• International Journal of Automotive Technology
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• 제4권4호
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• pp.203-211
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• 2003

This paper describes a method for a falling weight impact test to estimate the impact energy absorbing characteristics and impact strength of CFRP (Carbon-fiber reinforced plastics) laminate plates based on considerations of stress wave propagation theory, which were converted to measurements of load and displacement verses time. The delamination area of impacted specimens for the different ply orientations was measured with an ultrasonic C-scanner to determine the correlation between impact energy and delamination area. The energy absorbed by a quasi-isotropic specimen having four interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy of a hybrid specimen embedding GFRP (Glass-fiber reinforced plastics) layer was higher than that of normal specimens. Also, a falling weight impact tester was built to evaluate the characteristics and impact strength of CFRPs.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.210-220
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• 2001

This paper aims at the evaluation on the characterization of CFRP laminate plates using falling weight impact tester. The experimentation was conducted on several laminates of different fiber and ply orientation. A system was built for the impact strength of CFRP laminates in consideration of stress wave propagation with using drop-weight impact tester as one of impact test. Absorbed energy of orthotropic composites with using T300 fiber, which are composed of the same fiber and stacking number is higher than that or quasi-isotropic specimen over impact energy 7J, but in case or using T700 fiber, much difference does not show. Also, absorbed energy of orthotropic composites with using T300 fiber, which are composed or stacking number and orientation became more than that of T700 fiber specimen; however great change doesn't show in case of quasi-isotropic specimens. It is found that influence was confirmed between impact energy and absorbed energy as the impact energy is increased with adding the falling weight.

• 한국지진공학회논문집
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• 제22권7호
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• pp.369-378
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• 2018

Full-scale seismic retrofit of old and deteriorated masonry buildings requires a lot of cost and time. In such buildings, installing an emergency evacuation space can be considered as an alternative. In this study, requirements of the earthquake-proof table used as an emergency evacuation space for buildings hit by earthquake are investigated. Load conditions required for the table, including the impact effects due to building debris drop, are explained. To investigate the impact effects in more detail, weight drop test is performed for an prototype earthquake-proof table. In the test, the weight of the falling object and free fall height were considered as the main test parameters. The results showed that the duration of impact is very short (0.0226~0.0779sec), and thus the impact forces increase to 15.8~45.2 times the weight of the falling object. Based on these results, design considerations and performance verification criteria of the earthquake-proof table as an emergency evacuation space are given.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 추계학술발표대회 논문집
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• pp.106-109
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• 2000

Impact tester was build up to evaluate the characterization of CFRP laminate plates under the low velocity impact. The tests were conducted on several laminates of different ply orientation A system was budded for the impact strength of CFRP laminates in consideration of stress wave propagation theory using drop-weight impact tester as one of impact test. Results indicate that absorbed energy of quasi-isotropic specimen having four interfaces is higher than that of orthotropic laminates with two interfaces. Also the damage area was measured with ultrasonic C-scanner on some samples. In the specimens the relationship was linear between damaged area and absorbed energy to some degree. Absorbed energy in the specimen that ply number, interface number and fiber stacking sequences is same but having hybrid is higher than that of orthotropic laminates without hybrid.

• 한국공작기계학회논문집
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• 제10권6호
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• pp.48-56
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• 2001

In this paper, this study aims at the evaluation on the characteristics of CFRP laminate plates using a falling weight impact tester. The experiment was conducted on several laminates of different orientation. A system was built far measur- ing the impact strength of CFRP laminates in consideration of stress wave propagation theory using a falling weight impact tester. Delamination areas of impacted specimens for the different ply orientation were measured with ultrasonic C- scanner to find correlation between impact energy and delamination area. Absorbed energy of quasi-isotropic specimen having flour interfaces was higher than that of orthotropic laminates with two interfaces. The more interfaces, the greater the energy absorbed. The absorbed energy oft hybrid specimen containing a GFRP layer was higher than that of normal specimens.

• Computers and Concrete
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• 제22권1호
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• pp.123-132
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• 2018

Reinforced concrete (RC) columns which are the main vertical structural members are exposed to several static and dynamic effects such as earthquake and wind. However, impact loading that is sudden impulsive dynamic one is the most effective loading type acting on the RC columns. Impact load is a kind of impulsive dynamic load which is ignored in the design process of RC columns like other structural members. The behavior of reinforced concrete columns under impact loading is an area of research that is still not well understood; however, work in this area continues to be motivated by a broad range of applications. Examples include reinforced concrete structures designed to resist accidental loading scenarios such as falling rock impact; vehicle or ship collisions with buildings, bridges, or offshore facilities; and structures that are used in high-threat or high-hazard applications, such as military fortification structures or nuclear facilities. In this study, free weight falling test setup is developed to investigate the behavior effects on RC columns under impact loading. For this purpose, eight RC column test specimens with 1/3 scale are manufactured. While drop height and mass of the striker are constant, application point of impact loading, stirrup spacing and concrete compression strength are the experimental variables. The time-history of the impact force, the accelerations of two points and the displacement of columns were measured. The crack patterns of RC columns are also observed. In the light of experimental results, low-velocity impact behavior of RC columns were determined and interpreted. Besides, the finite element models of RC columns are generated using ABAQUS software. It is found out that proposed finite element model could be used for evaluation of dynamic responses of RC columns subjected to low-velocity impact load.

• Composites Research
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• 제17권4호
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• pp.53-60
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• 2004

본 연구에서는 1차원 파동방정식을 적용한 낙추충격시험 시스템을 제작하여 CFRP 적층판의 충격흡수특성 및 충격 강도평가를 하였으며 그 결과가 유효함을 보였다. 충격흡수에너지에 대해서는 충격에너지가 대략 6.8J이상에서는 동일한 T300 섬유와 적층배향으로 구성된 직교이방성 시험편이 의사등방성(quasi-isotropic)보다 높게 나타났으나 T700 섬유의 경우에는 크게 차이가 나타나지 않았다. 또한 동일한 T300 섬유와 적층수로 구성된 시험편이 T700섬유로 된 시험편보다 높게 나타났으나 T700 섬유의 의사등방성 시험편의 경우에는 크게 차이가 나타나지 않았다. 초음파 C-스캐너를 이용하여 내부손상영역을 관찰하여 시험편의 손상면적과 흡수에너지의 상관관계를 평가하였다. 또한 저속충격손상으로 인한 파면을 파괴메카니즘을 규명하기 위해 주사전자현미경으로 관찰하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.144-150
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• 2007

In this paper, the low velocity response of four different sandwich panels with metal and laminate composite facesheets has been investigated by conducting drop-weight impact tests using an instrumented falling-weight impact tower. Square samples of 100mm sides were subjected low-velocity impact loading using an instrumented testing machine at six energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for four different types of sandwich panels. The impact test results show that sandwich panel with composite laminate facesheet could not observe damage mode of a permanent visible indentation after impact and has a good impact damage resistance in comparison with sandwich panel with metal aluminum facesheet.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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• pp.1178-1187
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• 2008

Quality assurance for embankment compaction is one of very important procedures to guarantee high quality construction. However, only sand replacement method (KS F2312) and static plate load test (KS F2310) which are conventional and tiresome methods are used to evaluate degree of compaction at construction fields. Recently, new types of devices such as the geogauge and the light falling weight deflectometer (LFWD), the soil impact hammer (CASPFOL) and dynamic cone penetration test etc. which are able to substitute for the conventional methods are begun to use to evaluate soil stiffness. In this study, a laboratory model test was performed to evaluate correlations among test results obtained from the new devices and to assess the potential use of them. All test results have correlations with relative density and water content. Especially, the coefficients of correlation between $E_G$ from the geogauge and $K_{30'}$ from the soil impact hammer and between $E_G$ from the geogauge and $E_{LFWD}$ from LFWD are more than 0.7 but those between the results from DCP and others are less than those between $E_{G{\cdot}}$ and $K_{30'}$ and $E_G$ and $E_{LFWD}$.

• 한국지반환경공학회 논문집
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• 제22권3호
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• pp.45-51
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• 2021

고속도로 토공에서 대부분을 차지하는 성토부의 다짐도 평가는 일반적으로 평판재하시험에 의해 이루어진다. 평판재하시험은 전통적인 시험법으로 높은 신뢰성을 가지고 있지만, 반력장비를 공수해야 하고, 시험 시 개소당 약 40분의 시간이 소요됨에 따라 광활한 토공부 전체를 관리하기에는 한계가 발생할 수 있다. 한편, 국토해양부에서는 이를 극복하고자 2010년에 '포장 하부구조 다짐관리 잠정지침'에서 간편한 다짐도 평가방법 기준을 제시한 바 있다. 하지만 10년이 지난 지금까지 고속도로공사 현장에서는 활용하고 있지 못하고 있다. 따라서, 본 연구에서는 잠정지침에서 제시한 시험법 중 충격재하 방식의 LFWD(Light Falling Weight Deflectometer)를 활용한 다짐도 평가방법에 대한 활용성을 검증하고자 하였다. 이를 위하여 현장 토질 성상 및 다짐도별로 평판재하시험 및 LFWD시험을 실시하여 상관관계를 도출하였다. 시험결과, 80% 이하의 상대 다짐도를 가진 지반에서는 시험데이타의 일관성이 없었으나, 그 이상에서 상관도가 증가하는 경향을 가지는 것을 확인할 수 있었다. 향후 충격재하 방식의 시험값의 일관성 확보를 위하여 본 연구 결과를 참고하여 시험방법 또는 시험장비를 개선한다면 토공부 다짐도 관리 사각지대를 해소하는 데에 큰 역할을 할 수 있을 것으로 기대한다.