• 제목/요약/키워드: Composite number

검색결과 1,283건 처리시간 0.027초

복합재료 거동특성의 파괴해석 I - 이방성 소성 적합모델 (A Progressive Failure Analysis Procedure for Composite Laminates I - Anisotropic Plastic Constitutive Model)

  • 이규세
    • 복합신소재구조학회 논문집
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    • 제5권4호
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    • pp.1-10
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    • 2014
  • A progressive failure analysis procedure for composite laminates is developed in here and in the companion paper. An anisotropic plastic constitutive model for fiber-reinforced composite material, is developed, which is simple and efficient to be implemented into computer program for a predictive analysis procedure of composites. In current development of the constitutive model, an incremental elastic-plastic constitutive model is adopted to represent progressively the nonlinear material behavior of composite materials until a material failure is predicted. An anisotropic initial yield criterion is established that includes the effects of different yield strengths in each material direction, and between tension and compression. Anisotropic work-hardening model and subsequent yield surface are developed to describe material behavior beyond the initial yield under the general loading condition. The current model is implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS), and is presented in the companion paper. The accuracy and efficiency of the anisotropic plastic constitutive model are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

Dynamic reliability of structures: the example of multi-grid composite walls

  • Liu, Pei;Yaoa, Qian-Feng
    • Structural Engineering and Mechanics
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    • 제36권4호
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    • pp.463-479
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    • 2010
  • Based on damage accumulation of multi-grid composite walls, a method of dynamic reliability estimations is proposed. The multi-grid composite wall is composed of edge frame beam, edge frame columns, grid beams, grid columns and filling blocks. The equations including stiffness, shear forces at filling blocks cracking and multi-grid composite walls yielding, ultimate displacement, and damage index are obtained through tests of 13 multi-grid composite wall specimens. Employing these equations in reliability calculations, procedures of dynamic reliability estimations based on damage accumulation of multi-grid composite walls subjected to random earthquake excitations are proposed. Finally the proposed method is applied to the typical composite wall specimen subjected to random earthquake excitations which can be specified by a finite number of input random variables. The dynamic reliability estimates, when filling blocks crack under earthquakes corresponding to 63% exceedance in 50 years and when the composite wall reach limit state under earthquakes corresponding to 2-3% exceedance in 50 years, are obtained using the proposed method by taking damage indexes as thresholds. The results from the proposed method which show good agreement with those from Monte-Carlo simulations demonstrate the proposed method is effective.

Mechanical behavior of prefabricated steel-concrete composite beams considering the clustering degree of studs

  • Gao, Yanmei;Fan, Liang;Yang, Weipeng;Shi, Lu;Zhou, Dan;Wang, Ming
    • Steel and Composite Structures
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    • 제45권3호
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    • pp.425-436
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    • 2022
  • The mechanical behaviors of the prefabricated steel-concrete composite beams are usually affected by the strength and the number of shear studs. Furthermore, the discrete degree of the arrangement for shear stud clusters, being defined as the clustering degree of shear stud λ in this paper, is an important factor for the mechanical properties of composite beams, even if the shear connection degree is unchanged. This paper uses an experimental and calculation method to investigate the influence of λ on the mechanical behavior of the composite beam. Five specimens (with different λ but having the same shear connection degree) of prefabricated composite beams are designed to study the ultimate supporting capacity, deformation, slip and shearing stiffness of composite beams. Experimental results are compared with the conventional slip calculation method (based on the influence of λ) of prefabricated composite beams. The results showed that the stiffness in the elastoplastic stage is reduced when λ is greater than 0.333, while the supporting capacity of beams has little affected by the change in λ. The slip distribution along the beam length tends to be zig-zagged due to the clustering of studs, and the slip difference increases with the increase of λ.

Acoustic Emission 의 섬유파단 Source Location을 이용한 Carbon Fiber/Epoxy Composites의 계면특성 및 비파괴적 평가 (Interfacial and Nondestructive Evaluation of Single Carbon Fiber/Epoxy Composites by Fiber Fracture Source Location using Acoustic Emission)

  • Kong, Jin-Woo;Kim, Jin-Won;Park, Joung-Man;Yoon, Dong-Jin
    • 한국복합재료학회:학술대회논문집
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    • 한국복합재료학회 2001년도 추계학술발표대회 논문집
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    • pp.116-120
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    • 2001
  • Fiber fracture is one of the dominant failure phenomena to determine total mechanical properties in composites. Fiber fracture locations were measured by optical microscopic method and acoustic emission (AE) as functions of matrix toughness and surface treatment by the electrodeposition (ED), and then two methods were compared. Two AE sensors were attached on the epoxy specimen and fiber fracture signals were detected with elapsed time. The interfacial shear stress (IFSS) was measured using tensile fragmentation test and AE system. In ED-treated case, the number of the fiber fracture measured by an optical method and AE was more than that of the untreated case. The signal number measured by AE were rather smaller than the number of fragments measured by optical method, since some fiber fracture signals were lost while AE detection. However, one-to-one correspondence between the x-position location by AE and real break positions by optical method was generally established well. The fiber break source location using AE can be a valuable method to measure IFSS for semi- or nontransparent matrix composites nondestructively (NDT).

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Impact Collapse Characteristics of CF/Epoxy Composite Tubes for Light-Weights

  • Kim, Young-Nam;Hwang, Jae-Jung;Baek, Kyung-Yun;Cha, Cheon-Seok;Yang, In-Young
    • Journal of Mechanical Science and Technology
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    • 제17권1호
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    • pp.48-56
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    • 2003
  • This paper investigates the collapse characteristics of CF/Epoxy composite tubes subjected to axial loads as changing interlaminar number and outer ply orientation angle. The tubes are aften used for automobiles, aerospace vehicles, trains, ships, and elevators. We have performed static and dynamic impact collapse tests by a way of building impact test machine with vertical air compression. It is fanad that CF/Epoxy tube of the 6 interlaminar number (C-type) with 90$^{\circ}$ outer orientation angle and trigger absorbed more energy than the other tubes (A. B and D-types). Also collapse mode depended upon outer orientation angle of CF/Epoxy tubes and loading type as well; typical collapse modes of CF/Epoxy tubes are wedged, splayed and fragmentcl.

복합재 패치로 보수된 노치형 알루미늄 합금 평판의 음향방출 특성 (Acoustic Emission Characteristics of Notched Aluminum Plate Repaired with a Composite Patch)

  • 윤현성;최낙삼
    • 비파괴검사학회지
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    • 제31권1호
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    • pp.53-61
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    • 2011
  • 본 연구는 편측 노치가 삽입된 A16061-T6 알루미늄 합금 평판 시편에 대해 유리섬유강화플라스틱(GFRP) 복합재 패치의 적층수를 변수로 하여 보수히고, 인장 하중에 따른 시편의 손상 과정을 음향방출법(acoustic emission, AE)으로 실시간 분석하였다. AE 에너지 발생률(AE energy rate), hit 발생률(hit rate), AE 진폭(AE amplitude) 거통과 파형 및 1차 중심주파수(1st peak frequency)의 대역을 조사하여, 시편 파괴시 알루미늄 크랙(Al cracking), 섬유 파단(fiber breakage), 수지 균열(resin cracking), 층간 분리(delamination)로 분류하였다. 시편의 변위를 음향방출 특성에 따라 구간(region) I, II, III으로 나눌 수 있었으며, 패치 자체가 실제 파괴되는 구간인 구간 II를 세부적으로 분석하여 패치의 적층수에 따른 AE 특성 차이를 구하였다.

초고속 원심분리기 복합재 로터의 해석 및 최적설계 (Optimal Design of Ultracentrifuge Composite Rotor by Structral Analysis)

  • 박종권;김영호;하성규
    • 한국정밀공학회지
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    • 제15권1호
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    • pp.130-136
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    • 1998
  • A procedure of stress and strength analysis has been proposed for the centrifuge rotor of composite materials of quasi-isotropic laminates. The goal in this study is to maximize the allowable rotating speed, that is, to minimize maximum strength ratio with the given path length by changing the geometric parameter-outer radius and ply angles in quasi-isotropic laminates. Optimum values of the geometric parameter-outer radius and ply angles are obtained by multilevel optimization. All the geometric dimensions and stresses are normalized such that the result can be extended to a general case. Two dimensional analysis at each cross section with an elliptic tube hole subjected to internal hydrostatic pressures by samples as well as the centrifugal body forces has been performed along the height to calculate the stress distribution with the plane stress assumption, and Tsai-Wu failure criterion is used to calculate the strength ratio. The maximum allowable rotating speed can be increased by changing the radii of the outer surface along the height with the maximum strength ratio under the unit value : The optimal number of ply angles maximizing the allowable rotating speed in quasi-isotropic laminates is found to be the half number of tube hole, and the optimal laminate rotation angle is the half of $[{\pi}/m]$. A $[{\pi}/3]$ laminate, for instance, is stronger than a $[{\pi}/4]$ laminate for the centrifuge rotor of 6 tube hole number even though they have the same stiffness.

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Correlation between clinical clerkship achievement and objective structured clinical examination (OSCE) scores of graduating dental students on conservative dentistry

  • Bang, Jae-Beum;Choi, Kyoung-Kyu
    • Restorative Dentistry and Endodontics
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    • 제38권2호
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    • pp.79-84
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    • 2013
  • Objectives: This study aimed to investigate the effect of clinical clerkship-associated achievements, such as performance of procedures at the student clinic, observation, and attitude towards a clerkship, on the objective structured clinical examination (OSCE) scores of dental students graduating in restorative dentistry. Materials and Methods: The OSCEs consisted of two stations designed to assess students' clinical skills regarding cavity preparation for a class II gold inlay and a class IV composite restoration. The clerkship achievements, consisting of the number of student clinical procedures performed, observation-related OSCE, and scores of their attitudes towards a conservative dentistry clerkship, were assessed. Correlation and multiple regression analyses were conducted. Results: The correlation coefficient between the OSCE scores for cavity preparation for a class II gold restoration and clerkship attitude scores was 0.241 (p < 0.05). Regarding a class IV composite restoration, OSCE scores showed statistically significant correlations with the observation (r = 0.344, p < 0.01) and attitude (r = 0.303, p < 0.01) scores. In a multiple regression analysis, attitudes towards a clerkship (p = 0.033) was associated with the cavity preparation for a class II gold inlay OSCE scores, while the number of procedure observations (p = 0.002) was associated with the class IV composite restoration OSCE scores. Conclusions: The number of clinical procedures performed by students, which is an important requirement for graduation, showed no correlation with either of the OSCEs scores.

[Retracted]Structural performance of RC beams with openings reinforced with composite materials

  • Shaheen, Yousry B.I.;Mahmoud, Ashraf M.
    • Structural Engineering and Mechanics
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    • 제83권4호
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    • pp.475-493
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    • 2022
  • The results of research focusing on the experimental and numerical performance of ferrocement RC beams with openings reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh, and polyethylene mesh independently are presented in this article. Casting and testing of fourteen reinforced concrete beams with dimensions of 200×100×2000 mm under concentric compression loadings were part of the research program. The type of reinforcing materials, the volume fraction of reinforcement, the number of mesh layers, and the number of stirrups are the major parameters that change. The main goal is to understand the impact of using new appealing materials in reinforcing RC beams with openings. Using ANSYS-16.0 Software, nonlinear finite element analysis (NLFEA) was used to demonstrate the behavior of composite RC beams with openings. A parametric study is also conducted to discuss the variables that can have the greatest impact on the mechanical behavior of the proposed model, such as the number of openings. The obtained experimental and numerical results demonstrated the FE simulations' acceptable accuracy in estimating experimental values. Furthermore, demonstrating that the strength gained of specimens reinforced with fiber glass meshes was reduced by approximately 38% when compared to specimens reinforced with expanded or welded steel meshes is significant. In addition, when compared to welded steel meshes, using expanded steel meshes in reinforcing RC beams with openings results in a 16 percent increase in strength. In general, when ferrocement beams with openings are tested under concentric loadings, they show higher-level ultimate loads and energy-absorbing capacity than traditional RC beams.

2차 반응표면분석 모델 적합을 위한 부분합성계획에 관한 연구 (A Study on Small Composite Designs for Fitting Second Order Response Surface Models)

  • 박성현;서혁;박준오
    • 한국품질경영학회:학술대회논문집
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    • 한국품질경영학회 1998년도 The 12th Asia Quality Management Symposium* Total Quality Management for Restoring Competitiveness
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    • pp.580-593
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    • 1998
  • 2차 반응표면분석을 위한 부분합성계획은 실험 비용이 많이 들거나, 실험 자체가 어려워서 시간의 소비가 많은 경우, 실험오차의 독립추정이 가능할 때 효과적이다. 반응표면분석에서는 회전성과 기울기 회전성을 만족하는 것이 중요하다. 따라서 본 논문에서는 회전성과 기울기 회전성의 관점에서 부분합성계획을 살펴보고 또한 인자의 수와 중심점의 수가 변함에 따라서 어떤 a(중심에서 축점까지의 거리)의 값이 최적의 실험계획이 되도록 하는지를 연구하였다.

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