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Applied Composite Materials: An International Journal for the Science and Application of Composite Materials (v.4, #4)
Determining the Interfacial Shear Strength in the Presence of Transcrystallinity in Composites by the ‘Single-Fibre Microcomposite Compressive Fragmentation Test‘ by Jonathan R. Wood; Gad Marom (pp. 197-207).
Based on the compressive thermal fragmentation test and model proposed recently, a transcrystalline phase grown adjacent to the surface of a high modulus carbon fibre embedded in polycarbonate was found to lower the thermal stresses in the fibre. The interfacial shear stress, calculated from the compressive stress profile generated by the model, was lowered in the presence of a transcrystalline layer. It is proposed that the transcrystalline layer reduces the radial stresses acting on the fibre, thereby reducing the friction component of the interfacial bond strength.
Keywords: transcrystanninity; microcomposites; fragmentation; thermal stresses; interfacial shear strength
Determining the interfacial shear strength in the presence of transcrystallinity in composites by the ‘single-fibre microcomposite compressive fragmentation test’ by Jonathan R. Wood; Gad Marom (pp. 197-207).
Based on the compressive thermal fragmentation test and model proposed recently, a transcrystalline phase grown adjacent to the surface of a high modulus carbon fibre embedded in polycarbonate was found to lower the thermal stresses in the fibre. The interfacial shear stress, calculated from the compressive stress profile generated by the model, was lowered in the presence of a transcrystalline layer. It is proposed that the transcrystalline layer reduces the radial stresses acting on the fibre, thereby reducing the friction component of the interfacial bond strength.
Keywords: transcrystanninity; microcomposites; fragmentation; thermal stresses; interfacial shear strength
Interfacial Effects on the Dynamic Mechanical Behavior of Weft-Knitted Glass Fiber Fabric-Reinforced Polypropylene Composites Produced of Commingled Yarns. Tensile and Flexural Response by J. Karger-Kocsis; T. Czigány (pp. 209-218).
Weft knitted glass fiber (GF) fabric-reinforced polypropylene (PP) composite sheets were produced by hot pressing of knit layers composed of a commingled yarn with a GF content of 70 wt.%(≉45 vol.%). The effects of fiber/matrix adhesion and reinforcing knit-induced stiffness anisotropy were characterized by dynamic-mechanical thermoanalysis (DMTA). DMTA spectra were registered under tensile and flexural loading in both course (C) and wale (W) direction of the knit. The knit structure-related stiffness anisotropy (relation of the Young‘s moduli measured in W- and C-directions, respectively), which proved to depend also on the loading mode of the composites, were well reflected in the DMTA spectra. The detrimental effect of poor adhesion between GF and PP could be clearly resolved when specimens cut in the C-direction were investigated. This seems to be in analogy with the transverse mechanical response of undirectional (UD) fiber-reinforced composites with interfacial variations. It was suggested that the heating-induced lofting of the composites is relied on the bond quality between GF and PP.
Keywords: commingled yarn; dynamic-mechanical thermal analysis (DMTA); interface; knitted fabric-reinforced; polypropylene (PP); stiffness anisotropy
Interfacial effects on the dynamic mechanical behavior of weft-knitted glass fiber fabric-reinforced polypropylene composites produced of commingled yarns. Tensile and flexural response by J. Karger-Kocsis; T. Czigány (pp. 209-218).
Weft knitted glass fiber (GF) fabric-reinforced polypropylene (PP) composite sheets were produced by hot pressing of knit layers composed of a commingled yarn with a GF content of 70 wt.%(≈45 vol.%). The effects of fiber/matrix adhesion and reinforcing knit-induced stiffness anisotropy were characterized by dynamic-mechanical thermoanalysis (DMTA). DMTA spectra were registered under tensile and flexural loading in both course (C) and wale (W) direction of the knit. The knit structure-related stiffness anisotropy (relation of the Young's moduli measured inW- andC-directions, respectively), which proved to depend also on the loading mode of the composites, were well reflected in the DMTA spectra. The detrimental effect of poor adhesion between GF and PP could be clearly resolved when specimens cut in theC-direction were investigated. This seems to be in analogy with the transverse mechanical response of undirectional (UD) fiber-reinforced composites with interfacial variations. It was suggested that the heating-induced lofting of the composites is relied on the bond quality between GF and PP.
Keywords: commingled yarn; dynamic-mechanical thermal analysis (DMTA); interface; knitted fabric-reinforced; polypropylene (PP); stiffness anisotropy
Modelling of the mechanical properties of composite materials at high temperatures: Part 1. Matrix and fibers by Yury Dimitrienko Dr.Sc.(Phys.&Math.) (pp. 219-237).
This paper is devoted to modelling the thermomechanical behaviour of charring composite materials at high temperatures. A multi-level model with an internal structure of unidirectional composite materials consisting of four structural levels is developed.With the help of this model, structural constitutive relations and expressions connecting elastic modules and strength characteristics of charring matrix and fibres with the properties of their internal phases are derived. Comparison of the model with experimental data for different types of matrices and fibres is conducted. Specific phenomena of the high-temperature behaviour of charring composites at high temperatures are analyzed.
Keywords: unidirectional composite; matrix; fibre; high temperatures; charring; thermo-decomposition; strength; elasticity; heat deformation; thermal degradation
Modelling of the Mechanical Properties of Composite Materials at High Temperatures: Part 1. Matrix and Fibers by Yury Dimitrienko (pp. 219-237).
This paper is devoted to modelling the thermomechanical behaviour of charring composite materials at high temperatures. A multi-level model with an internal structure of unidirectional composite materials consisting of four structural levels is developed.With the help of this model, structural constitutive relations and expressions connecting elastic modules and strength characteristics of charring matrix and fibres with the properties of their internal phases are derived. Comparison of the model with experimental data for different types of matrices and fibres is conducted. Specific phenomena of the high-temperature behaviour of charring composites at high temperatures are analyzed.
Keywords: unidirectional composite; matrix; fibre; high temperatures; charring; thermo-decomposition; strength; elasticity; heat deformation; thermal degradation
Modelling of the mechanical properties of composite materials at high temperatures: Part 2. Properties of unidirectional composites by Yury Dimitrienko Dr.Sc.(Phys.&Math.) (pp. 239-261).
In this paper, with the help of the the four-level model developed in Part 1 for charring unidirectional composites at high temperatures, the analytical relations between, on the one hand, thermo-elastic constants and thermostrength of the composite and, on the other hand, thermomechanical characteristics of its fibre and matrix are derived. It is shown that defects in the internal structure of unidirectional composites, such as misalignment and breakage of fibres, surface defects in fibres, cracking and delamination of the matrix, and also the thermal degradation of the properties of the matrix and fibres, define a thermomechanical behaviour of composites at high temperatures. Comparison of the the theoretical calculations and experimental data on thermomechanical behaviour of different polymer composites is conducted.
Keywords: unidirectional composite; high temperature; charring; thermo-decomposition; strength; elasticity; heat deformation; thermal degradation
Modelling of the Mechanical Properties of Composite Materials at High Temperatures: Part 2. Properties of Unidirectional Composites by Yury Dimitrienko (pp. 239-261).
In this paper, with the help of the the four-level model developed in Part 1 for charring unidirectional composites at high temperatures, the analytical relations between, on the one hand, thermo-elastic constants and thermostrength of the composite and, on the other hand, thermo-mechanical characteristics of its fibre and matrix are derived. It is shown that defects in the internal structure of unidirectional composites, such as misalignment and breakage of fibres, surface defects in fibres, cracking and delamination of the matrix, and also the thermal degradation of the properties of the matrix and fibres, define a thermomechanical behaviour of composites at high temperatures. Comparison of the theoretical calculations and experimental data on thermomechanical behaviour of different polymer composites is conducted.
Keywords: unidirectional composite; high temperature; charring; thermo-decomposition; strength; elasticity; heat deformation; thermal degradation