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Calculation of edge stresses in multilayer laminates by sub-structuring
Abstracts of journals Prepared by P. Curtis, K. Phillips, P. Manders and 7". Feest
CARBON MA TRICES
Fiber-matrix interactions in unidirectional carbon-carbon composites Bradshaw, W.G. and Vidoz, A.E., American Ceramic Society Bulletin Vol 57 No 2 (1978) p 193 Carbon fibre/carbon composites fabricated from a wide range of commercial fibres and pyrolised resin matrices are evaluated in simple tension. Both fibre and matrix are brittle, and to realise the fibres' ultimate strength the matrix must possess a failure strain above that of the fibres', a requirement strongly influenced by shrinkage stresses induced by pyrolysis and the resin formulation,
CEMENT MA TRICES An appraisal of steel reinforcement
tendons and prestressing tendons Evans, W., Concrete Vol 12 No 4 (1978) p 28 The main types of steel reinforcement for concrete are listed and the advantages and disadvantages of each are discussed, The yield stress, ductility, weldability and notch sensitivity of the steels are shown to be the important factors to consider when choosing a particular reinforcement as well as the steel composition.
Cracking and toughening of concrete and polymer-concrete dispersed with short steel wires Beaumont, P.W.R. and Aleszka. J.C., Journal of Materials Science Vol 13 (1978) pp 1749-1760 Reinforcement theories for brittle solids incorporating strong fibres are discussed with a view to making toughness and cracking stress predictions. Relevant parameters are critically examined and evaluated either by experiment, or calculation based on simple
44
assumptions. The theory is tested on short steel wire-reinforced concrete and polymethylmethacrylate impregnated concrete,
Inelastic behaviour in steel wire pull-out from Portland cement mOT-
tar Pinchin D.J. and Tabor, D., Journal of Materials Science Vo113 (1978) p 1261 An experimental study of the effect of the wire surface finish and externally applied pressure on the pull-out of stainless steel wire from Portland cement mortar is presented. The results show that an external pressure increases the pullout force due to the increased stress transfer at the interface. A small movement of the wire is shown to reduce the pull-out force, a result of cement densification near the wire surface leading to a reduction in the fibre/matrix misfit. A theoretical analysis of the pull-out force is presented and the importance of the Poisson contraction of the wire during pull-out is highlighted,
Properties of cement composites reinforced with Kevlar fibres Walton, P.L. and Majumdar, A.J., Journal of Materials Science Vol 13 (1978) p 1075 The mechanical properties of cement reinforced with 1.9% by volume of Kevlar fibre have been assessed as a function of time (up to 2 years) and exposure to air, water and natural weather environments. Uts was found to be unchanged, but strain to failure and impact strength increased with air storage but decreased with water storage. These changes are discussed in terms of the modification of matrix and interfacial properties. Fatigue is not considered to be a critical factor in the use of the material, even at stresses above the elastic limit. Fire tests were also performed on the material,
GENERA L An analytical study of the post buckling of laminated, anisotropic plates Chan, D.P., Fibre Science and Technology Vol 11 No 3 (May 1978) pp 165-187 Investigations were carried out on the elastic post buckling behaviour of iaminated anistropic plates; Love-Kirchhoff assumptions and the von-Karman large strain/displacement relations for thin plates were used. Calculated results were also verified against experimental data and other analytical results. Calculation of edge stresses in multilayer laminates by sub-structuring Wang, A.S.D. and Crossman, F.W., Journal of Composite Materials Vol 12, (January 1978) p 76 The significant stress concentrations which are generated at the free edges of laminates can generally only be calculated with numerical methods, eg the finite element procedure. For multilayer laminates the number of nodes in the grid becomes large and the computational requirement excessive, but this can be overcome by the sub-structuring approach of this paper. Specific examples are worked through for full, and sub-structured finite element computations. The chain-of-bundles probability model for the strength of fibrous materials I: analysis and conjectures Harlow, D.G. and Phoenix, S.L., Journal of Composite Materials Vol 12 (April 1978) pp 195-214 Analytical results are discussed for the chain-of-bundles probability model for the strength of fibrous materials using two load sharing rules for failed and non-failed fibres in a bundle; these are the equal load sharing rule of classical analysis and a local load sharing rule which is more realistic for composite materials. Numerical solutions of this model are considered.
COMPOSITES. JANUARY 1979
CARBON MA TRICES
Fiber-matrix interactions in unidirectional carbon-carbon composites Bradshaw, W.G. and Vidoz, A.E., American Ceramic Society Bulletin Vol 57 No 2 (1978) p 193 Carbon fibre/carbon composites fabricated from a wide range of commercial fibres and pyrolised resin matrices are evaluated in simple tension. Both fibre and matrix are brittle, and to realise the fibres' ultimate strength the matrix must possess a failure strain above that of the fibres', a requirement strongly influenced by shrinkage stresses induced by pyrolysis and the resin formulation,
CEMENT MA TRICES An appraisal of steel reinforcement
tendons and prestressing tendons Evans, W., Concrete Vol 12 No 4 (1978) p 28 The main types of steel reinforcement for concrete are listed and the advantages and disadvantages of each are discussed, The yield stress, ductility, weldability and notch sensitivity of the steels are shown to be the important factors to consider when choosing a particular reinforcement as well as the steel composition.
Cracking and toughening of concrete and polymer-concrete dispersed with short steel wires Beaumont, P.W.R. and Aleszka. J.C., Journal of Materials Science Vol 13 (1978) pp 1749-1760 Reinforcement theories for brittle solids incorporating strong fibres are discussed with a view to making toughness and cracking stress predictions. Relevant parameters are critically examined and evaluated either by experiment, or calculation based on simple
44
assumptions. The theory is tested on short steel wire-reinforced concrete and polymethylmethacrylate impregnated concrete,
Inelastic behaviour in steel wire pull-out from Portland cement mOT-
tar Pinchin D.J. and Tabor, D., Journal of Materials Science Vo113 (1978) p 1261 An experimental study of the effect of the wire surface finish and externally applied pressure on the pull-out of stainless steel wire from Portland cement mortar is presented. The results show that an external pressure increases the pullout force due to the increased stress transfer at the interface. A small movement of the wire is shown to reduce the pull-out force, a result of cement densification near the wire surface leading to a reduction in the fibre/matrix misfit. A theoretical analysis of the pull-out force is presented and the importance of the Poisson contraction of the wire during pull-out is highlighted,
Properties of cement composites reinforced with Kevlar fibres Walton, P.L. and Majumdar, A.J., Journal of Materials Science Vol 13 (1978) p 1075 The mechanical properties of cement reinforced with 1.9% by volume of Kevlar fibre have been assessed as a function of time (up to 2 years) and exposure to air, water and natural weather environments. Uts was found to be unchanged, but strain to failure and impact strength increased with air storage but decreased with water storage. These changes are discussed in terms of the modification of matrix and interfacial properties. Fatigue is not considered to be a critical factor in the use of the material, even at stresses above the elastic limit. Fire tests were also performed on the material,
GENERA L An analytical study of the post buckling of laminated, anisotropic plates Chan, D.P., Fibre Science and Technology Vol 11 No 3 (May 1978) pp 165-187 Investigations were carried out on the elastic post buckling behaviour of iaminated anistropic plates; Love-Kirchhoff assumptions and the von-Karman large strain/displacement relations for thin plates were used. Calculated results were also verified against experimental data and other analytical results. Calculation of edge stresses in multilayer laminates by sub-structuring Wang, A.S.D. and Crossman, F.W., Journal of Composite Materials Vol 12, (January 1978) p 76 The significant stress concentrations which are generated at the free edges of laminates can generally only be calculated with numerical methods, eg the finite element procedure. For multilayer laminates the number of nodes in the grid becomes large and the computational requirement excessive, but this can be overcome by the sub-structuring approach of this paper. Specific examples are worked through for full, and sub-structured finite element computations. The chain-of-bundles probability model for the strength of fibrous materials I: analysis and conjectures Harlow, D.G. and Phoenix, S.L., Journal of Composite Materials Vol 12 (April 1978) pp 195-214 Analytical results are discussed for the chain-of-bundles probability model for the strength of fibrous materials using two load sharing rules for failed and non-failed fibres in a bundle; these are the equal load sharing rule of classical analysis and a local load sharing rule which is more realistic for composite materials. Numerical solutions of this model are considered.
COMPOSITES. JANUARY 1979