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Interlaminar shear fatigue of pultruded graphite fibre-polyester composites
crack is used to propagate in plane strain a cohesive fracture within a block of resin, or an adhesive interface failure between resin and a substrate. High speed motion photography records the crack growth at velocities up to 1.5 m/s. An elastic analysis provides fracture energy values as a function of crack velocity, and shows a peak value is attained within the velocity range,
The fracture toughness of reinforced polyurethane foam Cotgreave, T. and Shortall, J.B. Journal of Materials Science Vol 13 (1978) pp 722-730 The fracture processes occuring in glass fibre-reinforced polyurethane foam have been investigated and fracture toughness measurements performed as a function of fibre length and concentration. The glass fibres were found to enhance the natural toughening mechanism of the foam, based on crack arrest and diversion. Fracture toughness increased with increasing fibre concentration and also with higher levels of fibre surface treatment, The reinforcement efficiency varied with fibre length, an optimum length near the critical fibre length proving most effective, Influence of surface and environmental thermal properties on moisture in composites Tompkins, S.S. Fibre Science and Technology Vol 11 No 3 (May 1978) pp 189-197 An analytical study of the influence of surface and environmental thermal properties on the moisture absorption of fibre-reinforced platics, subjected to convection and solar radiation, was made. Predicted moisture contents, based on conditions at the heated surface and in the ambient air, were compared for both short and long term exposures over a range of values for emittance, solar absorption, convective heat transfer coefficient, solar radiation and surface orientation relative to the sun. Calculations showed that absorption and heat transfer coefficients have significant effects on moisture content,
lnterlaminar shear fatigue of pultruded graphite fibre-polyester composites Oharan, C.K.H. Journal of Materials Science Vol 13 (1978) p 1243
50
The effect of cyclic loading on the interlaminar shear strength (ilss) of pultruded graphite at two fibre volume fractions (0.33 and 0.5) has been studied. The material degradation under these cycling conditions is greater than in flexural fatigue. The ilss values were significantly lower than similar graphite/epoxy composites. Little volume fraction effect on the fatigue ilss at high cycles was detected. A critical stress of 15 MN/m 2 is determined above which interlaminar shear fatigue failure did not occur within 107 cycles.
iron/boron/molybdenum alloy were determined at room temperature, as a function of ply orientation. It was found that the moduli of the laminates showed less dependence on included angle than those of equivalent fibre-reinforced composites. It is suggested, however, that ribbons with aspect ratios in excess of about 200 (compared with the ratio of 25 for ribbons reported) will be needed to obtain laminates having transverse strengths in excess of 50% of their longitudinal strengths.
NDT of DC-10 graphite-epoxy rudder Langmuir-type model for anomalous moisture diffusion in composite resins Carter, H.G. and Kibler, K.G. Journal of Composite Materials Vol 12 (April 1978) pp 118-131 A generalised linear model is presented for the diffusion of water in an epoxy matrix composite. The model is applied to anomalous moisture uptake data for 5208 resin exposed to several relative humidities for two years and the authors conclude that the absorption anomaly does not result from non-linear (eg concentration-dependent) effects.
Low energy impact behaviour of composite panels Aleszka, J-C.JournalofTestingand Evaluation Vol 6 No 3 (1978) p 202 Eight ply graphite epoxy ( 45 °, 0 °, 90 °) panels are impacted by a falling weight designed to simulate blunt object impact typical of ground handling and maintenance of aircraft. The test set-up is instrumented for load and energy recording which are predictive of incipient damage. Between 1 m/s and 5 m/s, the load and energy for incipient and full penetration damage are independent of impactor velocity, The mechanical behaviour of polysuifone matrix composites reinforced with amorphous metal ribbons Goldwasser, D.J., Otocka, E.P. and Kear, B.H., Materials Science and Engineering Vol 34 No 2 (July 1978) pp 139-146 Tensile and flexural properties of laminates made from polysulphone reinforced with ribbons of amorphous
Hagemaier, D.J., Materials Evaluation Vo136 No 6 (May 1978) pp 57-61 The Douglas Aircraft Co has fabricated ten composite ruddersfor the DC-10 which will be put in service for five years. Ultrasonic testing techniques will be employed at intervals of 3000 flight hours to check for cracking or delamination. The details of these techniques are presented in this paper. A new method for the determination of fibre concentrations in organic fibre-reinforced composites (technical note) Naar, R.Z., Panora, R.A.Jr, Dexter Cook, C. and Halpin, B.M.Jr Fibre Science and Technology Vol 11 No 3 (May 1978) pp 237-241 The hydrogen to nitrogen ratios of Kevlar and cured epoxy resin (0.37 and 2.70, respectively, determined by measurement of the individual element concentrations using a combustion-gas chromatography elemental analyzer) are used to calculate the corresponding weight ratio in a composite constructed from these two materials in known proportion. Determination of the hydrogen to nitrogen weight ratio of a composite specimen by the same technique gives the fibre concentration in that specimen.
On the mechanism of tensile fracture in notched fibre reinforced plastics Potter, R.T. Proceedings of the Royal Society of London A 361 (1978) pp 325-341 By observation of the tensile fracture processes occurring in continuous fibre-reinforced plastics, the micro-structural factors which govern the unstable propagation of a
COMPOSITES . JANUARY
1979
The fracture toughness of reinforced polyurethane foam Cotgreave, T. and Shortall, J.B. Journal of Materials Science Vol 13 (1978) pp 722-730 The fracture processes occuring in glass fibre-reinforced polyurethane foam have been investigated and fracture toughness measurements performed as a function of fibre length and concentration. The glass fibres were found to enhance the natural toughening mechanism of the foam, based on crack arrest and diversion. Fracture toughness increased with increasing fibre concentration and also with higher levels of fibre surface treatment, The reinforcement efficiency varied with fibre length, an optimum length near the critical fibre length proving most effective, Influence of surface and environmental thermal properties on moisture in composites Tompkins, S.S. Fibre Science and Technology Vol 11 No 3 (May 1978) pp 189-197 An analytical study of the influence of surface and environmental thermal properties on the moisture absorption of fibre-reinforced platics, subjected to convection and solar radiation, was made. Predicted moisture contents, based on conditions at the heated surface and in the ambient air, were compared for both short and long term exposures over a range of values for emittance, solar absorption, convective heat transfer coefficient, solar radiation and surface orientation relative to the sun. Calculations showed that absorption and heat transfer coefficients have significant effects on moisture content,
lnterlaminar shear fatigue of pultruded graphite fibre-polyester composites Oharan, C.K.H. Journal of Materials Science Vol 13 (1978) p 1243
50
The effect of cyclic loading on the interlaminar shear strength (ilss) of pultruded graphite at two fibre volume fractions (0.33 and 0.5) has been studied. The material degradation under these cycling conditions is greater than in flexural fatigue. The ilss values were significantly lower than similar graphite/epoxy composites. Little volume fraction effect on the fatigue ilss at high cycles was detected. A critical stress of 15 MN/m 2 is determined above which interlaminar shear fatigue failure did not occur within 107 cycles.
iron/boron/molybdenum alloy were determined at room temperature, as a function of ply orientation. It was found that the moduli of the laminates showed less dependence on included angle than those of equivalent fibre-reinforced composites. It is suggested, however, that ribbons with aspect ratios in excess of about 200 (compared with the ratio of 25 for ribbons reported) will be needed to obtain laminates having transverse strengths in excess of 50% of their longitudinal strengths.
NDT of DC-10 graphite-epoxy rudder Langmuir-type model for anomalous moisture diffusion in composite resins Carter, H.G. and Kibler, K.G. Journal of Composite Materials Vol 12 (April 1978) pp 118-131 A generalised linear model is presented for the diffusion of water in an epoxy matrix composite. The model is applied to anomalous moisture uptake data for 5208 resin exposed to several relative humidities for two years and the authors conclude that the absorption anomaly does not result from non-linear (eg concentration-dependent) effects.
Low energy impact behaviour of composite panels Aleszka, J-C.JournalofTestingand Evaluation Vol 6 No 3 (1978) p 202 Eight ply graphite epoxy ( 45 °, 0 °, 90 °) panels are impacted by a falling weight designed to simulate blunt object impact typical of ground handling and maintenance of aircraft. The test set-up is instrumented for load and energy recording which are predictive of incipient damage. Between 1 m/s and 5 m/s, the load and energy for incipient and full penetration damage are independent of impactor velocity, The mechanical behaviour of polysuifone matrix composites reinforced with amorphous metal ribbons Goldwasser, D.J., Otocka, E.P. and Kear, B.H., Materials Science and Engineering Vol 34 No 2 (July 1978) pp 139-146 Tensile and flexural properties of laminates made from polysulphone reinforced with ribbons of amorphous
Hagemaier, D.J., Materials Evaluation Vo136 No 6 (May 1978) pp 57-61 The Douglas Aircraft Co has fabricated ten composite ruddersfor the DC-10 which will be put in service for five years. Ultrasonic testing techniques will be employed at intervals of 3000 flight hours to check for cracking or delamination. The details of these techniques are presented in this paper. A new method for the determination of fibre concentrations in organic fibre-reinforced composites (technical note) Naar, R.Z., Panora, R.A.Jr, Dexter Cook, C. and Halpin, B.M.Jr Fibre Science and Technology Vol 11 No 3 (May 1978) pp 237-241 The hydrogen to nitrogen ratios of Kevlar and cured epoxy resin (0.37 and 2.70, respectively, determined by measurement of the individual element concentrations using a combustion-gas chromatography elemental analyzer) are used to calculate the corresponding weight ratio in a composite constructed from these two materials in known proportion. Determination of the hydrogen to nitrogen weight ratio of a composite specimen by the same technique gives the fibre concentration in that specimen.
On the mechanism of tensile fracture in notched fibre reinforced plastics Potter, R.T. Proceedings of the Royal Society of London A 361 (1978) pp 325-341 By observation of the tensile fracture processes occurring in continuous fibre-reinforced plastics, the micro-structural factors which govern the unstable propagation of a
COMPOSITES . JANUARY
1979