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Stress field evaluation in photoelastic anisotropic materials: experimental numerical technique
(January 1981) pp 71-78 The purpose of this paper is to show that the equations of three-dimensional anistropic elasticity can be split into two independent systems and that this procudure, which is possible for isotropic materials, may be carried over to the anisotropic plate. A method for determining the mode 1 delamination fracture toughness of elastic and viscoelastic composite materials Devitt, D.F., Schapery, R.A. and Bradley W.L. Journal o f Composite Materials Vol 14 (October 1980)pp 270-285 A simple approach to the determination of delamination fracture toughness in the opening mode has been developed using a split beam and a nonlinear analysis. The analysis has been confirmed with experimental measurements on glass/epoxy systems using specimens of three thicknesses, tested over a wide range of crack growth rates. The measured range of energy release rates of 525-1000 Nm -~ for the range of crack growth rates studied is shown to be consistent with predictions from an idealized viscoelastic crack g r o w t h t h e o r y and v i s c o e l a s t i c behaviour of the resin as determined from creep/recovery tests. Non linear viscoelastic behaviour of polypropylene and glass reinforced polypropylene in creep Gupta, Vidya Bhushan, and Lahiri, Jhumur Journal o f Composite Materials Vol 14 (October 1980) pp 286-296 Isothermal creep tests have been carded out on unreinforced and glass fibre reinforced polypropylene samples under uniaxial tension. Experiments were performed at different stress levels and at various temperatures up to 60°C. The initial time-independent deformation of the polypropylene appears to show characteristics typical of an elastic solid. The subsequent time-dependent deformation increases with time and stress typifying viscoelastic behaviour. Incorporation of glass fibres into the polypropylene renders the structure less deformable; the compliance is reduced and the viscoelastic effects are suppressed. On the probability of failure In the chain-of-bundles model Bergman, Bo Journal of Composite Materials Vol 15 (January 1981) p92 A chain-of bundles model is used to give refined bounds on the asymptotic. strength distribution of a unidirectional fibre composite, applicable to a general failure model.
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Property changes of a graphite/epoxy composite exposed to nonionizing space parameters Phelps, Henry R. and Long, Edward R. Journal o f Composite Materials Vol 14 (October 1980)pp 334-341 A study has been made of the changes in mass, thickness and flexural properties of initially wet and dry specimens of graphite/epoxy composite specimens due to the equivalent of eight weeks of e x p o s u r e to n o n i o n i z i n g space e n v i r o n m e n t a l parameters. These parameters were near and middle solar u v irradience, high vacuum and temperature. Changes were observed in the mass, dimensions and surface morphology of the specimens, though the flexural properties were not affected. Combined u v and elevated temperature environments had synergistic effects on the properties of the specimens. Stress field evaluation in photoelastic anisotropic materials: experimental numerical technique Voloshin, Arkady Journal of Composite Materials Vol 14 (October 1980) pp 342-350 An experimental numerical technique has been developed for stress field evaluation in photoelastic anisotropic materials. The method is based on using experimental data and basic elasticity theory to obtain an overdetermined solution, and is compared favourably with results obtained by two other techniques (finite element and modified shear difference). Application of the analysis for experimental evaluation of stress-intensity factors, as well as stress field determination near a crack tip is proposed. Studies of impacted glass fibrereinforced composite laminates Takeda, N., Sierakowski, R.L. and Malvern, L.E. SA M P E Quarterly Vo112 No 2 (January 1981)pp 9-17 An experimental investigation of the sequential delamination of centrally impacted composite laminates is reported. The materials used were glass fibre/epoxy manufactured with prepreg tapes. Parameters such as impactor nose shape, impactor mass and kinetic energy, and ply orientation were varied to assess their effects on the fracture behaviour of the laminates. Studies of structure in carbonized composites from a phenolic resin and oxidized PAN fibres using chromic acid as an etchant Markovic, Vesna, and March, Harry
Carbon Vol 19 pp 209-211 Phenolic resin/PAN fibre composites were prepared with heat treatments at a number of temperatures between 423 and 1173 K. Optical and scanning electron microscopy of polished surfaces indicated a fusing of the two materials into a homogeneous matrix. However, SEM of samples etched with chromic acid showed that the identity of the materials was preserved. Transverse sections of PAN fibres heat treated at greater then 973 K exhibited a selective etching suggestive of a strain/core fibre composition. Thermomechanical properties of particle composites in their transition region Paipetis, S.A. Fibre Science and Technology Vol 13 No 6 (November 1980) pp 449-463 An investigation was carried out on the t h e r m o m e c h a n i c a l b e h a v i o u r of polymeric materials containing filler particles in the region of the glass transition temperature of the materials. It was shown analytically that introducing such reinforcing particles would increase Tg to an extent proportional to the reinforcing effect. Previously reported experimental work confirms this analytical proposition, except for composites in which mat fix/particle bonding is poor. This later was confirmed by e x p e r i m e n t s . Particle geometry and topology were found to affect Tg considerably. Thickness and laminating effects on fracture behaviour of glass fibre composites Garg, A.C. Fibre Science and Technology Vol 14 No 1 (January 1981) pp 27-39 The effect of laminate thickness and method of lamination on the fracture of random glass fibre-reinforced resin was studied using R-curves. It was found that thickness did not significantly affect the fracture characteristics, but that delayed lamination (that is, prepared over a period of 4 days) does to some extent. Using the R-curves, analytical relationships have been developed and these were used to predict the residual strength characteristics and the fracture toughness. Toughness testing of composite materials Miller, A.G., Hertzberg, P.E. and Rantala, V.W. SAMPE Quarterly Vol 12 No 2 (January 1981)pp 36-42 The development of fracture toughness and instrumented impact testing proce-
COMPOSITES. OCTOBER 1981
296
Property changes of a graphite/epoxy composite exposed to nonionizing space parameters Phelps, Henry R. and Long, Edward R. Journal o f Composite Materials Vol 14 (October 1980)pp 334-341 A study has been made of the changes in mass, thickness and flexural properties of initially wet and dry specimens of graphite/epoxy composite specimens due to the equivalent of eight weeks of e x p o s u r e to n o n i o n i z i n g space e n v i r o n m e n t a l parameters. These parameters were near and middle solar u v irradience, high vacuum and temperature. Changes were observed in the mass, dimensions and surface morphology of the specimens, though the flexural properties were not affected. Combined u v and elevated temperature environments had synergistic effects on the properties of the specimens. Stress field evaluation in photoelastic anisotropic materials: experimental numerical technique Voloshin, Arkady Journal of Composite Materials Vol 14 (October 1980) pp 342-350 An experimental numerical technique has been developed for stress field evaluation in photoelastic anisotropic materials. The method is based on using experimental data and basic elasticity theory to obtain an overdetermined solution, and is compared favourably with results obtained by two other techniques (finite element and modified shear difference). Application of the analysis for experimental evaluation of stress-intensity factors, as well as stress field determination near a crack tip is proposed. Studies of impacted glass fibrereinforced composite laminates Takeda, N., Sierakowski, R.L. and Malvern, L.E. SA M P E Quarterly Vo112 No 2 (January 1981)pp 9-17 An experimental investigation of the sequential delamination of centrally impacted composite laminates is reported. The materials used were glass fibre/epoxy manufactured with prepreg tapes. Parameters such as impactor nose shape, impactor mass and kinetic energy, and ply orientation were varied to assess their effects on the fracture behaviour of the laminates. Studies of structure in carbonized composites from a phenolic resin and oxidized PAN fibres using chromic acid as an etchant Markovic, Vesna, and March, Harry
Carbon Vol 19 pp 209-211 Phenolic resin/PAN fibre composites were prepared with heat treatments at a number of temperatures between 423 and 1173 K. Optical and scanning electron microscopy of polished surfaces indicated a fusing of the two materials into a homogeneous matrix. However, SEM of samples etched with chromic acid showed that the identity of the materials was preserved. Transverse sections of PAN fibres heat treated at greater then 973 K exhibited a selective etching suggestive of a strain/core fibre composition. Thermomechanical properties of particle composites in their transition region Paipetis, S.A. Fibre Science and Technology Vol 13 No 6 (November 1980) pp 449-463 An investigation was carried out on the t h e r m o m e c h a n i c a l b e h a v i o u r of polymeric materials containing filler particles in the region of the glass transition temperature of the materials. It was shown analytically that introducing such reinforcing particles would increase Tg to an extent proportional to the reinforcing effect. Previously reported experimental work confirms this analytical proposition, except for composites in which mat fix/particle bonding is poor. This later was confirmed by e x p e r i m e n t s . Particle geometry and topology were found to affect Tg considerably. Thickness and laminating effects on fracture behaviour of glass fibre composites Garg, A.C. Fibre Science and Technology Vol 14 No 1 (January 1981) pp 27-39 The effect of laminate thickness and method of lamination on the fracture of random glass fibre-reinforced resin was studied using R-curves. It was found that thickness did not significantly affect the fracture characteristics, but that delayed lamination (that is, prepared over a period of 4 days) does to some extent. Using the R-curves, analytical relationships have been developed and these were used to predict the residual strength characteristics and the fracture toughness. Toughness testing of composite materials Miller, A.G., Hertzberg, P.E. and Rantala, V.W. SAMPE Quarterly Vol 12 No 2 (January 1981)pp 36-42 The development of fracture toughness and instrumented impact testing proce-
COMPOSITES. OCTOBER 1981