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The effects of flaws and voids on the shear properties of cfrp
fibres in the same matrix support the proposition.
The deformation and fracture behaviour of glass filled ABS Dover, I.R., Smith, I.O. and Chadwick, G.A. Journal of Materials Science Vo112 (June 1977) pp 1176-1184 30 wt % glass reinforcement of pigmented ABS containing 30 wt % rubber significantly increased fracture strength but decreased ductility, compared with the base polymer. Tests were carried out over a range of strain-rates and temperatures and the observed variation in fracture strength and morphology is explained in terms of the properties of an interfacial region adjacent to the fibres which possesses viscoelastic properties different from those of the bulk polymer.
The effects of flaws and voids on the shear properties of cfrp Hancox, N.L. Journal of Materials Science Vo112 (May 1977) pp 884-892 The shear properties of solid cfrp rods and tubes containing flaws and voids have been studied. The behaviour of tubes containing flaws parallel to the long axis can be described in terms of fracture mechanics. Solid rods are not particularly sensitive to flaws. Voids reduce shear properties steadily down to 30% of the void-free value at 5% voids. It is suggested that fracture mechanics cannot be used to analyse the shear properties of materials containing voids.
The effect of resin failure strain on the tensile properties of glass fibrereinforced polyester cross-ply laminates Garrett, K.W. and Bailey, J.E. Journal of Materials Science 1Ioi 12 (November 1977) pp 2189-2194 An investigation of the effect of resin properties on transverse cracking behaviour of glass fibre-reinforced polyester resin three-ply laminates has shown that the mechanical properties of the resins affect the stress level at which transverse cracking is initiated as well as the nature of the cracking behaviour. A flexibilizing resin was added to the polyester to produce five matrix systems with failure strains ranging from 1.75 to 11.1%. If fibre bonding is taken into account the Kies strain magnification theory can predict the general trend of the results.
COMPOSITES . JULY
1978
Elastic properties of randomly oriented short fibre-glass composites Mavera, M. Journal of Composite Materials Vo111 (April 1977) pp 235-24 7 Simplified equations are presented for the elastic properties of randomly oriented short glass fibre composites. The suggested equations for Young's modulus, the shear modulus and the Poisson's ratio are given in terms of the glass content and the Young's moduli of the constituents. The equations are applicable for fibre-glass volume fractions in the range of 0.1 to 0.4. Enhanced fracture strain of polypropylene by incorporation of thermo plastic fibres Campbell, D. and Qayyum. M.M. Journal of Materials Science Vo112 (December 1977) pp 2427-2434 The incorporation of continuous, uniaxially oriented, nylon and polyethylene terephthalate fibres into isotactic polypropylene leads to the expected increase in tensile strength as predicted by the rule of mixtures. The elongation to break, however, is found to be significantly in excess of those of the fibres and the matrix and increases with fibre volume fraction. This increase in ductility is attributed to the decrease in the spherulite size of the polypropylene and to restrained necking of the fibres due to transcrystalline growth at the fibre surface. Environmental effects on the elastic moduli of composite materials Shen, C-H and Springer G.S. Journal of Composite Materials Vol 11 (July 1977) pp 250-264 The buckling moduli of graphite/epoxy composites were measured over the temperature range 105 K to 422 K and at moisture contents ranging from 0% to 1.5%. The measurements were made using 0 °, 90 ° and n/4 laminates. A survey of existing data showing the effects of temperature and moisture content on the tensile and compressive moduli is also presented. Fatigue damage: stiffness/strength comparisons for composite materials O'Brien, T.K. and Reifsnider, K.L. Journal of Testing and Evaluation Vol 5 No 5 (September 1977) pp 384-393 A variety of boron/epoxy laminates were tested statically and in straincontrolled fatigue loading at 30 Hz, with a strain-amplitude ratio of one tenth for five different testing
sequences. A reduced stiffness analysis was used in conjunction with laminated plate theory to predict stiffness changes based on observed debonding and fibre breakage.
Fatigue fracture initiation in notched graphite-epoxy specimens Papirno, R. Journal of Composite Materials 1Iol 11 (January 1977) pp 41-50 A photomicrographic technique, previously developed for detecting fatigue cracking in metals, has been adapted for use with composite materials and results obtained with doubly notched graphite/epoxy specimens. Improving the fracture energy of carbon fibre-reinforced plastics by delamination promoters Favre, J-P. Journal of Materials Science Vol 12 (January 1977} pp 43-50 The effect of delamination promoters on the Charpy impact energy and other mechanical properties of carbon fibre-reinforced plastics has been studied. The delamination promoters consist of thin sheets of metallic or organic compounds which make the multiple splitting of samples at the time of impact much easier. Influence of environmental cycling on the mechanical properties of composite materials Lundemo. C.Y. and Thor S-E. Journal of Composite Materials Vo111 (July 1977) pp 276-284 Static and fatigue tests were carried out on cfrp specimens exposed to environmental conditions with the purpose of simulating the real environmental conditions for operational aircraft. The results show clear deterioration in both static and fatigue properties due to environmental exposure. The material becomes more ductile under the influence of moisture and after prolonged exposure debonding sets in. This degradation is accelerated if the specimens are preloaded. Low-cost composite primary structure Lloyd, M.S., O'Brien, W.L. and Parker, D.E. SAMPE Quarterly Vol 9
No 1 (October 1977)pp 28-39 The paper reviews the efforts in the US aerospace industry towards the development of a low-cost light weight advanced composite (boron/epoxy and graphite/epoxy) vertical stabilizer for possible application in the B-1 aircraft.
207
The deformation and fracture behaviour of glass filled ABS Dover, I.R., Smith, I.O. and Chadwick, G.A. Journal of Materials Science Vo112 (June 1977) pp 1176-1184 30 wt % glass reinforcement of pigmented ABS containing 30 wt % rubber significantly increased fracture strength but decreased ductility, compared with the base polymer. Tests were carried out over a range of strain-rates and temperatures and the observed variation in fracture strength and morphology is explained in terms of the properties of an interfacial region adjacent to the fibres which possesses viscoelastic properties different from those of the bulk polymer.
The effects of flaws and voids on the shear properties of cfrp Hancox, N.L. Journal of Materials Science Vo112 (May 1977) pp 884-892 The shear properties of solid cfrp rods and tubes containing flaws and voids have been studied. The behaviour of tubes containing flaws parallel to the long axis can be described in terms of fracture mechanics. Solid rods are not particularly sensitive to flaws. Voids reduce shear properties steadily down to 30% of the void-free value at 5% voids. It is suggested that fracture mechanics cannot be used to analyse the shear properties of materials containing voids.
The effect of resin failure strain on the tensile properties of glass fibrereinforced polyester cross-ply laminates Garrett, K.W. and Bailey, J.E. Journal of Materials Science 1Ioi 12 (November 1977) pp 2189-2194 An investigation of the effect of resin properties on transverse cracking behaviour of glass fibre-reinforced polyester resin three-ply laminates has shown that the mechanical properties of the resins affect the stress level at which transverse cracking is initiated as well as the nature of the cracking behaviour. A flexibilizing resin was added to the polyester to produce five matrix systems with failure strains ranging from 1.75 to 11.1%. If fibre bonding is taken into account the Kies strain magnification theory can predict the general trend of the results.
COMPOSITES . JULY
1978
Elastic properties of randomly oriented short fibre-glass composites Mavera, M. Journal of Composite Materials Vo111 (April 1977) pp 235-24 7 Simplified equations are presented for the elastic properties of randomly oriented short glass fibre composites. The suggested equations for Young's modulus, the shear modulus and the Poisson's ratio are given in terms of the glass content and the Young's moduli of the constituents. The equations are applicable for fibre-glass volume fractions in the range of 0.1 to 0.4. Enhanced fracture strain of polypropylene by incorporation of thermo plastic fibres Campbell, D. and Qayyum. M.M. Journal of Materials Science Vo112 (December 1977) pp 2427-2434 The incorporation of continuous, uniaxially oriented, nylon and polyethylene terephthalate fibres into isotactic polypropylene leads to the expected increase in tensile strength as predicted by the rule of mixtures. The elongation to break, however, is found to be significantly in excess of those of the fibres and the matrix and increases with fibre volume fraction. This increase in ductility is attributed to the decrease in the spherulite size of the polypropylene and to restrained necking of the fibres due to transcrystalline growth at the fibre surface. Environmental effects on the elastic moduli of composite materials Shen, C-H and Springer G.S. Journal of Composite Materials Vol 11 (July 1977) pp 250-264 The buckling moduli of graphite/epoxy composites were measured over the temperature range 105 K to 422 K and at moisture contents ranging from 0% to 1.5%. The measurements were made using 0 °, 90 ° and n/4 laminates. A survey of existing data showing the effects of temperature and moisture content on the tensile and compressive moduli is also presented. Fatigue damage: stiffness/strength comparisons for composite materials O'Brien, T.K. and Reifsnider, K.L. Journal of Testing and Evaluation Vol 5 No 5 (September 1977) pp 384-393 A variety of boron/epoxy laminates were tested statically and in straincontrolled fatigue loading at 30 Hz, with a strain-amplitude ratio of one tenth for five different testing
sequences. A reduced stiffness analysis was used in conjunction with laminated plate theory to predict stiffness changes based on observed debonding and fibre breakage.
Fatigue fracture initiation in notched graphite-epoxy specimens Papirno, R. Journal of Composite Materials 1Iol 11 (January 1977) pp 41-50 A photomicrographic technique, previously developed for detecting fatigue cracking in metals, has been adapted for use with composite materials and results obtained with doubly notched graphite/epoxy specimens. Improving the fracture energy of carbon fibre-reinforced plastics by delamination promoters Favre, J-P. Journal of Materials Science Vol 12 (January 1977} pp 43-50 The effect of delamination promoters on the Charpy impact energy and other mechanical properties of carbon fibre-reinforced plastics has been studied. The delamination promoters consist of thin sheets of metallic or organic compounds which make the multiple splitting of samples at the time of impact much easier. Influence of environmental cycling on the mechanical properties of composite materials Lundemo. C.Y. and Thor S-E. Journal of Composite Materials Vo111 (July 1977) pp 276-284 Static and fatigue tests were carried out on cfrp specimens exposed to environmental conditions with the purpose of simulating the real environmental conditions for operational aircraft. The results show clear deterioration in both static and fatigue properties due to environmental exposure. The material becomes more ductile under the influence of moisture and after prolonged exposure debonding sets in. This degradation is accelerated if the specimens are preloaded. Low-cost composite primary structure Lloyd, M.S., O'Brien, W.L. and Parker, D.E. SAMPE Quarterly Vol 9
No 1 (October 1977)pp 28-39 The paper reviews the efforts in the US aerospace industry towards the development of a low-cost light weight advanced composite (boron/epoxy and graphite/epoxy) vertical stabilizer for possible application in the B-1 aircraft.
207