- Email: [email protected]
Thermal diffusivity and conductivity of a carbon fibre reinformed borosilicate glass
Iitera
re
r
V Iiterature sutvey
Prepared by M. E. Adams, L. Boniface and T. Nensi
CEMENT MA TRICES Flexural strength of steel fibre-reinforced cement composites Mangat, P. S. and Gurusamy, K. Journal of Materials Science Vol 22 No 9 (September 1987) pp 3103-3110 The authors consider the applicability of two approaches to the prediction of the flexural behaviour of steel fibre-reinforced cement (SFRC). They present a modified analysis which takes into account the matrix strength based on observed failure mechanisms in a variety of practical SFRCs of different mix proportions and curing conditions. This also deals with the shift in the neutral axis at ultimate strength, the fibre/matrix bond strength and fibre orientation. The treatment of mixes containing pulverized fuel ash requires modifications to the analysis.
temperature may account for embrittlement of the material in elevated temperature aerobic environments. Thermal diffusivity and conductivity of a carbon fibre reinformed borosilicate glass Johnson, L. F., Hasselman, D. P. H. and Minford, E. Journal of Materials Science Vol 22 No 9 (September 1987) pp 3111-3117 Heat conduction characteristics of a glass reinforced with discontinuous carbon fibres are measured parallel and perpendicular to the plane of the fibre mat and compared with values for the matrix material. The temperature dependence of the thermal diffusivity is small for the matrix and the composite; the temperature dependence of the thermal conductivity follows that of the specific heat. The diffusivity decreases permanently above 600°C due to separation at the fibre/matrix interface as elastically bent fibres relax by flow in the viscous matrix at high temperature.
GENERAL
Structure and chemistry of fibre-matrix interfaces in silicon carbide fibre-reinforced glass-ceramic composites: an electron microscope study Cooper, R. F. and Chyung, K. Journal of Materials Science Vol 22 No 9 (September 1987) pp 3148-3160 Thin foils from composites containing continuous SiC fibres in glass and glass-ceramic matrices are examined using high resolution TEM and analytical scanning TEM. The high strength and toughness of these composites may be correlated with the presence of a graphitic reaction layer at the fibre/matrix interface. Analysis indicates that this layer is formed by a SiC oxidation reaction with the rate-limiting step being solid state diffusion of Si and oxygen down the silica activity gradient from fibre to matrix. The silicate interface layer found in foils annealed at high
170
Vibration and buckling of generally laminated composite plates with arbitrary edge conditions Baharlou, B. and Leissa, A. W. International Journal of Mechanical Sciences Vol 29 No 8 (1987) pp 545-556 Numerical results from this analysis of buckling loads and frequencies for laminates with damped, simply supported and free edges compare favourably with results from alternative analyses. Additional results are presented for previously unsolved problems.
METAL MA TRICES
CERAMIC MA TRICES Mechanical behaviour in compression loading of 2D composite materials made of carbon fabrics and a ceramic matrix Rossignol, J. Y., Quenisset, J. M., Hannache, H., Mallet, C., Naslain, R. and Christin, F. Journal of Materials Science Vol 22 No. 9 (September 1987) pp 3240-3252 Compression properties of 2D carbon-carbon/ceramic composites with different degrees of compaction arc investigated on samples prepared with the carbon fabric layers perpendicular and parallel to the loading direction. A model is proposed which relates the variation of stiffness and rupture strength to compaction and fabric direction. The stress/strain relationship for the composites is also described, taking into account the influence of densification on damage mechanism.
A stress intensity approach is used in the analysis of tensile failure in brittle-matrix composites in which unidirectional fibres with a unique fibre strength are held in place by friction. The analysis considers the stability under increasing stress of a crack which initiates from a matrix crack or from fracture of fibres bridging a crack.
On strain energy release rates for interfacial cracks in bi-material media Sun, C. T. and Jih, C. J. Engineering Fracture Mechanics Vol 28 No 1 (1987) pp 13-20 The crack closure method has been used to calculate the strain energy release rates associated with Mode I and Mode II propagation (GI and Gn) of a crack lying along the interface of two elastic bodies with different elastic properties. It is shown that G~ and Gn are not well defined due to the presence of oscillatory terms. However, the total strain energy release rate (G) had a convergence value and, if oscillatory terms were neglected, G~ = Gn = VzG. Using finite element methods in conjunction with the crack closure integral, it was found that G~ and Gn dependent on the choice of assumed crack extension. Simplified composite micromechanics for predicting microstresses Chamis, C. C. Journal of Reinforced Plastics and Composites Vol 6 (July 1987) pp 268-289 A unified set of simplied micromechanics equations are developed to predict the fibre composite microstresses in the fibre, matrix and at the interface for hygral, thermal and mechanical loading conditions. Several numerical examples are included to illustrate their use and computational effectiveness. Tensile fracture of brittle matrix composites: influence of fiber strength Marshall, D. B. and Cox, B. N. Acta Metallurgica Vol 35 No I1 (November 1987) pp. 2607-2620
Closed form constitute equations for metal matrix composites Abotu:li, J. International Journal of Engineering Sciences Vol 25 No 9 (1987) pp. 1229-1240 The author reformulates a previous continuum theory to give explicit constitutive relations which describe the behaviour of unidirectional fibre-reinforced materials of elastoplastic work-hardening constituent phases. These equations may be incorporated into a finite element program for analysis of metal-matrix composites. Role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures Shang, J. K., Tzou, J. L. and Ritchie, R. O. Metallurgical Transactions A Vol 18A (September 1987) pp. 1613-1627 Duplex ferritic-martensitic structures have been developed in AISI 1008 and 1015 mild steels to promote crack tip shielding in fatique, through crack deflection and resultant crack tip closure, without loss of strength. The role of crack tip shielding in the initiation and growth of both long (~>20mm) and small (10-10001~m) fatigue cracks was investigated. The fatigue threshold in AISI 1008 could be increased by 100% while a similar smaller increase was found for AISI 1015. It was found that the composite microstructures with the highest resistance to growth of long cracks showed the lowest resistance to crack initiation or small crack growth. This is explained by the mutual competition between extrinsic and intrinsic 'toughening' mechanisms. The increase in fatigue threshold in AISI 1008 is the highest ambient temperature threshold value reported to date for a metallic alloy.
COMPOSITES. MARCH 1988
re
r
V Iiterature sutvey
Prepared by M. E. Adams, L. Boniface and T. Nensi
CEMENT MA TRICES Flexural strength of steel fibre-reinforced cement composites Mangat, P. S. and Gurusamy, K. Journal of Materials Science Vol 22 No 9 (September 1987) pp 3103-3110 The authors consider the applicability of two approaches to the prediction of the flexural behaviour of steel fibre-reinforced cement (SFRC). They present a modified analysis which takes into account the matrix strength based on observed failure mechanisms in a variety of practical SFRCs of different mix proportions and curing conditions. This also deals with the shift in the neutral axis at ultimate strength, the fibre/matrix bond strength and fibre orientation. The treatment of mixes containing pulverized fuel ash requires modifications to the analysis.
temperature may account for embrittlement of the material in elevated temperature aerobic environments. Thermal diffusivity and conductivity of a carbon fibre reinformed borosilicate glass Johnson, L. F., Hasselman, D. P. H. and Minford, E. Journal of Materials Science Vol 22 No 9 (September 1987) pp 3111-3117 Heat conduction characteristics of a glass reinforced with discontinuous carbon fibres are measured parallel and perpendicular to the plane of the fibre mat and compared with values for the matrix material. The temperature dependence of the thermal diffusivity is small for the matrix and the composite; the temperature dependence of the thermal conductivity follows that of the specific heat. The diffusivity decreases permanently above 600°C due to separation at the fibre/matrix interface as elastically bent fibres relax by flow in the viscous matrix at high temperature.
GENERAL
Structure and chemistry of fibre-matrix interfaces in silicon carbide fibre-reinforced glass-ceramic composites: an electron microscope study Cooper, R. F. and Chyung, K. Journal of Materials Science Vol 22 No 9 (September 1987) pp 3148-3160 Thin foils from composites containing continuous SiC fibres in glass and glass-ceramic matrices are examined using high resolution TEM and analytical scanning TEM. The high strength and toughness of these composites may be correlated with the presence of a graphitic reaction layer at the fibre/matrix interface. Analysis indicates that this layer is formed by a SiC oxidation reaction with the rate-limiting step being solid state diffusion of Si and oxygen down the silica activity gradient from fibre to matrix. The silicate interface layer found in foils annealed at high
170
Vibration and buckling of generally laminated composite plates with arbitrary edge conditions Baharlou, B. and Leissa, A. W. International Journal of Mechanical Sciences Vol 29 No 8 (1987) pp 545-556 Numerical results from this analysis of buckling loads and frequencies for laminates with damped, simply supported and free edges compare favourably with results from alternative analyses. Additional results are presented for previously unsolved problems.
METAL MA TRICES
CERAMIC MA TRICES Mechanical behaviour in compression loading of 2D composite materials made of carbon fabrics and a ceramic matrix Rossignol, J. Y., Quenisset, J. M., Hannache, H., Mallet, C., Naslain, R. and Christin, F. Journal of Materials Science Vol 22 No. 9 (September 1987) pp 3240-3252 Compression properties of 2D carbon-carbon/ceramic composites with different degrees of compaction arc investigated on samples prepared with the carbon fabric layers perpendicular and parallel to the loading direction. A model is proposed which relates the variation of stiffness and rupture strength to compaction and fabric direction. The stress/strain relationship for the composites is also described, taking into account the influence of densification on damage mechanism.
A stress intensity approach is used in the analysis of tensile failure in brittle-matrix composites in which unidirectional fibres with a unique fibre strength are held in place by friction. The analysis considers the stability under increasing stress of a crack which initiates from a matrix crack or from fracture of fibres bridging a crack.
On strain energy release rates for interfacial cracks in bi-material media Sun, C. T. and Jih, C. J. Engineering Fracture Mechanics Vol 28 No 1 (1987) pp 13-20 The crack closure method has been used to calculate the strain energy release rates associated with Mode I and Mode II propagation (GI and Gn) of a crack lying along the interface of two elastic bodies with different elastic properties. It is shown that G~ and Gn are not well defined due to the presence of oscillatory terms. However, the total strain energy release rate (G) had a convergence value and, if oscillatory terms were neglected, G~ = Gn = VzG. Using finite element methods in conjunction with the crack closure integral, it was found that G~ and Gn dependent on the choice of assumed crack extension. Simplified composite micromechanics for predicting microstresses Chamis, C. C. Journal of Reinforced Plastics and Composites Vol 6 (July 1987) pp 268-289 A unified set of simplied micromechanics equations are developed to predict the fibre composite microstresses in the fibre, matrix and at the interface for hygral, thermal and mechanical loading conditions. Several numerical examples are included to illustrate their use and computational effectiveness. Tensile fracture of brittle matrix composites: influence of fiber strength Marshall, D. B. and Cox, B. N. Acta Metallurgica Vol 35 No I1 (November 1987) pp. 2607-2620
Closed form constitute equations for metal matrix composites Abotu:li, J. International Journal of Engineering Sciences Vol 25 No 9 (1987) pp. 1229-1240 The author reformulates a previous continuum theory to give explicit constitutive relations which describe the behaviour of unidirectional fibre-reinforced materials of elastoplastic work-hardening constituent phases. These equations may be incorporated into a finite element program for analysis of metal-matrix composites. Role of crack tip shielding in the initiation and growth of long and small fatigue cracks in composite microstructures Shang, J. K., Tzou, J. L. and Ritchie, R. O. Metallurgical Transactions A Vol 18A (September 1987) pp. 1613-1627 Duplex ferritic-martensitic structures have been developed in AISI 1008 and 1015 mild steels to promote crack tip shielding in fatique, through crack deflection and resultant crack tip closure, without loss of strength. The role of crack tip shielding in the initiation and growth of both long (~>20mm) and small (10-10001~m) fatigue cracks was investigated. The fatigue threshold in AISI 1008 could be increased by 100% while a similar smaller increase was found for AISI 1015. It was found that the composite microstructures with the highest resistance to growth of long cracks showed the lowest resistance to crack initiation or small crack growth. This is explained by the mutual competition between extrinsic and intrinsic 'toughening' mechanisms. The increase in fatigue threshold in AISI 1008 is the highest ambient temperature threshold value reported to date for a metallic alloy.
COMPOSITES. MARCH 1988