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phenolic resin composites. Part II: Numerical evaluation
surfaces were found to be transgranular. Under confining pressure, fracture surfaces were covered by a thin layer of glass. At the highest strain rate (0.81 sec -~) the particles produced by ambient pressure granulation were extensively slicken sided due to inter particle friction. SiC whisker reinforced Si3N 4 composites Kandorl, T., Kobayashi, S., Wada, S. and Kamigiato O. Journal o f Materials Science Letters Vol 6 (1987) pp 1356-1358 New fabrication techniques are presented which improve the properties of SiC whiskerreinforced Si3N4 ceramics. The flexural strength and fracture toughness were measured using four-point bending and the chevron notch method respectively. The matrix (Si3N 4 + 5% YzO3 + 5% MgA1204) and SiC whiskers (10%) were mixed in ethanol, dried and blended with binders for injection moulding. After injection moulding, the test pieces were dewaxed and HIP treated at temperatures ranging from 1500°1900°C, The bulk density of the composite was found to be lower than that of the monolithic Si3N,, material although the flexural strength and toughness of the composite was higher than the monolithic material. This is in contrast to previously reported findings and is shown to be due to the fabrication technique used.
GENERAL Crack tip heating in short fibre composites under fatigue loading conditions Lang, R. W. and Manson, J. A. Journal of Materials" Science Vo122 (1987) pp 3576-3580 Crack tip heating mechanisms under fatigue loading conditions have been studied. Maximum crack tip temperatures and temperature profiles along the crack plane were recorded as a function of the stress intensity factor using an infrared microscope. Values of dynamic loss compliance were also determined. The results are discussed in terms of the relative contributions of the two principle mechanisms of heating - hysteretic heating and frictional heating. Exact solutions for laminated cylindrical shells in cylindrical bending Ren, J. G. Composites Science and Technology Vo129 No 3 (1987) pp 169-187 An exact solution for an orthotropic cylindrical laminated shell with cylindrical anisotropy in cylindrical bending is presented. Numerical results are compared with corresponding results obtained using classical shell theory and Donnell shell theory. It is shown that classical theory converges to the exact solution in all problems whereas the Donnell theory does not. The classical theory exhibits larger differences with the exact solution at low curvature radius-to-depth ratios than at higher ratios. It is proposed that the exact solution may be used to study sandwich shells with orthotropic materials. An experimental and finite element investigation into the mechanical response of 0/90 pin-loaded laminates Serabian, S. M. and Oplingcr, D. W. Journal o f Composite Materials Vol 21 No 7 (July 1987) pp 631-649
COMPOSITES
. MAY 1988
Laminate mechanical properties determined from tests and laminate plate theory are used as input data for a linear elastic finite element analysis of a pin-loaded 0/90 composite plate. These predictions are compared with experimental full-field strain measurements made by the Moir6 method. The significant in-plane shear nonlinearity effect found in the 0/90 laminate under conditions of pin-loading is investigated using a nonlinear orthotropic finite element analysis. Inhomogeneity effect on the stress intensity factor Chiang, C. R. Journal o f Composite Materials Vo121 No 7 (July 1987) pp 610-618 The case considered is that of a pennyshaped crack lying perpendicular to the fibre direction in a composite loaded in uniaxial tension parallel to the fibre direction. This study aims to find the conditions under which the assumption of material homogeneity is justified in the expression for the stress intensity factor at the crack tip (K = 2P~/(a)/~) by modelling the distribution of microgeometry as a number, N, of ringshaped regions. Examples from glass/epoxy and boron/epoxy systems show that the effect of inhomogeneity can be neglected for N>~103. Therefore, the crack should be at least three orders of magnitude greater than the fibre diameter to allow the assumption of homogeneity in the calculation of K. A methodology for synthesising symmetric laminated beams with optimal elastodynamic response characteristics Sung, C. K., Thompson, B. S., Gandhi, M. U. and Lee, C. Y. International Journal o f Mechanical Sciences Vo129 No 12 (1987) pp 821-830 A generic methodology for synthesizing the manufacturing specification of symmetric laminated beams with optimal damping properties is proposed, the design parameters employed include fibre and matrix properties, their volume fraction, ply thickness, ply orientation, and the stacking sequence. Thermal conductivity of fibre/phenolic resin composites. Part h Thermal diffusivity measurements Mottram, J. T. and Taylor, R. Composites Science and Technology Vol 29 No 3 (1987) pp 189-210 The method of determining the thermal diffusivity of two composite materials: a carbon fibre (eight-harness satin weave cloth) reinforced phenolic resin; and a silica fibre (arranged to provide orthogonal threedirectional reinforcement) reinforced phenolic resin; is described and discussed. Heat capacity, density, fibre volume fraction; and sample weight and length change during diffusivity measurement were also obtained. Thermal conductivity of fibre/phenolic resin composites. Part II: Numerical evaluation Mottram, J. T. and Taylor, R. Composites Science and Technology Vol 29 No 3 (1987) pp 211-232 Models for the prediction of thermal conductivity of composites reinforced in one, two or three dimensions are reviewed and evaluated and compared with values obtained from data discussed in Part I. The rule-of-mixtures equation for parallel-to-fibre and the generalized dispersion approach of Bruggeman
for perpendicular-to-fibre conductivity were found to be the most appropriate. Using these models it is possible to predict the thermal conductivity of arbitrary fibre arrangements in phenolic resins.
METAL MA TRICES Bend strength of AIzO3-ZrO2 composites Kladnig, W. and Gritzner, G. Journal of Materials Science Letters Vol 6 (1987) pp 1235-1237 The bend strength of pressureless sintered Zr2-AI203 composite ceramic was investigated to determine the effects of the amount of stabilized and unstabilized Zr20, the sintering temperatures and the grain size of the original powders. The sintering temperature and the amount and type of ZrO2 added was found to affect the bend strength of the material. The addition of unstabilized ZrO2 increased the bend strength by a combination of phase transformation toughening and microcracking. The addition of Y203 stabilized ZrOz increased bend strength mainly by the mechanism of crack deflection aided by phase transformation toughening. Bend strength was also affected by sintering temperature, reaching a maximum at about 1640°C. Effect of porosity and alumina content on the high temperature mechanical properties of compocast aluminium alloy-alumina particulate composite Ghosh, P. K. and Ray, S. Journal of Materials Science Vo122 (1987)pp 4077-4086 The effects of volume fraction of alumina particles and porosity on the tensile properties of a compocast composite with an AI 4 weight % Mg alloy matrix have been investigated at various temperatures. The results are discussed in terms of an ultimate tensile strength at zero porosity, (Oo), and cx, a weakening factor. K20.6TiO2 whisker-reinforced aluminium composite by a powder metallurgical method Imai, T., Nishida, Y., Yamada, M., Shirayanagi, I. and Matsubara, H. Journal of Materials Science Letters Vol 6 (1987) pp 1257-1258 The fabrication of potassium titanate whisker/aluminium composite via a powder metallurgical route is studied. The material was fabricated by mixing the whiskers and pure aluminium powder in an organic solvent and extruding the dried mixture at 500-570°C. The whiskers aligned themselves along the extrusion axis and it was found that the strength of the composite was significantly improved by the addition of whiskers. SEM analysis of the fracture surfaces showed no degradation due to chemical reaction between potassium titanate and aluminium. The longitudinal electrical conductivity of metal-matrix composites at cryogenic temperature in the presence of a longitudinal magnetic field. Part I. Solution of the linearized Boltzmann equation Roig, F. S. and Schoutens, J. E. Journal of Materials Science Vol 22 (1987) pp 3749-3754 A solution of the linearized Boltzmann equation in the relaxation time approximation and in the presence of a longitudinal
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GENERAL Crack tip heating in short fibre composites under fatigue loading conditions Lang, R. W. and Manson, J. A. Journal of Materials" Science Vo122 (1987) pp 3576-3580 Crack tip heating mechanisms under fatigue loading conditions have been studied. Maximum crack tip temperatures and temperature profiles along the crack plane were recorded as a function of the stress intensity factor using an infrared microscope. Values of dynamic loss compliance were also determined. The results are discussed in terms of the relative contributions of the two principle mechanisms of heating - hysteretic heating and frictional heating. Exact solutions for laminated cylindrical shells in cylindrical bending Ren, J. G. Composites Science and Technology Vo129 No 3 (1987) pp 169-187 An exact solution for an orthotropic cylindrical laminated shell with cylindrical anisotropy in cylindrical bending is presented. Numerical results are compared with corresponding results obtained using classical shell theory and Donnell shell theory. It is shown that classical theory converges to the exact solution in all problems whereas the Donnell theory does not. The classical theory exhibits larger differences with the exact solution at low curvature radius-to-depth ratios than at higher ratios. It is proposed that the exact solution may be used to study sandwich shells with orthotropic materials. An experimental and finite element investigation into the mechanical response of 0/90 pin-loaded laminates Serabian, S. M. and Oplingcr, D. W. Journal o f Composite Materials Vol 21 No 7 (July 1987) pp 631-649
COMPOSITES
. MAY 1988
Laminate mechanical properties determined from tests and laminate plate theory are used as input data for a linear elastic finite element analysis of a pin-loaded 0/90 composite plate. These predictions are compared with experimental full-field strain measurements made by the Moir6 method. The significant in-plane shear nonlinearity effect found in the 0/90 laminate under conditions of pin-loading is investigated using a nonlinear orthotropic finite element analysis. Inhomogeneity effect on the stress intensity factor Chiang, C. R. Journal o f Composite Materials Vo121 No 7 (July 1987) pp 610-618 The case considered is that of a pennyshaped crack lying perpendicular to the fibre direction in a composite loaded in uniaxial tension parallel to the fibre direction. This study aims to find the conditions under which the assumption of material homogeneity is justified in the expression for the stress intensity factor at the crack tip (K = 2P~/(a)/~) by modelling the distribution of microgeometry as a number, N, of ringshaped regions. Examples from glass/epoxy and boron/epoxy systems show that the effect of inhomogeneity can be neglected for N>~103. Therefore, the crack should be at least three orders of magnitude greater than the fibre diameter to allow the assumption of homogeneity in the calculation of K. A methodology for synthesising symmetric laminated beams with optimal elastodynamic response characteristics Sung, C. K., Thompson, B. S., Gandhi, M. U. and Lee, C. Y. International Journal o f Mechanical Sciences Vo129 No 12 (1987) pp 821-830 A generic methodology for synthesizing the manufacturing specification of symmetric laminated beams with optimal damping properties is proposed, the design parameters employed include fibre and matrix properties, their volume fraction, ply thickness, ply orientation, and the stacking sequence. Thermal conductivity of fibre/phenolic resin composites. Part h Thermal diffusivity measurements Mottram, J. T. and Taylor, R. Composites Science and Technology Vol 29 No 3 (1987) pp 189-210 The method of determining the thermal diffusivity of two composite materials: a carbon fibre (eight-harness satin weave cloth) reinforced phenolic resin; and a silica fibre (arranged to provide orthogonal threedirectional reinforcement) reinforced phenolic resin; is described and discussed. Heat capacity, density, fibre volume fraction; and sample weight and length change during diffusivity measurement were also obtained. Thermal conductivity of fibre/phenolic resin composites. Part II: Numerical evaluation Mottram, J. T. and Taylor, R. Composites Science and Technology Vol 29 No 3 (1987) pp 211-232 Models for the prediction of thermal conductivity of composites reinforced in one, two or three dimensions are reviewed and evaluated and compared with values obtained from data discussed in Part I. The rule-of-mixtures equation for parallel-to-fibre and the generalized dispersion approach of Bruggeman
for perpendicular-to-fibre conductivity were found to be the most appropriate. Using these models it is possible to predict the thermal conductivity of arbitrary fibre arrangements in phenolic resins.
METAL MA TRICES Bend strength of AIzO3-ZrO2 composites Kladnig, W. and Gritzner, G. Journal of Materials Science Letters Vol 6 (1987) pp 1235-1237 The bend strength of pressureless sintered Zr2-AI203 composite ceramic was investigated to determine the effects of the amount of stabilized and unstabilized Zr20, the sintering temperatures and the grain size of the original powders. The sintering temperature and the amount and type of ZrO2 added was found to affect the bend strength of the material. The addition of unstabilized ZrO2 increased the bend strength by a combination of phase transformation toughening and microcracking. The addition of Y203 stabilized ZrOz increased bend strength mainly by the mechanism of crack deflection aided by phase transformation toughening. Bend strength was also affected by sintering temperature, reaching a maximum at about 1640°C. Effect of porosity and alumina content on the high temperature mechanical properties of compocast aluminium alloy-alumina particulate composite Ghosh, P. K. and Ray, S. Journal of Materials Science Vo122 (1987)pp 4077-4086 The effects of volume fraction of alumina particles and porosity on the tensile properties of a compocast composite with an AI 4 weight % Mg alloy matrix have been investigated at various temperatures. The results are discussed in terms of an ultimate tensile strength at zero porosity, (Oo), and cx, a weakening factor. K20.6TiO2 whisker-reinforced aluminium composite by a powder metallurgical method Imai, T., Nishida, Y., Yamada, M., Shirayanagi, I. and Matsubara, H. Journal of Materials Science Letters Vol 6 (1987) pp 1257-1258 The fabrication of potassium titanate whisker/aluminium composite via a powder metallurgical route is studied. The material was fabricated by mixing the whiskers and pure aluminium powder in an organic solvent and extruding the dried mixture at 500-570°C. The whiskers aligned themselves along the extrusion axis and it was found that the strength of the composite was significantly improved by the addition of whiskers. SEM analysis of the fracture surfaces showed no degradation due to chemical reaction between potassium titanate and aluminium. The longitudinal electrical conductivity of metal-matrix composites at cryogenic temperature in the presence of a longitudinal magnetic field. Part I. Solution of the linearized Boltzmann equation Roig, F. S. and Schoutens, J. E. Journal of Materials Science Vol 22 (1987) pp 3749-3754 A solution of the linearized Boltzmann equation in the relaxation time approximation and in the presence of a longitudinal
251