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Some fundamental principles associated with composite materials
HECKER, S. S., HAMILTON, C. H. and EBERT, L. J. Improved fibre composite tensile performance by mechanical residual stress relief ASM Trans Quarterly, Vol 62, No 3, pp 740 - 748 (1969) A composite model consisting of a cylindrical copper core in a cylinder of steel was used to study the residual stresses resulting from differences in thermal expansion of the component metals. It was found that the tensile behaviour of the composite cylinder was improved by removing the residual stresses by means of a pre-strain treatment which gave a small permanent strain. It was confirmed that this method o f improvement could be used in a real composite of tungsten-reinforced copper, eg a 20% elevation of the stress-strain curve was obtained for a composite of 20% vol fibre. (70/1/21) HUNT, R. E. How to select fillers and reinforcements for thermoplastics Plastics Technology, Vol 15, No 12, pp 3 3 - 4 3 (1969) A review is given of materials commercially available as fillers for thermoplastics. These include glass, asbestos, talc, calcium carbonate and calcium metasilicate. Subjects discussed include the cost of the filler particles. Details of the use and production of the filled plastics are given. (70/1/22) MEWES, D. R. Fabrics of high tenacity polyester yarns and their use for coated and rubberised products Textil Praxis International, Vol 3, pp 62 - 65 {1969) Fabrics woven from high tenacity polyester yarn have high load resistance and low percentage elongation. They are therefore particularly suitable for coating and rubberising. The properties and production of light, high strength, wear resistant and comparitively cheap composites of polyester fabric and rubber or plastics are described. (70/1/23) MILEIKO, S. T. The tensile strength and ductility of continuous fibre composites Journal o f Materials Science, Vol 4, No 11, pp 974 - 9 7 7 (November 1969)
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COMPOSITES March 1970
Considering a composite where fibres and matrix are ductile, a plastic instability approach is presented to obtain expressions for the strength and elongation at fracture for that composite. Experimental results which are in very close agreement with the theory are presented. (70/1/24)
ROTHWELL, A. Optimum fibre orientations for the buckling of thin plates of composite materials Fibre Science and Technology, Vol 2, No 2, p 111 (October 1969) The o p t i m u m symetrical fibre orientations for a thin fibre-reinforced plate to resist buckling are calculated. It is shown, however, that in practice other arrangements which allow sufficient stiffness to resist buckling y e t which do not allow the maximum permitted fibre stress to be exceeded have to be considered. Maximum buckling coefficients with corresponding fibre orientations are determined for a symmetric three fibre system in compression and an assymmetrical two fibre system in shear and a parameter which relates maximum fibre stress to plate buckling stress is introduced. (70/1/25)
TSAI, S. W. Some fundamental principles associated with composite materials Plastics and Polymers, Vol 37, No 131, pp 391 - 395 (October 1969) The heterogeneity and anisotropy aspects of the stress analysis of composite materials are discussed. A number of concepts and approaches such as shear lag and netting analysis are denounced as invalid or at least outdated. Use of elasticity theory is advocated and its extension into the nonlinear range for composite materials is called for. Extensive application of advanced analysis is prevented by inability to solve physically or geometrically non-linear problems, and lack of empirical studies of composite materials under simple and combined stresses. (70/1/26)
WOLSON, E. A. and PARSONS, B. The finite element analysis of filament-reinforced axisymmetric bodies Fibre Science and Technology, Vol 2, No 2, p 155 {October 1969)
Finite element analysis is applied to the problem of axisymmetric composite cylinders firstly to assess the accuracy of anisotropic laws of elasticity applied to such systems and secondly to demonstrate its usefulness in the evaluation of stress distribution within them. The merits of approximate anisotropic stress/strain laws applied to these systems are assessed and the results of an analysis of a thick walled cylinder reinforced with shells of filaments at different radii are given. The analysis is thought to be of practical use in view of the increasing employment of tape winding processes for composite manufacture. (70/1/27)
WU, C. I. and VINSON, J. R. The natural vibrations of plates composed of composite materials Fibre Science and Technology, Vol 2, No 2, p 97 {October 1969} It is shown that the classical theory of orthotropic plates is inapplicable to composite materials in which the ratio of in plane modulus to transverse shear modulus is very high and a set of governing equations is derived mathematically for the study of free vibrations of rectangular plates composed o f an orthotropic material. It is concluded that the effects of transverse shear depravation as well as rotary inertia and transverse normal stress cannot be discounted with certain anistropic composite materials in a plate or shell structure. (70• 1/28)
V A R A T H A R A J U L U , V. K. and KAYEK, SABIH, I. Strain pulse propagation in composite elastic rods Fibre Science and Technology, Vol 2, No 1, p 9 (July 1969) Strain pulse propagation in composite rods, one having a large soft core surrounded by a thin stiff casing and the other having a small stiff core with a large soft casing is analyzed mathematically and the solution given as the sum of Fourier Integrals. It is concluded that composite rods subjected to the same total impact have dynamic strains at least 75% greater than those predicted by static analysis and that fact should be considered in the design of reinforced composites. (70/1/29)
]90
COMPOSITES March 1970
Considering a composite where fibres and matrix are ductile, a plastic instability approach is presented to obtain expressions for the strength and elongation at fracture for that composite. Experimental results which are in very close agreement with the theory are presented. (70/1/24)
ROTHWELL, A. Optimum fibre orientations for the buckling of thin plates of composite materials Fibre Science and Technology, Vol 2, No 2, p 111 (October 1969) The o p t i m u m symetrical fibre orientations for a thin fibre-reinforced plate to resist buckling are calculated. It is shown, however, that in practice other arrangements which allow sufficient stiffness to resist buckling y e t which do not allow the maximum permitted fibre stress to be exceeded have to be considered. Maximum buckling coefficients with corresponding fibre orientations are determined for a symmetric three fibre system in compression and an assymmetrical two fibre system in shear and a parameter which relates maximum fibre stress to plate buckling stress is introduced. (70/1/25)
TSAI, S. W. Some fundamental principles associated with composite materials Plastics and Polymers, Vol 37, No 131, pp 391 - 395 (October 1969) The heterogeneity and anisotropy aspects of the stress analysis of composite materials are discussed. A number of concepts and approaches such as shear lag and netting analysis are denounced as invalid or at least outdated. Use of elasticity theory is advocated and its extension into the nonlinear range for composite materials is called for. Extensive application of advanced analysis is prevented by inability to solve physically or geometrically non-linear problems, and lack of empirical studies of composite materials under simple and combined stresses. (70/1/26)
WOLSON, E. A. and PARSONS, B. The finite element analysis of filament-reinforced axisymmetric bodies Fibre Science and Technology, Vol 2, No 2, p 155 {October 1969)
Finite element analysis is applied to the problem of axisymmetric composite cylinders firstly to assess the accuracy of anisotropic laws of elasticity applied to such systems and secondly to demonstrate its usefulness in the evaluation of stress distribution within them. The merits of approximate anisotropic stress/strain laws applied to these systems are assessed and the results of an analysis of a thick walled cylinder reinforced with shells of filaments at different radii are given. The analysis is thought to be of practical use in view of the increasing employment of tape winding processes for composite manufacture. (70/1/27)
WU, C. I. and VINSON, J. R. The natural vibrations of plates composed of composite materials Fibre Science and Technology, Vol 2, No 2, p 97 {October 1969} It is shown that the classical theory of orthotropic plates is inapplicable to composite materials in which the ratio of in plane modulus to transverse shear modulus is very high and a set of governing equations is derived mathematically for the study of free vibrations of rectangular plates composed o f an orthotropic material. It is concluded that the effects of transverse shear depravation as well as rotary inertia and transverse normal stress cannot be discounted with certain anistropic composite materials in a plate or shell structure. (70• 1/28)
V A R A T H A R A J U L U , V. K. and KAYEK, SABIH, I. Strain pulse propagation in composite elastic rods Fibre Science and Technology, Vol 2, No 1, p 9 (July 1969) Strain pulse propagation in composite rods, one having a large soft core surrounded by a thin stiff casing and the other having a small stiff core with a large soft casing is analyzed mathematically and the solution given as the sum of Fourier Integrals. It is concluded that composite rods subjected to the same total impact have dynamic strains at least 75% greater than those predicted by static analysis and that fact should be considered in the design of reinforced composites. (70/1/29)