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Sergio Oller - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation of Matrix Reinforced Composite Materials Subjected to Compression Loads
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Xavier Martinez, Sergio Oller
    Abstract:

    This paper reviews the most common formulations to obtain the compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965 ) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite. Once having described the different approaches used, and the parameters on which they depend, this paper describes a new formulation capable of obtaining the compression strength of composites taking into account the fiber buckling phenomenon. This formulation uses the serial/parallel mixing theory developed by Rastellini et al. (Comput. Struct. 86(9):879–896, 2008 ) to simulate the composite, and takes advantage of knowing the mechanical performance of the composite constituents to simulate the fiber buckling phenomenon. This is done with an homogenization procedure. It consists in introducing the interaction between fibers and matrix into their respective constitutive equations. The interaction between fiber and matrix takes into account fiber initial misalignments, its volumetric participation and the mechanical properties of both constituents. The new formulation proposed is implemented in a finite element code, taking into account that fibers can have different misalignment levels, and that the composite behaves differently if it is under tensile or compression forces. The mechanical performance of the formulation proposed is studied with several finite element simulations of compressed composites. Finally, the correctness of the formulation is proved by comparing the numerical results with the experimental tests provided by Barbero and Tomblin (Int. J. Solids Struct. 33(29):4379–4393, 1996 ), Tomblin et al. (Int. J. Solids Struct. 34(13):1667–1679, 1997 ).

  • numerical simulation of matrix reinforced composite materials subjected to compression loads
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Xavier Martinez, Sergio Oller
    Abstract:

    This paper reviews the most common formulations to obtain the compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite.

Xavier Martinez - One of the best experts on this subject based on the ideXlab platform.

  • Numerical Simulation of Matrix Reinforced Composite Materials Subjected to Compression Loads
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Xavier Martinez, Sergio Oller
    Abstract:

    This paper reviews the most common formulations to obtain the compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965 ) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite. Once having described the different approaches used, and the parameters on which they depend, this paper describes a new formulation capable of obtaining the compression strength of composites taking into account the fiber buckling phenomenon. This formulation uses the serial/parallel mixing theory developed by Rastellini et al. (Comput. Struct. 86(9):879–896, 2008 ) to simulate the composite, and takes advantage of knowing the mechanical performance of the composite constituents to simulate the fiber buckling phenomenon. This is done with an homogenization procedure. It consists in introducing the interaction between fibers and matrix into their respective constitutive equations. The interaction between fiber and matrix takes into account fiber initial misalignments, its volumetric participation and the mechanical properties of both constituents. The new formulation proposed is implemented in a finite element code, taking into account that fibers can have different misalignment levels, and that the composite behaves differently if it is under tensile or compression forces. The mechanical performance of the formulation proposed is studied with several finite element simulations of compressed composites. Finally, the correctness of the formulation is proved by comparing the numerical results with the experimental tests provided by Barbero and Tomblin (Int. J. Solids Struct. 33(29):4379–4393, 1996 ), Tomblin et al. (Int. J. Solids Struct. 34(13):1667–1679, 1997 ).

  • numerical simulation of matrix reinforced composite materials subjected to compression loads
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Xavier Martinez, Sergio Oller
    Abstract:

    This paper reviews the most common formulations to obtain the compression strength of long fiber composites due to fiber buckling. This failure mode was first studied by Rosen (Fibre Composite Materials, pp. 37–45, 1965) who defined two different fiber buckling modes, extensional and transverse. Further studies improved the first model proposed by Rosen by defining with more accuracy the mechanics of the problem. Although each formulation use a different approach to solve the problem, all of them agree in the dependence of fiber buckling on three main parameters: matrix shear strength, fiber initial misalignments and volumetric participation of the fibers in the composite.

Marcel Poulain - One of the best experts on this subject based on the ideXlab platform.

  • Aging and strength improvement of silica optical fibers
    2008
    Co-Authors: Rochdi El Abdi, Alexandru Rujnski, Marcel Poulain, Irina Severin
    Abstract:

    The reliability and the expected lifetime of optical fibers used in telecommunication technologies are closely related to the chemical environment action on the silica network. To ensure the long-term mechanical strength of the optical fibers, a polymer coating was applied onto the fiber surface during fiber fabrication. This external coating is vital to ensure a long fiber lifetime. Its protective action includes several functions, such as to protect glass fiber from any external damage, to limit chemical attack, in particular that of water, and finally to ensure fatigue protection and bending insensitivity. Since the mechanical strength of the fiber is controlled by its surface characteristics, we propose a new method for increasing fiber strength. Submitted to a mechanical stretching, fibers were plunged into hot water and aged for several days. Then, the fibers were removed from the water and various weights were suspended on the fiber ends. Just before the fiber rupture, the fibers were unloaded and subjected to dynamic tensile tests at different velocities. Result analysis proved that the aging in hot water increased the fiber strength. The Weibull's diagram study shows a bimodal dispersion of defects on the fiber surface and the important role of polymer coating.

  • New method for strength improvement of silica optical fibers
    Optics and Lasers in Engineering, 2008
    Co-Authors: A. Rujinsky, Irina Severin, C. Borda, Marcel Poulain
    Abstract:

    The reliability and the expected lifetime of optical fibers used in telecommunication technologies are closely related to the chemical environment action on the silica network. To ensure the long-term mechanical strength of the optical fibers, a polymer coating was applied onto the fiber surface during fiber fabrication. This external coating is vital to ensure a long optical fiber lifetime. Its protective action includes several functions, such as to protect glass fiber from any external damage, to limit chemical attack, in particular that of water, and finally to ensure fatigue protection and bending insensitivity, especially during handling and in-service installation. Since the mechanical strength of the fiber is controlled by its surface characteristics, we propose a new method for increasing fiber strength. The silica optical fibers used were 125 μm in diameter, with a 62.5 μm thick epoxy-acrylate coating. Fibers were rolled up around two similar cylinders. Using a screw, these cylinders moved away from one another and thus subjected the fibers to stretching. Submitted to this mechanical loading, the distended fibers were plunged into hot water at 65 or 85 °C and aged for several days. Then, the fibers were removed from the water and various weights were suspended on the fiber ends. Thus, the fibers were subjected to a tensile loading in static fatigue for several days. Just before fiber rupture, the fibers were unloaded and subjected to dynamic tensile tests at different velocities. Result analysis proved that the aging in hot water increased the fiber strength. The Weibull's diagram study shows a bimodal dispersion of defects on the fiber surface and the important role of polymer coating.

M. Ben Hassen - One of the best experts on this subject based on the ideXlab platform.

  • Effect of Fiber Weight Ratio and Fiber Modification on Flexural Properties of Posidonia-Polyester Composites
    Open Journal of Composite Materials, 2016
    Co-Authors: S. Zannen, Lassaad Ghali, Mohamed Taher Halimi, M. Ben Hassen
    Abstract:

    The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix reinforced with untreated and treated Posidonia fibers was fabricated under various fiber weight ratios. Results showed that the combined chemical treatment provided better mechanical properties of composites in comparison with untreated fiber. The fiber weight ratio influenced the flexural properties of composites. Indeed, a maximum value of flexural modulus was observed for 10% fiber weight ratio for composites reinforced with treated fibers. SEM photographs revealed a different fracture surface between Posidonia fibers reinforced polyester composites.

  • Effect of Fiber Weight Ratio and Fiber Modification on Flexural Properties of Posidonia-Polyester Composites
    Open Journal of Composite Materials, 2016
    Co-Authors: S. Zannen, Lassaad Ghali, Mohamed Taher Halimi, M. Ben Hassen
    Abstract:

    The main objective of this research is to study the effect of fiber weight ratio and chemical fiber modification on flexural properties of composites reinforced with Posidonia fiber. An unsaturated polyester matrix reinforced with untreated and treated Posidonia fibers was fabricated under various fiber weight ratios. Results showed that the combined chemical treatment provided better mechanical properties of composites in comparison with untreated fiber. The fiber weight ratio influenced the flexural properties of composites. Indeed, a maximum value of flexural modulus was observed for 10% fiber weight ratio for composites reinforced with treated fibers. SEM photographs revealed a different fracture surface between Posidonia fibers reinforced polyester composites.

Andrzej K Bledzki - One of the best experts on this subject based on the ideXlab platform.

  • Polypropylene biocomposites reinforced with softwood, abaca, jute, and kenaf fibers
    Industrial Crops and Products, 2015
    Co-Authors: Andrzej K Bledzki, P. Franciszczak, Z. Osman, Mohammed Elbadawi
    Abstract:

    The presented research study compares different types of common natural fibers used as a reinforcement in plastic composite industry. It contains characterization of each fiber type, its preparation method, and its chemical and physical properties. It follows from a description of the polypropylene biocomposite manufacturing process and physical properties of the obtained biocomposite materials. The biocomposites were manufactured in the same way and have the same matrix-to-fibre content (60/40. wt%). Therefore, the particular physical and chemical properties of the fibers used as a reinforcement and their influence onto mechanical properties of their biocomposites can be evaluated. This approach provides practical tools of how to tailor the properties of PP biocomposites by simply choosing an adequate fiber type as a matrix reinforcement. Furthermore, the information regarding: cultivation, price, and availability are compared to give a holistic view for these most common natural fibers for technical applications in plastic industry.

  • microcellular injection molded wood fiber pp composites part ii effect of wood fiber length and content on cell morphology and physico mechanical properties
    Journal of Cellular Plastics, 2006
    Co-Authors: Andrzej K Bledzki, Omar Faruk
    Abstract:

    Microcellular wood fiber reinforced PP composites, a new development using bio-fiber strengthened plastic, are prepared in an injection molding process. The microcellular composites with five different types of wood fibers (hard wood fiber, finer hard wood fiber, soft wood fiber, finer soft wood fiber, and long wood fiber) are examined. The influence of wood fiber content (30-60% by weight) on the microcellular properties is also investigated. Microcell morphology (cell size, shape, and distribution) is observed using optical light and scanning electron micrographs (SEMs). The wood fiber length, geometry, and content strongly affected the microcellular structures of wood-PP composites. Composites with finer wood fibers possess better microcellular structures, and at a constant chemical foaming content, the higher percentage of wood fiber results in composites with smaller microcells. Due to the finer microcellular structures, finer wood fibers also result in improved physico-mechanical properties.