• pp.91-104
• /
• 2022

The purpose of the present work is to study the parametric nonlinear vibration behavior of three layered symmetric laminated plate. In the analytical formulation; both normal and shear deformations are considered in the core layer by means of the refined higher-order zig-zag theory. Harmonic balance method in conjunction with Galerkin procedure is adopted for simply supported laminate plate, to obtain its natural and damping properties. For these aims, a set of complex amplitude equations governed by complex parameters are written accounting for the geometric nonlinearity and viscoelastic damping factor. The frequency response curves are presented and discussed by varying the material and geometric properties of the core layer.