• Title, Summary, Keyword: Mechanics in Composite Materials

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Mechanical behavior of composite gel periodic structures with the pattern transformation

  • Hu, Jianying;He, Yuhao;Lei, Jincheng;Liu, Zishun;Swaddiwudhipong, Somsak
    • Structural Engineering and Mechanics
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    • v.50 no.5
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    • pp.605-616
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    • 2014
  • When the periodic cellular structure is loaded or swelling beyond the critical value, the structure may undergo a pattern transformation owing to the local elastic instabilities, thus leading to structural collapse and the structure changing to a new configuration. Based on this deformation-triggered pattern, we have proposed the novel composite gel materials. This designed material is a type of architectural material possessing special mechanical properties. In this study, the mechanical behavior of the composite gel periodic structure with various gel inclusions is studied further through numerical simulations. When pattern transformation occurs, it results in a different elastic relationship compared with the material at untransformed state. Based on the obtained nominal stress versus nominal strain behavior, the Poisson's ratio and corresponding deformed structure patterns, we investigate the performance of designed composite materials and the effects of the uniformly distributed gel inclusions on composite materials. A better understanding of the characteristics of these composite gel materials is a key to develop its potential applications on new soft machines.

Characterization of the mechanical behavior of PEKK polymer and C/PEKK composite materials for aeronautical applications below and above the glass transition temperature

  • Pedoto, Giuseppe;Smerdova, Olga;Grandidier, Jean-Claude;Gigliotti, Marco;Vinet, Alain
    • Advances in aircraft and spacecraft science
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    • v.7 no.6
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    • pp.475-493
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    • 2020
  • This paper is focused on the characterization of the thermomechanical properties of semicrystalline poly-ether-ether-ketone (PEKK) and of carbon fiberreinforced thermoplastic based laminated composites (C/PEKK) below and above the glass transition temperature (Tg). Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA) and tensile tests are carried out on both pure PEKK polymer and [(±45)2, +45]s C/PEKK composite samples, showing a significant similarity in behavior. The employment of a simple micromechanical model confirms that the mechanical and physical behavior of the polymer and that of the matrix in the composite are similar.

A FE2 multi-scale implementation for modeling composite materials on distributed architectures

  • Giuntoli, Guido;Aguilar, Jimmy;Vazquez, Mariano;Oller, Sergio;Houzeaux, Guillaume
    • Coupled systems mechanics
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    • v.8 no.2
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    • pp.99-109
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    • 2019
  • This work investigates the accuracy and performance of a $FE^2$ multi-scale implementation used to predict the behavior of composite materials. The equations are formulated assuming the small deformations solid mechanics approach in non-linear material models with hardening plasticity. The uniform strain boundary conditions are applied for the macro-to-micro transitions. A parallel algorithm was implemented in order to solve large engineering problems. The scheme proposed takes advantage of the domain decomposition method at the macro-scale and the coupling between each subdomain with a micro-scale model. The precision of the method is validated with a composite material problem and scalability tests are performed for showing the efficiency.

ELASTIC GUIDED WAVES IN COMPOSITE PIPES

  • Cho Younho;Lee Joon-Hyun;Lee Chong Myong;Rose Joseph L.
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.258-263
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    • 2004
  • An efficient technique for the calculation of guided wave dispersion curves in composite pipes is presented. The technique uses a forward-calculating variational calculus approach rather than the guess and iterate process required when using the more traditional partial wave superposition technique The formulation of each method is outlined and compared. The forward-calculating formulation is used to develop finite element software for dispersion curve calculation. Finally, the technique is used to calculate dispersion curves for several structures, including an isotropic bar, two multi-layer composite bars, and a composite pipe.

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Micromechanical failure analysis of composite materials subjected to biaxial and off-axis loading

  • Ahmadi, Isa
    • Structural Engineering and Mechanics
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    • v.62 no.1
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    • pp.43-54
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    • 2017
  • In this study, the failure behavior of composite material in the biaxial and off-axis loading is studied based on a computational micromechanical model. The model is developed so that the combination of mechanical and thermal loading conditions can be considered in the analysis. The modified generalized plane strain assumption of the theory of elasticity is used for formulation of the micromechanical modeling of the problem. A truly meshless method is employed to solve the governing equation and predict the distribution of micro-stresses in the selected RVE of composite. The fiber matrix interface is assumed to be perfect until the interface failure occurs. The biaxial and off-axis loading of the SiC/Ti and Kevlar/Epoxy composite is studied. The failure envelopes of SiC/Ti and Kevlar/Epoxy composite in off-axis loading, biaxial transverse-transverse and axial-transverse loading are predicted based on the micromechanical approach. Various failure criteria are considered for fiber, matrix and fiber-matrix interface. Comparison of results with the available results in the litreture shows excellent agreement with experimental studies.

Behavior of pre-cracked deep beams with composite materials repairs

  • Boumaaza, M.;Bezazi, A.;Bouchelaghem, H.;Benzennache, N.;Amziane, S.;Scarpa, F.
    • Structural Engineering and Mechanics
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    • v.63 no.5
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    • pp.575-583
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    • 2017
  • The study covers the behavior of reinforced concrete deep beams loaded under 4-point bending, failed by shear and repaired using bonding glass fiber reinforced plastics fabrics (GFRP) patches. Two rehabilitation methods have been used to highlight the influence of the composite on the ultimate strength of the beams and their failure modes. In the first series of trials the work has been focused on the reinforcement/rehabilitation of the beam by following the continuous configuration of the FRP fabric. The patch with a U-shape did not provide satisfactory results because this reinforcement strategy does not allow to increase the ultimate strength or to avoid the abrupt shear failure mode. A second methodology of rehabilitation/reinforcement has been developed in the form of SCR (Strips of Critical Region), in which the composite materials reinforcements are positioned to band the inclined cracks (shear) caused by the shear force. The results obtained by using this method lead a superior out come in terms of ultimate strength and change of the failure mode from abrupt shearing to ductile bending.

Nanomechanical properties and wear resistance of dental restorative materials

  • Karimzadeh, A.;Ayatollahi, Majid R.;Nikkhooyifar, M.;Bushroa, A.R.
    • Structural Engineering and Mechanics
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    • v.64 no.6
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    • pp.819-826
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    • 2017
  • The effects of thermocycling procedure and material shade on the mechanical properties and wear resistance of resin-based dental restorative materials are investigated. The modulus of elasticity, hardness, plasticity index and wear resistance are determined for the conventional composite, the nanohybrid composite and the nanofilled dental composites. Disc-shape samples are prepared from each material to investigate the effects of thermocycling procedure on the mechanical properties and wear resistance of different types of dental restorative materials. In this respect, a group of samples is thermocycled and the other group is stored in ambient conditions. Then nano-indentation and nano-scratch tests are performed on the samples to measure their mechanical properties and wear resistance. Results show that the A1E shade of the dental nanocomposite possesses higher modulus of elasticity and hardness values compared to the two other shades. According to the experimental results, the mean values for the modulus of elasticity and hardness of the A1E shade of the nanocomposite are 13.71 GPa and 1.08 GPa, respectively. The modulus of elasticity and hardness of the conventional dental composite increase around 30 percent in the oral environment due to the moisture and temperature changes. The wear resistance of the dental composites is also significantly affected by moisture and temperature changes in the oral conditions. It is observed that thermocycling has no significant effect on the hardness, plasticity index and wear resistance of the nanohybrid composite and the nanocomposite dental materials.

Development of Progressive Failure Analysis Method for Composite Laminates based on Puck's Failure Criterion-Damage Mechanics Coupling Theories (Puck 파손기준-손상역학 연계이론을 활용한 적층 복합재료의 점진적 파손해석기법 개발)

  • Lee, Chi-Seung;Lee, Jae-Myung
    • Journal of the Society of Naval Architects of Korea
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    • v.52 no.1
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    • pp.52-60
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    • 2015
  • In the present study, an evaluation method for progressive failure of composite laminates has been proposed based on Puck's failure criterion and damage mechanics. The initial failure (or initiation of crack/delamination) has been assessed using Puck's failure criterion, and the progressive failure (or growth of crack/delamination) has been evaluated using fiber- and matrix-dependent damage variables. Based on Puck's failure criterion-damage mechanics coupling theories, the ABAQUS user-defined subroutine UMAT has been developed in order to analyze the progressive failure of glass/carbon fiber-reinforced composite laminates efficiently. In addition, the developed subroutine has been applied to progressive failure problem of industrial composite laminates, and the analysis results has been compared to experimental results which have been already reported in publications. It was confirmed that the simulation results were coincided well with the reported composite failure results.

Evaluation of MWCNT Exposure and the Wear Characteristics of MWCNT-containing PC/ABS Composites (다중벽 탄소나노튜브를 함유한 PC/ABS 복합재의 마모 특성 및 다중벽 탄소나노튜브의 유출 평가)

  • Lee, Hyun-Woo;Kim, Kyung-Shik;Lee, Jae-Hyeok;Kim, Hyo-Sop;Kim, Jae-Ho;Oh, Dong-Hoon;Ryu, Sang-Hyo;Jang, Young-Chan;Kim, Jae-Hyun;Lee, Hak-Joo;Kim, Kwang-Seop
    • Tribology and Lubricants
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    • v.30 no.5
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    • pp.278-283
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    • 2014
  • Carbon nanotubes (CNTs) are used in various composite materials to enhance electrical, thermal and mechanical properties of composite materials. In this study, we investigate the wear characteristics of polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) blends containing multi-walled carbon nanotubes (MWCNTs). PC/ABS blends are commonly used in many industrial applications such as cellular phones and display cases and MWCNTs have been added to the PC/ABS blends to improve their electromagnetic interference shielding (EMS). We performed wear tests on PC/ABS blends containing MWCNTs under reciprocating linear sliding conditions with chrome steel balls as a counterpart material. The normal loads were 10, 30, 50, 70, 100 N, the sliding speed was 10 mm/s, the stroke length was 15 mm, and the tests lasted 900 s. The MWCNTs included in the PC/ABS blends lower the wear volume and friction coefficient of the composites. We analyzed the wear debris collected from the composites during the tests in terms of the MWCNT concentration using inductively coupled plasma optical emission spectroscopy. The results show that the quantity of MWCNTs in the debris is proportional to the concentration of MWCNTs in the composite, indicating that the exposure of the MWCNTs to environments by wear could be increased with their concentration in the composite.

Interlaminar stress behavior of laminated composite plates under Low velocity Impact (저속충격을 받는 적층복합재료 평판의 미시구조를 고려한 interlaminar stress 거동 연구)

  • Ji, Kuk-Hyun;Kim, Seung-Jo
    • Proceedings of the Korean Society For Composite Materials Conference
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    • pp.249-252
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    • 2005
  • Prediction of damage caused by low-velocity impact in laminated composite plate is an important problem faced by designers using composites. Not only the inplane stresses but also the interlaminar normal and shear stresses playa role in estimating the damage caused. The work reported here is an effort in getting better predictions of damage in composite plate using DNS approach. In the DNS model, we discretize the composite plates through separate modeling of fiber and matrix for the local microscopic analysis. Through comparison with the homogenized model. In the view of microscopic mechanics with DNS model, interlaminar stress behaviors in the inside of composite materials is investigated and compared with the results of the homogenized model which has been used in the conventional approach of impact analysis.

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