• Title/Summary/Keyword: impact bending energy

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Study on the Prediction of the Work-Energy to the Maximum Load and Impact Bending Energy from the Bending Properties (국산 소경재의 휨 성질을 이용한 충격에너지와 최대하중까지 일-에너지 예측연구)

  • Cha, Jae-Kyung
    • Journal of the Korea Furniture Society
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    • v.19 no.5
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    • pp.350-357
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    • 2008
  • This research investigates the bending properties to predict the work-energy to maximum load and impact bending energy from static bending and impact bending test. Specimens were prepared from lumber made of thinning crop-trees. Matched specimens were used for MC 12% and green moisture specimens to measure the effect of moisture content on the absorbed energy from static and impact bending tests. The bending properties such as MOE, MOR, etc. is a good predictor to investigate the work-energy and work-energy per unit volume from static bending and impact bending test. The impact bending energy is increased with increasing moisture content. However, the work to maximum load from static bending test is increasing with increasing the MC only for higher density species.

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Impact damage and residual bending strength of CFRP composite laminates involved difference of fiber stacking orientation and matrics

  • Sim, Jae-Ki;Yang, In-Young;Oh, Taek-Yul
    • Journal of the Korean Society for Precision Engineering
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    • v.10 no.4
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    • pp.152-162
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    • 1993
  • The purpose of this study is to investigate problems of residual bending strength and the impact damage experimentally when CFRP composite laminates are subjected to Foreign object damage. The specimens composed of four types of CR/EPOXY and a CF/PEEK composite laminates which involved difference of fiber stracking orientation and matrics. The result were summariged as follows : 1) It is found that both orthotropic and guasi-isotropic composite laminates are increasimg lineally between impact energy and damage delamination area. 2) Delamination devel- opment energy(mm$^{2}$J) OF cf/epoxy composite aminates is less than that of CF/PEEK. 3) When impact energy is applied to specimens within 3J, the residual strength of orthotropic is greater than guasi-isotropic composite laminates. On the other hand, it is predicted that residual bending strength of orthotropic composite laminates is less than that of quasi-isotropic when impact energy is more thaen 3J. 4) It is found in CF/PEEK that for the impact side compression, residual of bending strength versus impact energy is almost constant, while in case of impact side tension, residual bending strength is decreased rapidly near 1.2J. of impact energy due to the effect of delamination buckling.

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Impact Damge and Residual Bending Strength of CFRP Composite Laminates Subjected to Impact Loading Fracture Mechanism and Impact Damage of Orthotropy Laminated Plates (충격하중을 받는 CFRP 적층판의 충격손상과 굽힘 잔류강도 직교 이방성 적층판의 충격손상과 파과메카니즘)

  • 심재기;양인영;오택열
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.11
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    • pp.2752-2761
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    • 1993
  • The purpose of this study is to confirm the decreasing problems of residual bending strength, and the fracture machanism experimentally when CFRP composite laminates are subjected to Foreign Object Damage. Composite laminates used for this experiment are CFRP orthotropy laminated plates, which have two-interfaces [O/sub 6//sup o//90/sub 6//sup o/]sub sym/ and four-interfaces [O/sub 3//sup o//90/sub 6//sup o//O/sub 3//sup o]/sub sym/. When the specimen is subjected to transverse impact by a steel ball, the delamination area generated by impact damage is observed by using SAM(Scanning Acoustic Microscope). also, Thefracture surfaces obtained by three-point bending test were observed by using SEM (Scanning Electron Microscope). Then, fracture mechanism was investigated based on the observed delamination area and fracture surface. The results were summarized as follows; (1) It is found that for the specimen with more interface, the critical delamination energy is increased while delamination-development energy is decreased. (2) Residual bending strength of specimen A is greater than that of Specimen B within the impact range of impact energy 1. 65J (impacted-side compression) and 1. 45J (impacted-side tension). On the other hand, when the impact energy is beyond the above ranges, residual bending strength of specimen A is smaller than that of specimen B. (3) In specimen A and B, residual strength of CFRP plates subjected to impact damage is lower in the impacted-side compression than in the impacted-side tension. (4) In the case of impacted-side compression, fracture is propagated from the transverse crack generat-ed near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension.

Effect of pre-bending on the properties of impact damage in CFRP laminates (CFRP적층판의 충격손상특성 및 손상거동에 미치는 초기굽힘의 영향)

  • 신형섭;서창민;황남성
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.5
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    • pp.1144-1149
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    • 1994
  • Damage caused in CFRP laminates by low energy impact of steel ball are investigated ultrasonically. Two types of laminated specimens having different stacking sequence are used as a target material. The effects of pre-bending on the behaviors of impact damage are specifically discussed. The initiation and progagation behaviors of delamination were largely dependent upon the bending rigidity of each specimen. Specimen C having higher bending rigidity produced larger delamination damage than the Specimen D having relatively low bending rigidity, however it was little for the Specimen C. Application of pre-bending increased the apparent bending rigidity of target during impacting, it produced delamination at lower impact energy level compared to the case of no preload.

Impact Energy Absorption Mechanism of Largely Deformable Composites with Different Reinforcing Structures

  • Kang, Tae-Jin;Kim, Cheol
    • Fibers and Polymers
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    • v.1 no.1
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    • pp.45-54
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    • 2000
  • Impact behaviors of the large deformable composites of Kevlar fiber reinforced composites of different preform structures have been investigated. An analytic tool was developed to characterize the impact behavior of the Kevlar composites. The image analysis technique, and deply technique were employed to develop energy balance equation under impact loading. An energy method was employed to establish the impact energy absorption mechanism of Kevlar multiaxial warp knitted composites. The total impact energy was classified into four categories including delamination energy, membrane energy, bending energy and rebounding energy under low velocity impact. Membrane and bending energy were calculated from the image analysis of the deformed shape of impacted specimen and delamination energy was calculated using the deplying technique. Also, the impact behavior of Kevlar composites under high velocity impact of full penetration of the composite specimen was studied. The energy absorption mechanisms under high velocity impact were modelled and the absorbed energy was classified into global deformation energy, shear-out energy, deformation energy and fiber breakage energy. The total energy obtained from the model corresponded reasonably well with the experimental results.

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The Effects of Temperature Change on the Bending Strength of CF/PEEK Laminates after Impact (온도변화가 CF/PEEK 적층재의 충격 후 굽힘강도에 미치는 영향)

  • 양인영;정종안;나승우
    • Journal of the Korean Society of Safety
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    • v.18 no.2
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    • pp.34-39
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    • 2003
  • In this paper, when CF/PEEK laminates for high efficiency space structure are subjected to FOD(Foreign Object Damage), the effects of temperature change on the impact damages(interlaminar separation and transverse crack) of CF/PEEK laminates and the relationship between residual lift and impact damages are experimentally investigated. Composite laminates used in this experiment are CF/PEEK orthotropic laminated plates, which have two-interlaces [$0^{\circ}_4/90^{\circ}_8/0^{\circ}_4$]. A steel ball launched by the air gun collides against CF/PEEK laminates to generate impact damages. And then CF/PEEK specimens with impact damages are observed by a scanning acoustic microscope under room and high temperatures. In this experimental results, various relations are experimentally observed including the delamination area vs. temperature change, the bending strength vs. impact energy and the residual bending strength vs. impact damage of CF/PEEK laminates.

Assessment of dynamic crushing and energy absorption characteristics of thin-walled cylinders due to axial and oblique impact load

  • Baaskaran, N.;Ponappa, K.;Shankar, S.
    • Steel and Composite Structures
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    • v.28 no.2
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    • pp.179-194
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    • 2018
  • Reliable and accurate method of computationally aided design processes of advanced thin walled structures in automotive industries are much essential for the efficient usage of smart materials, that possess higher energy absorption in dynamic compression loading. In this paper, most versatile components i.e., thin walled crash tubes with different geometrical profiles are introduced in view of mitigating the impact of varying cross section in crash behavior and energy absorption characteristics. Apart from the geometrical parameters such as length, diameter and thickness, the non-dimensionalized parameters of average forces which control the plastic bending moment for varying thickness has explored in view of quantifying its impact on the crashworthiness of the structure. The explicit finite element code ABAQUS is utilized to conduct the numerical studies to examine the effect of parametric modifications in crash behavior and energy absorption. Also the simulation results are experimentally validated. It is evident that the circular cross-sectional tubes are preferable as high collision impact shock absorbers due to their ability in withstanding axial and oblique impact loads effectively. Furthermore, the specific energy absorption (SEA), crash force efficiency (CFE), plastic bending moment, peak force responses and its impact for optimally tailoring a design to cater the crashworthiness requirements are investigated. The primary outcome of the study is to provide sufficient information on circular tubes for the use of energy absorbers where impact oblique loading is expected.

The Effects of Temperature Change on the Residual Bending Strength of CFRP Laminates after Impact (온도변화가 CFRP 적층재의 충격후 잔류굽힘강도에 미치는 영향)

  • Ra Seung-woo;Jung Jong-an;Yang In-young
    • Journal of the Korean Society of Safety
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    • v.20 no.1 s.69
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    • pp.75-80
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    • 2005
  • In this paper, when CF/EPOXY laminates for high efficiency space structure are subjected to FOD(Foreign Object Damage), the effects of temperature change on the impact damages(inter laminar separation and transverse crack) of CF/EPOXY laminates and the relationship between residual life and impact damages ale experimentally investigated. Composite laminates used in this experiment are CF/EPOXY orthotropic laminated plates, which have two-interfaces $[0^{\circ}_6/90^{\circ}_6]S$ and four-interfaces $[0^{\circ}_3/90^{\circ}_6/0^{\circ}_3]S$. CF/EPOXY specimens with impact damages caused by a steel ball launched from the air gun were observed by the scanning acoustic microscope under room and high temperatures. In this experimental results, various relations were experimentally observed including the delamination area vs. temperature change, the bending strength vs. impact energy and the residual bending strength vs. impact damage of CF/EPOXY laminates. And as the temperature of CF/PEEK laminates increases, the delaminaion areas of impact-induced damages decrease linearly. A linear relationship between the impact energy and the delamination areas were observed. As the temperature of CF/PEEK laminates increases, the delamination areas decrease because of higher initial delaminatin damage energy.

A study on the Impact damages and residual strength of CFRP laminates to impact under high temperature (고온에서 총격을 받는 CFRP 적층재의 총격손상과 잔류강도에 관한 연구)

  • 정종안;이상호;양인영
    • Journal of the Korean Society of Safety
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    • v.11 no.3
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    • pp.44-52
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    • 1996
  • An experimental study on the effects of temperature change on the impact damages of CFRP aminates was made through an observation of the interrelations between the Impact energy vs. delamination area, the impact energy vs. residual bending strength, and the delamination area vs. the decreasing of the residual bending strength for CF/EPOXY and CF/PEEK composite laminates subjected to FOD (Foreign Object Damage) under high temperatures.

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Influence of Residual Bending Fatigue Strength on Impact Damage of CFRP Composites (CFRP 적층판의 충격손상이 잔류 굽힘 피로강도에 미치는 영향)

  • Yang, Yong Jun;Yang, In Young
    • Journal of the Korean Society of Safety
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    • v.30 no.3
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    • pp.7-12
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    • 2015
  • CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.