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On the stress distribution in a laminal
In this paper, the state-of-the-art of delamination behaviour is reviewed. Some of the aspects considered are the causes of delamination and their effect on structural performance, analytical and experimental techniques to predict behaviour and preventative methods to delay the onset of delamination.
An analysis of the distribution of stress and deformation in fibre-reinforced composites subjected to stresses in planes normal to the fibre direction and the influence of material properties is presented. A stress concentration factor valid for all the laminae presently used in industry is also obtained.
Effect of the automation of advanced composite fabrication processes on part cost
Qualification of S-glass/epexy thermal isolator bands Bauer, J. SAMPE Journal Vol 23 No 2 (March~April 1987) pp 18-23 The precise requirements for thermal isolator tension straps which will support chargecoupled devices (operated at - 9 5 ° C - 100°C) in the Wide Field/Planetary Camera - one of the instruments to be housed in the Hubble Space Telescope, planned to orbit the earth at a nominal altitude of 310 miles - are described. The straps are made from composite materials and glass fibre-reinforced epoxy resins are shown to best meet the properties required. Further, filament-wound S-2 glass in Epon 828, is shown to have good load-carrying capacity, more precise (dimensional characteristics, and a higher spring constant than the previously-used S-109 glass.
Krolewski, S. and Gutowski, T. SAMPE Journal Vol 23 No 3 (May~June 1987) pp 21-26 An economic model which has been developed to assess the effect of automation on the cost of components and to aid in the design of new automation methods is presented. The model compares the cost of manufacturing a flat laminate using manual labour and that of producing it by automated methods. The results indicate that m a n y . current methods of advanced composite automation, with the exception of pultrusion and filament winding, are probably not cost effective. It is suggested that improvements in the cost effectiveness of automated techniques for fabricating advanced composites require the development of 'flexible' manufacturing techniques. Effects of moisture and temperature on the compressive and short beam shear properties of Fiberile T300/976 fabric
Tang, J. M. and Springer, G. S. Journal of Reinforced Plastics and Composites Vol 7 (March 1988) pp 120-135 The maximum moisture content, diffusivity, the compression strength and the short beam shear strength (SBS) of Fiberite (T300/976) fabric composites have been determined as a function of temperature and moisture. It was concluded that both moisture and temperature reduce the strength and stiffness of the composites. Drying and re-moisturising affected only the compressive strength while the SBS remained unaffected. Finite element analysis for loads distribution on multi-fastener joints
Wang, S and Hun, Y. Journal of Composite Materials Vo122 No 2 (1988) pp 124-135 A finite element method is developed and used to investigate the load distribution in multi-fastener joints. The plates are modelled by 8-node plane stress elements, the symmetric and anti-symmetric properties of the joint are used to reduce the amount of computation required. Several types of joints are analysed and the results discussed. An ideal clamping analysis for a cross-ply laminate Valisetty, R. R., Murthy, P. L. N. and Rehfield, L. W. Journal of Composite Materials Vo122 No 2 (1988) pp 136-153 The authors discuss elementary clamping models for a three layer crossply laminate. All the models discussed leave residual warping at the edges. Through further analysis, an exact interior solution is identified, corresponding to the ideal clamping. Evidence is presented for the existence of fixed edge comer singularities which affect the edge response. On the stress distribution in a luminal Cheng, S. and Chen, D. Journal of Reinforced Plastics and Composites Vol 7 (March 1988) pp 136-144
416
A sandwich layer containing an interface crack
Itou, S. Engineering Fracture Mechanics Vol 29 No 5 (1988) pp 549-555 Stresses around an interface crack in an elastic layer sandwiched between two elastic half-planes are determined. The stress intensity factors are calculated numerically for some combinations of Young's modulus ratio of the composite materials and crack length. A simplified approach for interlamlnar stresses around a hole in [0/90], I m i n a t ~
Zhang, K and Ueng, C. E. S. Journal of Composite Materials Vol 22 No 2 (1988) pp 192-202 The authors propose a simplified model with which to calculate the interlaminar stresses in a cross-ply laminate. The assumptions used in the derivation include: the distribution of in-plane stresses is uniform across the thickness of each ply, the length and width of the laminate are much larger than the hole diameter and the affected area associated with the interlaminar stresses is limited to a distance of twice the laminate thickness from the hole edge, Results show agreement with those obtained by other means. Tensile fatigue of notched carbon/epoxy specimens 'search for optimum model'
Diamantakos, C. and Fritz, R. J. Journal of Reinforced Plastics and Composites Vol 7 (March 1988) pp 165-178 The fatigue of notched specimens and the parameters influencing their behaviour have been investigated. It is concluded that although two types of equations can be employed to represent S-N data on notched specimens, further work is needed in order to establish a universal model.
METAL MA TRICES Calculating the stress/strain behaviour of uniaxial metallic composites with strainhardening components
Weiss, H. -J., Krumphold, R and Sch~idlich,
S. Composites Science and Technology Vol 30 No 1 (1987) pp 5-17 The development of an algorithm to model the response of uniaxial metal-matrix composites to non-monotonic loading is discussed. This algorithm takes the form of a flow chart for data processing to be used together with a prescription for extracting the input data from a special experimental curve. Strain hardening and the Bauschinger effect of the components is taken into account. The stress/strain curve obtained from the model is compared with that obtained from a sample of copper reinforced with high-strength steel wires and it is found that residual stresses can be determined quantitatively. It is suggested that the algorithm will be suitable for modelling low-cycle fatigue of ductile uniaxial composites Characterization of Nicalon (SIC) reinforced ainminium wire as a function of temperature Favry, Y. and Bunsell, A. R. Composites Science and Technology Vol 30 No 2 (1987) pp 85-97 The results of tensile tests on Nicalon fibre-reinforced aluminium filaments, produced as a potential semi-finished product for the manufacture of metal matrix composites, are reported and discussed. The study indicates that the full potential of the fibres is not realized due to misalignment and fibre breakage at the filament surface. There was poor bonding between fibres and matrix and the filaments would require considerable consolidation during composite manufacture. Also, above the melting point of aluminium, a reaction took place between fibre and matrix. However, the filaments exhibited good stability up to the melting point of aluminium and did not creep under tensile loading. Discontinuousiy-reinforced ainminium matrix composites Girot, F. A., Quenisset, J. M. and Naslain, R. Composite Science and Technology Vol 30 No 3 (1987) pp 155-184 This article reviews the literature (106 References) relating to studies of aluminium matrix composites reinforced with ceramic particles, short fibres, or whiskers. Topics discussed include: the nature, morphology and performances of the reinforcements; the composition of the aluminium alloys; fabrication methods; mechanical behaviour and characteristics; areas of application; and theoretical models allowing predictions of properties. It is concluded that while numerous data to assess the potential of these composites are available, mechanisms of failure such as under cyclic and impact loading are not yet clear and certain correlations such as those between fibre/matrix bonding and processing parameters cannot yet be assessed with accuracy. Effect of reinforcements on the ageing process of an AI-Cn/SiO2 AI2Oa metal matrix composite
Abis, S. and Douzelli, G. Journal of Materials Science Letters Vol 7 (1988) pp 51-52 The effect of Al20 3 -SiO2 reinforcements on the ageing process of Al-Cu/SiO2 A1203 composite has been reported. Hardness tests and differential calorimetry were performed and it is shown that the reinforcements have a strong effect on the ageing sequence.
COMPOSITES. SEPTEMBER 1988
An analysis of the distribution of stress and deformation in fibre-reinforced composites subjected to stresses in planes normal to the fibre direction and the influence of material properties is presented. A stress concentration factor valid for all the laminae presently used in industry is also obtained.
Effect of the automation of advanced composite fabrication processes on part cost
Qualification of S-glass/epexy thermal isolator bands Bauer, J. SAMPE Journal Vol 23 No 2 (March~April 1987) pp 18-23 The precise requirements for thermal isolator tension straps which will support chargecoupled devices (operated at - 9 5 ° C - 100°C) in the Wide Field/Planetary Camera - one of the instruments to be housed in the Hubble Space Telescope, planned to orbit the earth at a nominal altitude of 310 miles - are described. The straps are made from composite materials and glass fibre-reinforced epoxy resins are shown to best meet the properties required. Further, filament-wound S-2 glass in Epon 828, is shown to have good load-carrying capacity, more precise (dimensional characteristics, and a higher spring constant than the previously-used S-109 glass.
Krolewski, S. and Gutowski, T. SAMPE Journal Vol 23 No 3 (May~June 1987) pp 21-26 An economic model which has been developed to assess the effect of automation on the cost of components and to aid in the design of new automation methods is presented. The model compares the cost of manufacturing a flat laminate using manual labour and that of producing it by automated methods. The results indicate that m a n y . current methods of advanced composite automation, with the exception of pultrusion and filament winding, are probably not cost effective. It is suggested that improvements in the cost effectiveness of automated techniques for fabricating advanced composites require the development of 'flexible' manufacturing techniques. Effects of moisture and temperature on the compressive and short beam shear properties of Fiberile T300/976 fabric
Tang, J. M. and Springer, G. S. Journal of Reinforced Plastics and Composites Vol 7 (March 1988) pp 120-135 The maximum moisture content, diffusivity, the compression strength and the short beam shear strength (SBS) of Fiberite (T300/976) fabric composites have been determined as a function of temperature and moisture. It was concluded that both moisture and temperature reduce the strength and stiffness of the composites. Drying and re-moisturising affected only the compressive strength while the SBS remained unaffected. Finite element analysis for loads distribution on multi-fastener joints
Wang, S and Hun, Y. Journal of Composite Materials Vo122 No 2 (1988) pp 124-135 A finite element method is developed and used to investigate the load distribution in multi-fastener joints. The plates are modelled by 8-node plane stress elements, the symmetric and anti-symmetric properties of the joint are used to reduce the amount of computation required. Several types of joints are analysed and the results discussed. An ideal clamping analysis for a cross-ply laminate Valisetty, R. R., Murthy, P. L. N. and Rehfield, L. W. Journal of Composite Materials Vo122 No 2 (1988) pp 136-153 The authors discuss elementary clamping models for a three layer crossply laminate. All the models discussed leave residual warping at the edges. Through further analysis, an exact interior solution is identified, corresponding to the ideal clamping. Evidence is presented for the existence of fixed edge comer singularities which affect the edge response. On the stress distribution in a luminal Cheng, S. and Chen, D. Journal of Reinforced Plastics and Composites Vol 7 (March 1988) pp 136-144
416
A sandwich layer containing an interface crack
Itou, S. Engineering Fracture Mechanics Vol 29 No 5 (1988) pp 549-555 Stresses around an interface crack in an elastic layer sandwiched between two elastic half-planes are determined. The stress intensity factors are calculated numerically for some combinations of Young's modulus ratio of the composite materials and crack length. A simplified approach for interlamlnar stresses around a hole in [0/90], I m i n a t ~
Zhang, K and Ueng, C. E. S. Journal of Composite Materials Vol 22 No 2 (1988) pp 192-202 The authors propose a simplified model with which to calculate the interlaminar stresses in a cross-ply laminate. The assumptions used in the derivation include: the distribution of in-plane stresses is uniform across the thickness of each ply, the length and width of the laminate are much larger than the hole diameter and the affected area associated with the interlaminar stresses is limited to a distance of twice the laminate thickness from the hole edge, Results show agreement with those obtained by other means. Tensile fatigue of notched carbon/epoxy specimens 'search for optimum model'
Diamantakos, C. and Fritz, R. J. Journal of Reinforced Plastics and Composites Vol 7 (March 1988) pp 165-178 The fatigue of notched specimens and the parameters influencing their behaviour have been investigated. It is concluded that although two types of equations can be employed to represent S-N data on notched specimens, further work is needed in order to establish a universal model.
METAL MA TRICES Calculating the stress/strain behaviour of uniaxial metallic composites with strainhardening components
Weiss, H. -J., Krumphold, R and Sch~idlich,
S. Composites Science and Technology Vol 30 No 1 (1987) pp 5-17 The development of an algorithm to model the response of uniaxial metal-matrix composites to non-monotonic loading is discussed. This algorithm takes the form of a flow chart for data processing to be used together with a prescription for extracting the input data from a special experimental curve. Strain hardening and the Bauschinger effect of the components is taken into account. The stress/strain curve obtained from the model is compared with that obtained from a sample of copper reinforced with high-strength steel wires and it is found that residual stresses can be determined quantitatively. It is suggested that the algorithm will be suitable for modelling low-cycle fatigue of ductile uniaxial composites Characterization of Nicalon (SIC) reinforced ainminium wire as a function of temperature Favry, Y. and Bunsell, A. R. Composites Science and Technology Vol 30 No 2 (1987) pp 85-97 The results of tensile tests on Nicalon fibre-reinforced aluminium filaments, produced as a potential semi-finished product for the manufacture of metal matrix composites, are reported and discussed. The study indicates that the full potential of the fibres is not realized due to misalignment and fibre breakage at the filament surface. There was poor bonding between fibres and matrix and the filaments would require considerable consolidation during composite manufacture. Also, above the melting point of aluminium, a reaction took place between fibre and matrix. However, the filaments exhibited good stability up to the melting point of aluminium and did not creep under tensile loading. Discontinuousiy-reinforced ainminium matrix composites Girot, F. A., Quenisset, J. M. and Naslain, R. Composite Science and Technology Vol 30 No 3 (1987) pp 155-184 This article reviews the literature (106 References) relating to studies of aluminium matrix composites reinforced with ceramic particles, short fibres, or whiskers. Topics discussed include: the nature, morphology and performances of the reinforcements; the composition of the aluminium alloys; fabrication methods; mechanical behaviour and characteristics; areas of application; and theoretical models allowing predictions of properties. It is concluded that while numerous data to assess the potential of these composites are available, mechanisms of failure such as under cyclic and impact loading are not yet clear and certain correlations such as those between fibre/matrix bonding and processing parameters cannot yet be assessed with accuracy. Effect of reinforcements on the ageing process of an AI-Cn/SiO2 AI2Oa metal matrix composite
Abis, S. and Douzelli, G. Journal of Materials Science Letters Vol 7 (1988) pp 51-52 The effect of Al20 3 -SiO2 reinforcements on the ageing process of Al-Cu/SiO2 A1203 composite has been reported. Hardness tests and differential calorimetry were performed and it is shown that the reinforcements have a strong effect on the ageing sequence.
COMPOSITES. SEPTEMBER 1988