Earticle

This study was carried out to develop bulletproof helmet with improved bulletproof performance. In modern warfare, the role of personal protection materials in combat is very important because of increase of personal safety. Bulletproof helmets are being developed in the advanced countries in consideration of complex factors such as bulletproof performance improvement and light weight for reducing combat load. In order to develop the bulletproof helmet with improved bulletproof performance to be used in the future, the bulletproof performance test method is presented. The test was carried out under various environmental conditions for the evaluation of the bulletproof helmet.

In the face of increasingly diversified combat environments and the rising importance of soldier survivability, the reliability of bulletproof equipment has emerged as a critical factor in modern military operations. However, the current defense system in Korea lacks a dedicated infrastructure for reliability assessment, leading to potential risks of equipment failure in real combat situations. This institutional gap results in both operational inefficiency and an underestimation of the economic value of soldier protection. To address this issue, this study conducts a cost-benefit analysis of establishing a reliability assessment infrastructure for bulletproof equipment. By incorporating both direct benefits (such as defect detection and maintenance efficiency) and indirect benefits (such as improved soldier survivability and reduced reliance on foreign certification), the analysis evaluates long-term returns over the period 2025–2059. The estimation employs expected utility theory and uses the value of a statistical life (VSL) to quantify survivability-related gains. The results reveal a substantial net present value (NPV) of approximately KRW 320 billion when survivability benefits are included, and KRW 127.6 billion even under the most conservative assumptions. These findings support the strategic necessity of implementing a systematic reliability evaluation framework, not only to enhance operational readiness but also to strengthen the economic sustainability and competitiveness of the domestic defense industry.

This study is to investigate the improvement of quality and cost reduction of welding materials for combat vehicles through localization. The existing imported welding wires and localized welding wires were evaluated. The evaluation of the welding wires was performed for the feedability, chemical/mechanical properties, macro testing, and weldability. As a result of evaluation, the localized welding material met all the evaluation standard values. In addition, it showed excellent performance in terms of weldability and feedability. It is judged that the welding quality is improved thanks to the improvement of feeding characteristics through the localization of the welding material, and the fatigue of the worker is also expected to be relieved.

In this study, the uncertainty in the ballistic test was calculated. Characteristic factor plots were used to identify the sources of uncertainty. The results are as follows. First, the uncertainty about the projectile was calculated to be 0.008m/s. Second, the uncertainty for depth measurement was calculated to be 0.03mm. The biggest factor influencing the uncertainty was the human error by the measurer. Therefore, in order to reduce the uncertainty, it is necessary to minimize human intervention by introducing automatic measuring equipment.

Soda-lime silicate (SLS) glass was strengthened by ion exchange for application of thin and lightweight bulletproof windows. The optimal conditions for ion exchanged SLS glass (thickness of 3 and 10 mm) at $480^{\circ}C$ were 10 and 17 min, respectively. The Vickers hardness values of the strengthened SLS glass samples with thicknesses of 3 and 10 mm were $5.9{\pm}0.22$ and $6.7{\pm}0.17GPa$, respectively, which values were about 22% higher than those of parent SLS glass. By laminating a multilayer defense film and polycarbonate sheet with ion exchanged SLS glass, we were able to make a thin and lightweight bulletproof window (24.25 mm, 4.57 kg, $50.06kg/m^2$, $V_{50}$ 901.8 m/s). As a result, the thickness of the bulletproof window was decreased by about 39% from 40 to 24.25 mm. The light transmittance in the visible range satisfied the standard (over 76%) for bulletproof windows.

Representative bulletproof materials, such as aramid or ultra-high molecular weight polyethylene(UHMWPE), have excellent strength and modulus in the plane direction but are very vulnerable to forces applied in the thickness direction. This paper reports a study on the effects of reinforcement in the thickness direction when bulletproof composite fabrics are prepared to improve their performance. Aramid and UHMWPE fabrics were combined using the film-bonding, needle-punching, or stitching methods and then subjected to low-velocity projectile and ball-drop impact tests. The results of the low-velocity projectile test indicated that the backface signature(BFS) decreased by up to 29.2% in fabrics obtained via the film-bonding method. However, the weight of the film-bonded fabric increased by approximately 23% compared with that obtained by simple lamination, and the fabric stiffened on account of the binder. Flexibility, light weight for wearability, and excellent bulletproof performance are very important factors in the development of bulletproof materials. When the needle-punching method was used, the BFS increased as the fibers sustained damage by the needle. When the composite fabrics were combined by stitching, no significant difference in weight and thickness was observed, and the BFS showed similar results. When a diagonal stitching pattern was employed, the BFS decreased as the stitching density increased. By contrast, when a diamond stitching pattern was used, the fabric fibers were damaged and the BFS increased as the stitching density increased.

Nacre of abalone shell features a "brick-and-mortar" microstructure, in which micro-plates of calcium carbonate are bonded by nanometers-thick layers of chitin and proteins. Due to the microstructure and its unique toughening mechanisms, nacre possesses an excellent combination of specific strength, stiffness and toughness. This study deals with the possibility of using nacre fragments obtained from abalone shell for making a bulletproof armor system. A composite plate laminated with abalone shell fragments is made and compression and bend tests are carried out. In addition, a bulletproof test is performed with hybrid armor systems which are composed of an alumina plate, a composite plate, and aramid woven fabric to verify the ballistic performance of nacre. The compressive strength of the composite plate is around 258.3 MPa. The bend strength and modulus of the composite plate decrease according to the plate thickness and are about 149.2 MPa and 50.3 GPa, respectively, for a 4.85 mm thick plate. The hybrid armor system with a planar density of $45.2kg/m^2$, which is composed of an 8 mm thick alumina plate, a 2.4 mm thick composite plate, and 18 layers of aramid woven fabric, satisfy the NIJ Standard 0101.06 : 2008 Armor Type IV. These results show that a composite plate laminated with abalone shell fragments can be used for a bulletproof armor system as an interlayer between ceramic and fabric to decrease the armor system's weight.

본 연구에서는 아직 수행되고 있지 않지만 향후 필요한 BRP(Bulletproof Reliability Program) 개념과 절차를 소개하고자 하였다. BRP 업무수행 체계는 다음과 같다. 먼저 국방부의 조정/통제 하에 기품원에서 연간 BRP 계획을 수립하고 시행을 주관한다. 다음으로 각 군 및 유관기관/부서의 의견을 수렴하여 BRP 대상 시료(Lot)를 선정하고 시험을 진행한다. 시험이 종료되면 종합된 결과를 각 군에 통보하며, 각 군에서는 후속조치를 수행한다. BRP 업무수행 절차는 매년 평가계획을 수립하는 사업(평가) 계획단계, 수립된 계획에 따라 일반검사, 기능시험, 운용시험 등을 수행하는 시험단계, 결과를 종합·분석하고 방탄물자의 성능 등을 감안하여 적정한 등급으로 판정하는 평가/분석단계, 그 결과에 따른 각 군의 후속조치 단계로 이루어져 있다. BRP 수행을 위한 제언은 다음과 같다. 첫째, 현재 일부 적체되는 시험물량과 개발 중인 워리어 플랫폼, 향후 발생할 BRP 물량을 적시에 시험하여 방탄물자의 적시 조달 및 장병의 안전성 향상, 국방예산의 절감을 위한 추가적인 시험장 건설이 필요하다. 둘째, 현재 사격시험만을 통한 방탄시험을 넘어 방탄물자의 신뢰성 평가방법을 개발하고 적용하는 것이 필요하다. 셋째, BRP가 장병의 안전성 보장 및 전투력 향상을 위한 필수적인 것임을 알리고 관련 업무의 시급성과 지원 필요성을 주요 관리자와 지휘관들에게 인식시키는 것이 필요하다.

This study examines the reliability evaluation concept and procedure of bulletproof materials (BRP: Bulletproof Reliability Program). ASRP, RAM analysis tasks were utilized for the study. Based on this analysis, the concept, method, performance system, and procedure of BRP were examined. The BRP task execution procedure consists of the following four steps. First, the business (evaluation) planning stage establishes the evaluation plan every year. Second, there is a testing stage that performs the general inspection, functional test, and operational test according to the established plan. Thirdly, there is an evaluation/analysis phase to synthesize/analyze the results and to judge the appropriate grade considering the performance of bulletproof materials. Finally, the follow-up step of each group according to the result. The following criteria are suggested for BRP implementation: BRP testing capability, development of BRP evaluation method, and recognition of the importance of BRP business.

This study investigated Kevlar fabric impregnated with shear thickening fluid (STF). The STF performance was assessed by comparing bullet-proof characteristics of STF impregnated and pure Kevlar material. The analysis employed a circular steel ball as the nominal warhead, and bulletproof characteristics were evaluated by the warhead residual velocity. Various initial velocity conditions were employed, with different bulletproof characteristics apparent for each velocity region. The results of this study provide effective data for future bulletproof material design and application.

Borosilicate glass(GVB-Solutions in glass, 2mm, Germany) was prepared in the composition of $80.4SiO_2-4.2Na_2O-2.4Al_2O_3-13.0B_2O_3$. The 2-step crystallization was performed around $584^{\circ}C$ of glass transition temperature ($T_g$), and $774^{\circ}C$ of crystallization temperature($T_c$). The maximum nucleation rate was $8.8{\time}10^9/mm^3{\cdot}hr$ at $600^{\circ}C$ and the maximum crystal growth rate was 3.5nm/min at $750^{\circ}C$. The maximum mechanical properties were observed at 22.8% of volume fraction, the strength, hardness and fracture toughness was 555MPa, $752kg/mm^2$, $1.082MPa{\cdot}mm^{1/2}$. The crystal size of 177nm which has volume fraction of 22.8% showed maximum strength of 562MPa, it is about 157% higher than parent borosilicate glass. From these results, the crystallized borosilicate glass can be applied weight lighting of bullet proof materials.

Purpose: The purpose of this study is to propose a solution to the case where $V_{50}$ calculation is impossible in the process of bulletproof test. Methods: In this study, we proposed a $V_{50}$ estimation method using logistic regression analysis. Six scenarios were applied by combining the homogeneity of the sample and the speed range. Then, 1,000 simulations were performed per scenario and six assumptions reflecting the reality were applied. Results: The result of the study, it was confirmed that there was no statistical difference between the $V_{50}$ value calculated by the conventional method and the $V_{50}$ value calculated by the improvement method. Therefore, in situations where $V_{50}$ can not be calculated, it is reasonable to use logistic regression analysis. Conclusion: This study develops a methodology that is easy to use and reliable by using statistical model based on actual data.

현대의 방탄 장갑은 우수한 관통 저항성을 갖추어야할 뿐만 아니라 군인과 군용차량의 기동성이 확보되어야 하기 때문에 경량화가 중요한 개발 요소가 되었다. 이종 적층 평판 구조의 방탄 장갑의 방탄 성능은 동일 중량 대비 구성 재료의 배열에 따라 달라진다. 본 논문에서는 케블라, 초고분자량 폴리에틸렌 그리고 에바 폼으로 구성된 방탄 장갑의 적층 배열에 따른 방탄 성능을 분석한다. 구성 재료의 두께가 5mm와 6.5mm인 두 가지 경우에서 6가지 적층 배열에 대하여 7.62 × 51mm NATO 탄환의 M80 탄을 856m/s의 속도로 충돌시키는 피탄 해석을 수행하였다. 방탄 성능을 평가하기 위해 이종 적층 평판을 관통한 발사체의 잔류 속도와 잔류 에너지를 측정하였다. 시뮬레이션 결과를 통해 케블라, 초고분자량 폴리에틸렌, 에바 폼의 배열 순서를 갖는 적층 구조가 동일 중량에 대해 가장 우수한 방탄 성능을 가짐을 확인하였다.

Modern bulletproof armor must be light and have excellent penetration resistance to ensure the mobility and safety of soldiers and military vehicles. The ballistic performance of heterogeneous structures of laminated flat plates as bulletproof armor depends on the arrangement of constituent materials for the same weight. In this study, we analyze bulletproof performance according to the stacking sequence of laminated bulletproof armor composed of Kevlar, ultra-high molecular weight polyethylene, and ethylene-vinyl-acetate foam. A ballistic analysis was performed by colliding a 7.62 × 51 mm NATO cartridge's M80 bullet at a speed of 856 m/s with six lamination arrangements with constituent materials thicknesses of 5 mm and 6.5 mm. To evaluate the bulletproof performance, the residual speed and residual energy of the projectile that penetrated the heterogeneous laminated flat plates were measured. Simulation results confirmed that the laminated structure with a stacking sequence of Kevlar, ultra-high molecular weight polyethylene, and ethylene-vinyl-acetate foam had the best bulletproof performance for the same weight.