• Title, Summary, Keyword: low velocity impact load

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Damage of scarf-repaired composite laminates subjected to low-velocity impacts

  • Cheng, Xiaoquan;Zhao, Wenyi;Liu, Shufeng;Xu, Yunyan;Bao, Jianwen
    • Steel and Composite Structures
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    • v.17 no.2
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    • pp.199-213
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    • 2014
  • The damage characters of scarf repaired composite laminates subjected to low-velocity impact with various energy levels at different locations are studied experimentally. The results are compared with those of the original laminates which have no initial damage and don't need repair. The impact load-time history of the specimens, the velocity-time curves of the impactor, the post impact compressive strength of the specimens and the C-scan photographs of the damaged regions are obtained. The delamination threshold load and damage character of the specimen section at impact point are also studied. The results have shown that the impact response of a repaired composite laminate is sensitive to the location of the impact. The impact load and the delamination threshold load have shown different characters for specimens with different impact locations. The debonding characters of the adhesive and compressive strength after impact of the specimens are also influenced by impact locations.

The effects of stacking sequence on the penetration-resistant behaviors of T800 carbon fiber composite plates under low-velocity impact loading

  • Ahmad, Furqan;Hong, Jung-Wuk;Choi, Heung Soap;Park, Soo-Jin;Park, Myung Kyun
    • Carbon letters
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    • v.16 no.2
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    • pp.107-115
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    • 2015
  • Impact damages induced by a low-velocity impact load on carbon fiber reinforced polymer (CFRP) composite plates fabricated with various stacking sequences were studied experimentally. The impact responses of the CFRP composite plates were significantly affected by the laminate stacking sequences. Three types of specimens, specifically quasi-isotropic, unidirectional, and cross-ply, were tested by a constant impact carrying the same impact energy level. An impact load of 3.44 kg, corresponding to 23.62 J, was applied to the center of each plate supported at the boundaries. The unidirectional composite plate showed the worst impact resistance and broke completely into two parts; this was followed by the quasi-isotropic lay-up plate that was perforated by the impact. The cross-ply composite plate exhibited the best resistance to the low-velocity impact load; in this case, the impactor bounced back. Impact parameters such as the peak impact force and absorbed energy were evaluated and compared for the impact resistant characterization of the composites made by different stacking sequences.

Damage of Composite Laminates by Low-Velocity Impact (저속충격에 의한 복합재료 적층판의 손상)

  • Nam, Ki-Woo;Ahn, Seok-Hwan
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.284-288
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    • 2003
  • This study was investigated the nondestructive characteristics of the damage caused by low-velocity impact on symmetric cross-ply laminates. These laminates were $[0^{\circ}/90^{\circ}]{_{16s,}}\;{_{24s,}}\;{_{32s,}}\;{_{48s}}$, that is, the thickness was 2, 3, 4 and 6 mm. The impact machine, model 8250 Dynatup Instron, was used a drop-weight type with gravity. The impact velocities used in experiment were 0.75, 0.90, 1.05, 1.20 and 1.35 m/sec. The load and deformation were increased as impact velocity increase. Even if the load increased with laminates thickness in same impact velocity, the deformation decreased. The extensional velocity was a quick as laminate thickness increase in same impact velocity and as impact velocity increase in same laminate thickness. In ultrasonic scans, damaged area was represented an dimmed zone. This is due to the fact that the wave, after having been partially reflected by the defects, has not enough energy to tough the oposite side or to come back from it. The damaged laminate areas were different according to the laminate thickness and the impact velocity. The extensional velocities became lower in if direction and higher in $0^{\circ}$ direction when the size of the defects increases. But, it was difficult to draw any conclusion for the extensional velocities in $45^{\circ}$ direction.

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A Study on the Delamination Growth in Composite Laminates Subjected to Low-Velocity Impact (저속 충격을 받는 복합 재료 적층판의 층간 분리 성장에 관한 연구)

  • 장창두;송하철;김호경;허기선;정종진
    • Journal of Ocean Engineering and Technology
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    • v.16 no.6
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    • pp.55-59
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    • 2002
  • Delamination means that cracking occurs on the interface layer between composite laminates. In this paper, to predict the delamination growth in composite laminates subjected to low-velocity impact, the unit load method was introduced, and an eighteen-node 3-D finite element analysis, based on assumed strain mixed formulation, was conducted. Strain energy release rate, necessary to determine the delamination growth, was calculated by using the virtual crack closure technique. The unit load method saves the computation time more than the re-meshing method. The virtual crack closure technique enables the strain energy release rate to be easily calculated, because information of the singular stress field near the crack tip is not required. Hence, the delamination growth in composite laminates that are subjected to low-velocity impact can be efficiently predicted using the above-mentioned methods.

Low-Velocity Impact Response and Damage Analysis of Composite Laminates Under Initial In-plane Loading (초기 면내하중을 받는 복합적층판의 저속충격거동 및 손상해석)

  • Choi, Ik-Hyeon
    • Composites Research
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    • v.22 no.1
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    • pp.1-8
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    • 2009
  • In this paper low-velocity impact response and damage of composite laminates is analytically investigated. A modified displacement field of plate considering initially loaded in-plane strain is proposed. From the displacement field a finite element equation on structural behavior of composite laminate is newly induced and a computational program is coded. Numerical results using the FEM code is compared with the numerical ones from reference. Additional numerical analysis is performed on another impact condition and effect of initial in-plane load is reviewed. Potential delamination damage area in the first inter-ply surface from bottom of laminate is approximated and effect of initial in-plane load and impact condition is also reviewed.

Damage of Composite Laminates by Low-Velocity Impact (저속충격에 의한 복합재료 적층판의 손상)

  • AHN SEOK-HWAN;KIM JIN-WOOK;DO JAE-YOON;KIM HYUN-SOO;NAM KI-WOO
    • Journal of Ocean Engineering and Technology
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    • v.19 no.1
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    • pp.39-43
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    • 2005
  • The study investigated the nondestructive characteristics of damage, caused by law-velocity impact, on symmetric cross-ply laminates, composed of [0o/90o]16s, 24s, 32s, 48s. The thickness of the laminates was 2, 3, 4 and 6 mm, respectively. The impact machine used, Model 8250 Dynatup Instron, was a drop-weight type that employed gravity. The impact velocities used in this experiment were 0.75, 0.90, 1.05, 1.20 and 1.35 m/sec, respectively. Both the load and the deformation increased when the impact velocity was increased. Further, when the load increased with the laminate thickness in the same impact velocity, the deformation still decreased. The extensional velocity was quick, as the laminate thickness increased in the same impact velocity and the impact velocity increased in the same laminate thickness. In the ultrasonic scans, the damaged area represented a dimmed zone. This is due to the fact that the wave, after the partial reflection by the deflects, does not have enough energy to touch the opposite side or to come back from it. The damaged laminate areas differed, according to the laminate thickness and the impact velocity. The extensional velocities are lower in the 0o direction and higher in the 90o direction, when the size of the defect increases. However, it was difficult to draw any conclusion for the extensional velocities in the 45o direction.

Analysis of Elasto-Plastic Dynamic Behaviour of Plate Subjected to Load by Low Velocity Impact (저속충격 하중을 받는 판의 탄소성 동적거동 해석)

  • Huh, Gyoung-Jae;Dokko, Wook
    • Journal of the Korean Society for Precision Engineering
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    • v.17 no.11
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    • pp.158-164
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    • 2000
  • In this study a computer program is developed for analyzing the elasto-plastic dynamic behaviors of the plate subjected to line-loading by a low-velocity impactor. The equilibrium equation associated with the Hertzian contact law is formulated to evaluate the transient dynamic behaviour of the impacted plate. Compared with an elastic analysis, the effects of material plasticity are presented. Consequently, in the case of elasto-plastic analysys, impulse decreases, displacements increase and contact time duration is longer than the elastic case for same finite element model. And the time variation of the impacting load is not significant due to the plasticity except at the beginning of impact duration, and the induced stresses of the plate are more realistic.

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Modeling of Low Velocity Impact Damage in Laminated Composites (라미네이트 복합재 판의 저속 충격 손상 모델링)

  • Kong, Chang-Duk;Lee, Joung-Whan;C., Soutis
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.240-244
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    • 2005
  • In this study a simple model is developed that predicts impact damage in a composite laminate using an analytical model. The model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that occurred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

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Modelling of Low Velocity Impact Damage In Laminated Composites

  • Lee Jounghwan;Kong Changduk;Soutis Costas
    • Journal of Mechanical Science and Technology
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    • v.19 no.4
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    • pp.947-957
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    • 2005
  • In this study a simple model is developed that predicts impact damage in a composite laminate avoiding the need of the time-consuming dynamic finite element method (FEM). The analytical model uses a non-linear approximation method (Rayleigh-Ritz) and the large deflection plate theory to predict the number of failed plies and damage area in a quasi-isotropic composite circular plate (axisymmetric problem) due to a point impact load at its centre. It is assumed that the deformation due to a static transverse load is similar to that oc curred in a low velocity impact. It is found that the model, despite its simplicity, is in good agreement with FEM predictions and experimental data for the deflection of the composite plate and gives a good estimate of the number of failed plies due to fibre breakage. The predicted damage zone could be used with a fracture mechanics model developed by the second investigator and co-workers to calculate the compression after impact strength of such laminates. This approach could save significant running time when compared to FEM solutions.

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.
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.129-134
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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 3mm 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) fallow the static curve well. In addition, at a given energy the peak force is in good agreement between the static and impact cases. From the CAI strength and open hole compressive strength tests, it is identified that the failure behaviour of the specimens was very similar to that observed in laminated plates with open holes under compression loading. The residual strengths are in good agreement with the measured open hole compressive strengths, considering the impact damage site as 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.

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