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A statistical theory of material strength with application to composite materials
extruding plasticized powders and sintering. Both oxides were modified b y adding small quantities of MgO and TiO2 to enhance sintering and the ZrO2 was stabilized b y adding CaO. With a variety of plasticizers, fibres of 0-5 - 0 . 6 m m diameter were extruded and sintered at 1 650°C. With porosities of about 25%, the A1203 attained an UTS of 2 2 0 - - 3 0 0 k g / m m 2 and the ZrO2 1 0 0 - 200kg/mm 2. (70/1/60)
Mechanical and microscopical investigation of SiC whiskers OP HET VELD, A. J. G. and VELDKAMP, J. D. E. Fibre Science and Technology, Vol 2, No 4, p 269 (April 1970) Measurements of r o o m temperature tensile strength and Young's modulus of hair-like whiskers of SiC grown by a vapour liquid-solid method and of ribbon like whiskers grown by the Lely process are reported. Amongst the conclusions are that a tapered whisker is unlikely to have one Young's modulus, holes in the core o f the hair-like whiskers markedly lower stiffness and strength and that the stress concentrating factor of defects can probably be reduced by a surface layer of SiO2 obtained during preparation. (70/1/61)
Fracture of bone PIEKARSKI, K. J o f Applied Physics, Vo141, No 1, pp 215 - 223 (January 1970) The energy required to propogate a fracture through bone was studied using an Instron machine. Metallographic and scanning electron microscope techniques were used to observe the fracture mechanism. At low strain rates bone appears to be a tough material, but fracture in a more brittle mode occurs at high strain rates. Pullout o f b o t h the large scale fibre structure (esteons) and very much smaller fibrils (probably mineral crystallites) was observed in slow fractures. The presence of discontinuities such as blood vessels tends to enhance rather than reduce the toughness of bone. (70/1/62)
cost means that the lead of the British Coal Utilization Research Association is producing carbon fibre at an expected price of £1/lb should be followed up without delay. After the solvent treatment of coal and distillation, the remaining product, coal extract, is used for the manufacture of carbon fibre, polymer and specialist and electrode coke and it is concluded that cheap carbon fibre such as this could benefit many research applications of carbon fibres which at the moment are stifled by its high cost. (70/1]63)
Whisker sorter is key to high strength composites. PETERS, D.
The Engineer, p 22 (April 1970) The Explosives Research and Development Establishment and Glass Developments Ltd have produced a classification technique suitable for all types of whisker. A suspension of the fibres is fed onto a rotating cylindrical screen and as it drains through the long fibres are retained and subsequently removed by water or air jets. A complete set of rotary screens is available from 160 wires/cm to 1-25. A complete fibre classification unit as installed by Lonza Ltd of Switzerland is shown schematically. (70/1/64)
The tensile behaviour of fibrous materials at high rates of strain and subambient temperatures SKELTON, J. Mat Res and Standards, Vol 10, No 6, pp 20 - 25 (June 1970) Man-made textile fibres, glass fibres and metal fibres, all potential reinforcing materials, have been tested in the strain-rate range 1 - 14 000%/s and the subambient temperature range 70°F to - 3 2 0 ° F . Data on elongation r u p t u r e - stress, tenacity and initial modulus are presented for the 5 fibretypes. A detailed description of the test methods used is also given. (70/1/65)
Carbon fibre from coal - w h i c h is not for burning PETERS, D. The Engineer, Vol231, No 5971, p 30 (July 1970)
Interfacial tractions in a fibrereinforced elastic composite material SMITH, G. E. and SPENCER, A. J. M. J o f Mech and Physics o f Solids, Vol 18, No 2 (April 1970)
The application of carbon fibres to the more exotic fields in view of their high
A mathematical analysis of the problem of the forces acting over the
324
COMPOSITESSeptember 1970
fibre-matrix interface and the conditions governing fracture of that interface. The composite is regarded as consisting of circular cylindrical elements and solutions are obtained for stress and displacement of a typical element under boundary conditions which approximate to those of an element in the interior of the composite. It is shown that large shear stresses can occur near the ends of the element, which may tend to break the interracial bond. (70/1/66)
Mesure statique de Module D'Young de fibres VERCHERY, G. Fibre Science and Technology, Vol 2, No 4, p 283 (April 1970) The theory and practical method of measuring the static Young's Modulus of fibres of tungsten, boron and silicon carbide are given and the results of both are compared. The principal source o f error is said to be the measurement of fibre diameter which occurs as the term d-4 in the expression for the static Young's Modulus. The moduli of refractory fibres are found to be in agreement with those measured dynamically and those reported in the literature. (7011/67).
Variational bounds of transport properties of composite materials YEH, R. H. T. J of Applied Physics, Vol 41, No 1, pp 224 - 226 (January 1970) The electrical properties of composite materials are treated theoretically. Relative merits, physical interpretations, limitations and generalisations o f various bounds applied to composites are discussed. (70/1/68)
A statistical theory of material strength with application to composite materials ZWEBEN, C. and ROSEN, B. W. J o f the Mech Physics of Solids, Vol 18, No 3, pp 189 - 2 0 5 (June 1970) This theory considers the composite solid to be made up of discreet volume elements with characteristics related to material structure and imperfections. The elemental strengths are a statistical quantity and accumulation of fractures of these elements leads to failure. The theory is applied to composite materials reinforced with whiskers and continuous fibres and comparison with experimental data shows good agreement. (70/1/69)
Mechanical and microscopical investigation of SiC whiskers OP HET VELD, A. J. G. and VELDKAMP, J. D. E. Fibre Science and Technology, Vol 2, No 4, p 269 (April 1970) Measurements of r o o m temperature tensile strength and Young's modulus of hair-like whiskers of SiC grown by a vapour liquid-solid method and of ribbon like whiskers grown by the Lely process are reported. Amongst the conclusions are that a tapered whisker is unlikely to have one Young's modulus, holes in the core o f the hair-like whiskers markedly lower stiffness and strength and that the stress concentrating factor of defects can probably be reduced by a surface layer of SiO2 obtained during preparation. (70/1/61)
Fracture of bone PIEKARSKI, K. J o f Applied Physics, Vo141, No 1, pp 215 - 223 (January 1970) The energy required to propogate a fracture through bone was studied using an Instron machine. Metallographic and scanning electron microscope techniques were used to observe the fracture mechanism. At low strain rates bone appears to be a tough material, but fracture in a more brittle mode occurs at high strain rates. Pullout o f b o t h the large scale fibre structure (esteons) and very much smaller fibrils (probably mineral crystallites) was observed in slow fractures. The presence of discontinuities such as blood vessels tends to enhance rather than reduce the toughness of bone. (70/1/62)
cost means that the lead of the British Coal Utilization Research Association is producing carbon fibre at an expected price of £1/lb should be followed up without delay. After the solvent treatment of coal and distillation, the remaining product, coal extract, is used for the manufacture of carbon fibre, polymer and specialist and electrode coke and it is concluded that cheap carbon fibre such as this could benefit many research applications of carbon fibres which at the moment are stifled by its high cost. (70/1]63)
Whisker sorter is key to high strength composites. PETERS, D.
The Engineer, p 22 (April 1970) The Explosives Research and Development Establishment and Glass Developments Ltd have produced a classification technique suitable for all types of whisker. A suspension of the fibres is fed onto a rotating cylindrical screen and as it drains through the long fibres are retained and subsequently removed by water or air jets. A complete set of rotary screens is available from 160 wires/cm to 1-25. A complete fibre classification unit as installed by Lonza Ltd of Switzerland is shown schematically. (70/1/64)
The tensile behaviour of fibrous materials at high rates of strain and subambient temperatures SKELTON, J. Mat Res and Standards, Vol 10, No 6, pp 20 - 25 (June 1970) Man-made textile fibres, glass fibres and metal fibres, all potential reinforcing materials, have been tested in the strain-rate range 1 - 14 000%/s and the subambient temperature range 70°F to - 3 2 0 ° F . Data on elongation r u p t u r e - stress, tenacity and initial modulus are presented for the 5 fibretypes. A detailed description of the test methods used is also given. (70/1/65)
Carbon fibre from coal - w h i c h is not for burning PETERS, D. The Engineer, Vol231, No 5971, p 30 (July 1970)
Interfacial tractions in a fibrereinforced elastic composite material SMITH, G. E. and SPENCER, A. J. M. J o f Mech and Physics o f Solids, Vol 18, No 2 (April 1970)
The application of carbon fibres to the more exotic fields in view of their high
A mathematical analysis of the problem of the forces acting over the
324
COMPOSITESSeptember 1970
fibre-matrix interface and the conditions governing fracture of that interface. The composite is regarded as consisting of circular cylindrical elements and solutions are obtained for stress and displacement of a typical element under boundary conditions which approximate to those of an element in the interior of the composite. It is shown that large shear stresses can occur near the ends of the element, which may tend to break the interracial bond. (70/1/66)
Mesure statique de Module D'Young de fibres VERCHERY, G. Fibre Science and Technology, Vol 2, No 4, p 283 (April 1970) The theory and practical method of measuring the static Young's Modulus of fibres of tungsten, boron and silicon carbide are given and the results of both are compared. The principal source o f error is said to be the measurement of fibre diameter which occurs as the term d-4 in the expression for the static Young's Modulus. The moduli of refractory fibres are found to be in agreement with those measured dynamically and those reported in the literature. (7011/67).
Variational bounds of transport properties of composite materials YEH, R. H. T. J of Applied Physics, Vol 41, No 1, pp 224 - 226 (January 1970) The electrical properties of composite materials are treated theoretically. Relative merits, physical interpretations, limitations and generalisations o f various bounds applied to composites are discussed. (70/1/68)
A statistical theory of material strength with application to composite materials ZWEBEN, C. and ROSEN, B. W. J o f the Mech Physics of Solids, Vol 18, No 3, pp 189 - 2 0 5 (June 1970) This theory considers the composite solid to be made up of discreet volume elements with characteristics related to material structure and imperfections. The elemental strengths are a statistical quantity and accumulation of fractures of these elements leads to failure. The theory is applied to composite materials reinforced with whiskers and continuous fibres and comparison with experimental data shows good agreement. (70/1/69)