• Title/Summary/Keyword: 충격 후 압축시험

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Experimental Investigation on the Behaviour of CFRP Laminated Composites under Impact and Compression After Impact (CAI) (충격시 CFRP 복합재 판의 거동과 충격후 압축강도에 관한 실험적 연구)

  • Lee, J;Kong, C;Soutis C.
    • Composites Research
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    • v.16 no.4
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    • pp.66-73
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    • 2003
  • The importance of understanding the response of structural composites to impact and CAI cannot be overstated to develop analytical models for impact damage and CAI strength predictions. This paper presents experimental findings observed from quasi-static lateral load tests, low velocity impact tests. CAI strength and open hole compressive strength tests using 3 mm thick composite plates($[45/-45/0/90]_{3s}$- IM7/8552). The conclusion is drawn that damage areas for both quasi-static lateral load and impact tests are similar and the curves of several drop weight impacts with varying energy levels(between 5.4 J and 18.7 J) follow the static curve well. In addition, at a given energy the peak force is in good agreement between the static and impact cases. It is identified that the failure behaviour of the specimens from the CAI strength tests was very similar to that observed in laminated plates with open holes under compression loading. The residual strengths art: in good agreement with the measured open hole compressive strengths. considering the impact damage site area, an equivalent hole. The experimental findings suggest that simple analytical models for the prediction of impact damage area and CAI strength can be developed on the basis of the failure mechanism observed from the experimental tests.

Evaluation of Impact Damage and Residual Compression Strength after Impact of Glass/Epoxy Laminate Composites for Lightweight Bogie Frame induced by Ballast-Flying Phenomena (도상자갈 비산에 의한 경량 대차프레임 적용 유리/에폭시 적층 복합재의 충격손상 및 충격 후 잔류압축강도 평가)

  • Goo, Jun-Sung;Shin, Kwang-Bok;Kim, Jung-Suk
    • Journal of the Korean Society for Railway
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    • v.15 no.2
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    • pp.109-115
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    • 2012
  • In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

Test and Finite Element Analysis on Compression after Impact Strength for Laminated Composite Structures of Unidirectional CFRP (일방향 탄소섬유강화 플라스틱 복합재 적층구조의 충격 후 압축강도 시험 및 유한요소해석)

  • Ha, Jae-Seok
    • Composites Research
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    • v.29 no.6
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    • pp.321-327
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    • 2016
  • In this study, tests and finite element analyses were performed regarding compression after impact strength for laminated composite structures of unidirectional carbon fiber reinforced plastic widely used in structural materials. Two lay-up sequences of composite laminates were selected as test specimens and four impact energy conditions were applied respectively. Impact and compressive strength tests were conducted in accordance with ASTM standards. Impact damages in test specimens were analyzed by using non-destructive inspection method of C-Scan, and compression after impact strengths were calculated with compressive test results. Progressive failure analysis method that can progressively simulate damages and fractures of fiber/matrix/lamina/laminate level was used for impact and compressive strength analyses. All analysis results including contact force, deflection, impact damages, compressive strengths, etc. were compared to test results, and the validity of analysis method was verified.

Evaluation of Compressive Residual Strength in Composite Material Under Impact Damage (충격 손상을 받은 항공기용 복합재료의 압축잔류강도 평가)

  • Ahn, Sang Soo;Hong, Suk Woo;Koo, Jae Mean;Seok, Chang Sung
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.4
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    • pp.503-509
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    • 2013
  • Carbon fiber reinforced plastics (CFRPs), a composite material, are generally vulnerable to compressive load and impact damage in a direction perpendicular to the surface of the material. In particular, during the operation of an aircraft, impact damages caused by bird collisions or falling tools reduce the strength of the aircraft structure. In this study, after impact damages were applied to CFRP specimens with various impact energies and impactor diameters, the compressive residual strength of the impact-damaged specimen was evaluated by performing a compression test. Furthermore, a prediction model for the compressive residual strength is proposed according to the variation in the impact energy by comparing the test results.

A Study on Compressive Strength of Carbon/epoxy Composite Structure Repaired with Bonded Patches after Impact Damage (충격 손상된 카본/에폭시 복합재 구조의 패치 접착 보수 방안 적용 후 압축 강도 특성 평가)

  • Kong, Chang-Duk;Park, Hyun-Bum;Lim, Sung-Jin;Shin, Chul-Jin
    • Composites Research
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    • v.23 no.5
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    • pp.15-21
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    • 2010
  • In this study, repair and maintenance schemes of the damaged composite structure was investigated, and a repair process of the carbon/epoxy laminate composite structure was investigated numerically and experimentally. The composite laminates were damaged by drop weight type impact test machine. The damaged composite structure was repaired using external patch repair method after removing damaged area. The compressive strength test and analysis results after repairing the impact damaged specimens were compared with the compressive strength test and analysis results of undamaged specimens and impact damaged specimens. Finally, the strength recovery capability by repairing were investigated.

Impact Performance of 3D Orthogonal Composites by Automated Tape Placement Process (자동적층 공정에 의한 3차원 직교 섬유배열구조 복합재의 충격특성)

  • Song S-W;Lee C-H;Um M-K;Hwang B-S;Byun J-H
    • Composites Research
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    • v.18 no.3
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    • pp.38-46
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    • 2005
  • In order to characterize the outstanding performance of three-dimensional (3D) composites, the low velocity impact test has been carried out. 3D fiber structures have been achieved by using the automated tape placement (ATP) process and a stitching method. Materials for the ATP and the stitching process were carbon/epoxy prepreg tapes and Kevlar fibers, respectively. Two-dimensional composites with the same stacking sequence as 3D counterparts have also been fabricated for the comparison of damage tolerance. For the assessment of damage after the impact loading, specimens were subjected to C-Scan nondestructive inspection. Compression after impact (CAI) tests were conducted to evaluate residual compressive strength. The damage area of 3D composites was greatly reduced $(30-40\%)$ compared with that of 2D composites. Although the CAI strength did not show drastic improvement for 3D composites, the ratio of retained strength was $5-10\%$ higher than 2D samples. The effect of stitching on the impact performance was negligible above the energy level of 35 Joules.

Compressive Strength Restoration Evaluation of Sandwich Composite Laminates Repaired by Scarf Method (패치 보수된 샌드위치 복합재 적층판의 압축시 강도회복 평가)

  • Kim, Jung-Seok;Yoon, Hyuk-Jin;Kim, Seung-Cheol;Seo, Sung-Il
    • Journal of the Korean Society for Railway
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    • v.12 no.1
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    • pp.110-114
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    • 2009
  • This study is for the evaluation of compressive strength restoration of sandwich composite laminates with adhesively bonded scarf patches. It was used in this study that the sandwich composite laminate with an aluminum honeycomb core and CF1263 woven fabric carbon/epoxy faces was applied to the car body structure for Korean tiling train. In this study, it was damaged by low velocity impact and repaired using scarf repair method. Then, the compressive strength restoration of assessed by compressive after impact (CAI) test. From the test, it could be known that the compressive strength was restored up to 72% by only scarf repair method and 91% applied by an extra ply over the undamaged one.

Analysis of Low Velocity Impact Damage and Compressive Strength After Impact for Laminated Composites (복합재 구조물의 저속 충격 손상 및 충격 후 압축 강도 해석)

  • Suh, Young-W.;Woo, Kyeong-Sik;Choi, Ik-Hyun;Kim, Keun-Taek;Ahn, Seok-Min
    • Aerospace Engineering and Technology
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    • v.10 no.1
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    • pp.183-192
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    • 2011
  • The demand for weight saving and high performance of aircraft require the more uses of composite materials. However the complicate behaviors and various failure characteristics restrict usage of composite materials. Low-velocity impact damage is a major concern in the design of structures made of composite materials, because impact damage is hidden and cannot be detected by visual inspection. Especially, the reduction on compressive strength after impact is influenced by the ply delaminations introduced as damage by impact event. In this research, the numerical analysis was performed to investigate impact damage and compressive strength after impact. It was found that impact force history and compressive strength after impact calculated by the numerical analysis were compared and shown a good agreement with experimental results.

Low Velocity Impact Behavior of Aluminium and Glass-Fiber Honeycomb Structure (알루미늄과 유리섬유 하니컴 구조의 저속 충격 거동)

  • Kim, Jin Woo;Won, Cheon;Lee, Dong Woo;Kim, Byung Sun;Bae, Sung In;Song, Jung Il
    • Composites Research
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    • v.26 no.2
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    • pp.116-122
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    • 2013
  • In this study, impact behavior of aluminium and glass-fiber structure is studied under low impact velocity. Compression test is carried out to investigate the compressive strength of the specimens. The degree of damage is observed using microscopy and compared with the experimental analysis data. The maximum load capacity, impact strength and elastic energy of glass-fiber honeycomb sandwich panel are more than the aluminium honeycomb sandwich panel.

Acoustic Emission Monitoring of Compression-after-Impact Test of Nano-Particles-Coated CFRP Damaged by Simulated Lightning Strikes (나노입자 코팅 CFRP의 모의 낙뢰 충격손상 후 압축시험에서의 음향방출 거동)

  • Shin, Jae-Ha;Kwon, Oh-Yang;Seo, Seong-Wook
    • Journal of the Korean Society for Nondestructive Testing
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    • v.31 no.1
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    • pp.62-67
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    • 2011
  • Nanoparticles-coated and impact-damaged carbon-fiber reinforced plastics(CFRP) laminates were tested under compression-after-impact(CAI) mode and the propagation of damage due to compressive loading has been monitored by acoustic emission(AE). The impact damage was induced not by mechanical loading but by a simulated lightning strike. CFRP laminates were made of carbon prepregs prepared by coating of conductive nano-particles directly on the fibers and the coupons were subjected to simulated lightning strikes with a high voltage/current impulse of 10~40 kA within a few microseconds. The effects of nano-particles coating and the degree of damage induced by the simulated lightning strikes on the AE activities were examined, and the relationship between the compressive residual strength and AE behavior has been evaluated in terms of AE event counts and the onset of AE activity with the compressive loading. The degree of impact damage was also measured in terms of damage area by using ultrasonic C-scan images. From the results assessed during the CAI tests of damaged CFRP showed that AE monitoring appeared to be very useful to differentiate the degree of damage hence the mechanical integrity of composite structures damaged by lightning strikes.