• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.623-623
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• 2016

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.100-108
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• 2015

The purpose of this study is to evaluate the effect of improvement on the impact resistance and strength properties of cement composites by surface modification of aramid fiber. For aramid fiber reinforced cement composites, therefore, dispersion capability and the bonding efficiency between the fibers and the cement composite material need to be improved. It is possible by modifying surface properties to hydrophobic, it is considered that oiling agent ratio of 1.2 % and improvement of performance is in need to be investigated. In this study, short aramid fibers were mixed by different fiber length and oiling agent ratio. And improvement of strength properties and impact resistance performance of hybrid cement composites were evaluated under the influence of steel fiber. As a result, strength properties of aramid fiber reinforced cement composites are different by mixing ratio of fiber, oiling agent ratio and length of fiber. In case of cement composites which have same volume fraction and fiber length, tensile strength and flexural strength were improved with increase of the emulsions throughput of the fiber surface. The results of evaluation on the static strength properties had effects on impact resistance performance by high-velocity impact. And it was observed that the scabbing of rear was suppressed with increase of the oiling agent ratio.

• Journal of Korean Association for Spatial Structures
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• v.10 no.4
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• pp.75-83
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• 2010

Laminated composite plates have shown their superiority over metals in applications requiring high specific strength, high specific modulus, and so on. Therefore, they have used in various industry. However, they have poor resistance to impact compared to typical metal materials. So, many researchers have investigated about impact behavior of laminated composite plate. To investigate impact behavior of laminated composite plate, we have to calculate contact force between impactor and laminated composite plate at the first. Impactor's equation of motion, plate's equation of motion and correlations for indentation were solved to know the contact force at the same time. In this study, low velocity impact behavior of composite plate was investigated using the finite element program which is involved the classical Hertzian law, Sun's law and Sun & Yang's experimental law and Sun & Tan's experimental law considering the stacking method.

• Composites Research
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• v.31 no.5
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• pp.215-220
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• 2018

In this study, finite element analysis of Carbon-Steel Laminates with different layup pattern was conducted to verify similarity to the results of previous studies and to develop the effective model for low-velocity impact analysis. As in the experiment, Finite element analysis of the Fiber metal laminates (FMLs) with five different lamination patterns was carried out, and the impact resistance of the FMLs was confirmed by comparing the energy absorption ratio. The FMLs showed the higher energy absorption ratio than the mild steel having the same thickness, and it was confirmed that all the FMLs had the high energy absorption ratio over than 96%. In addition, the low-velocity impact analysis model proposed in this study can be effectively used to study composite forms and automotive structures.

• Biomaterials and Biomechanics in Bioengineering
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• v.3 no.1
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• pp.47-57
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• 2016

Results from multiple high profile experiments on the parameters influencing the impacts that cause skull fractures to the frontal, temporal, and parietal bones were gathered and analyzed. The location of the impact as a binary function of frontal or lateral strike, the velocity, the striking area of the impactor, and the force needed to cause skull fracture in each experiment were subjected to statistical analysis using the JMP statistical software pack. A novel neural network model predicting skull fracture threshold was developed with a high statistical correlation ($R^2=0.978$) and presented in this text. Despite variation within individual studies, the equation herein proposes a 3 kN greater resistance to fracture for the frontal bone when compared to the temporoparietal bones. Additionally, impacts with low velocities (<4.1 m/s) were more prone to cause fracture in the lateral regions of the skull when compared to similar velocity frontal impacts. Conversely, higher velocity impacts (>4.1 m/s) showed a greater frontal sensitivity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.820-824
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• 1997

In order to investigate the effect of surface treatment(Anodizing) and rolling in Al 5083-H131 alloy, ballistic testing was conducted. Ballistic resistance of these materials. was measured by protection ballistic limit(V$_{50}$), a statical velocity with 50% probability for incomplete penetration. Fracture behaviors and ballistic tolerance, described by penetration modes, are observed respectfully, resulting from V$_{50}$ test and Projectile Through Plates(PTP) test at velocities greater than V$_{50}$. PTP tests were conducted with 0$^{\circ}$obliquity at room temperature were also conducted with projectiles that were able to achieve near or complete penetration during PTP tests. Resistance to penetration, and penetration modes of Al 5052-H34 alloy, compared to those of Al 5083-H131 alloy.alloy.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.3
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• pp.178-186
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• 2003

In order to investigate the fracture behaviors (penetration modes) and the resistance to penetration during ballistic impact of Al 5052-H34 alloy laminates, cold-rolled Al 5052-H34 alloy laminates, anodized Al 5052-H34 alloy laminates, and anodized Al 5052-H34 alloy after cold-rolling, a ballistic testing was conducted. In general, superior armor materials are brittle materials which have a high hardness. Ballistic resistance of these materials was measured by a protection ballistic limit (V$_{50}$), a statistical velocity with 50% probability fur incompletete penetration. Fracture begaviors and ballistic tolerance, described by penetration modes, ate observed from the results from the results of V$_{50}$ test and Projectile Through Plates (PTP) test at velocities greater than V$_{50}$, respectively. PTP tests were conducted with 0$_{\circ}$obliquity at room temperature using 5.56mm ball projectile. V$_{50}$ tests with 0$_{\circ}$obliquity at room temperature were concucted with projectiles that could achieve neat or complete penetration during PTP tests. Surface hardness, resistance to penetration, and penetration modes of Al 5052-H34 alloy laminates are compared to those of cold-rolled Al 5052-H34 alloy laminates and anodized Al 5052-H34 alloy laminates and anodized Al 5052-H34 cold-rolled alloy.

• Advances in Computational Design
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• v.1 no.2
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• pp.139-154
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• 2016

The usage of sandwich structure is extensively increasing in lightweight protective structures due to its low density and other useful properties. Sandwich panels made of metal sheets with unfilled cellular cores are found to exhibit lower deflections by comparing to an equivalent monolithic plate of same metal and similar mass per unit density. However, the process of localized impact on solid structures involving plastic deformation, high strain rates, temperature effect, material erosion, etc. does not hold effectively as that of monolithic plate. In present work, the applications of the sandwich plate with corrugated core have been extended to develop optimized lightweight armour using foam as medium of its core by explicit finite element analysis (FEA). The mechanisms of hardened steel projectile penetration of aluminum corrugated sandwich panels filled with foams have been numerically investigated by finite element analysis (FEA). A comparative study is done for the triangular corrugated sandwich plate filled with polymeric foam and metallic foam with different densities in order to achieve the optimum penetration resistance to ballistic impact. Corrugated sandwich plates filled with metallic foams are found to be superior when compared to the polymeric one. The optimized results are then compared with that of equivalent solid and unfilled cores structure to observe the effectiveness of foam-filled corrugated sandwich plate which provides an effective resistance to ballistic response. The novel structure can be the alternative to solid aluminum plate in the applications of light weight protection system.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.99-106
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• 2013

Concrete materials subjected to impact by high velocity projectiles exhibit responses that differ from those when they are under static loading. Projectiles generate localized effects characterized by penetration of front, spalling of rear and perforation as well as more widespread crack propagation. The magnitude of damage depends on a variety of factors such as material properties of the projectile, impact velocity, the mass and geometry as well as the material properties of concrete specimen size and thickness, reinforcement materials type and method of the concrete target. In this study, penetration depth of front, spalling thickness of rear and effect of spalling suppression of concrete by fiber reinforcement was evaluated according to compressive strength of concrete. As a result, it was similar to results of the modified NDRC formula and US ACE formula that the more compressive strength is increased, the penetration depth of front is suppressed. On the other hand, the increase in compressive strength of concrete does not affect spalling of rear suppression. Spalling of rear is controlled by the increase of flexural, tensile strength and deformation capacity.

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.715-726
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• 2023

This study suggested that protective panels should be installed as sacrificial members as a safety design method for structures with potential explosions such as hydrogen charging stations to minimize direct damage to the structure and have resilience. To this end, the focus of the experiment is on quantitatively evaluating the impact of the structure when the protection panel is installed closely or spaced apart from the structure in a high-speed collision situation of the projectile. The experimental design used steel plates instead of concrete structural members mainly used in the past for excellent reproducibility, and the impact of structural members was compared and analyzed through deformation differences on the back of the steel plate. In addition, the impact of changes in the physical properties of the elastic body used as a separation material for the protective member and the difference in shock wave transmission time according to the protective member and the elastic body on the structural member was investigated.