- Email: [email protected]
Morphology of high modulus carbon fibres
Abstracts of journals Compiled by Dr H. A. Barker, L Bell, B. Gill and R. Warren, Department of Metallurgy and Materials Technology, University of Surrey, Gu#dford, England GENERAL A capability and limitation study of thermography of carbon-carbon cones
of twisting needed but leads to instability. A three component composite wire has therefore been investiga,ted but with unsatisfactory results.
Stiefeld, B. and Yoshimura, R. H.
Materials Evaluation, Vol 29, No 12, p 281 (December 1971) T h e use of thermal transducer and of infra-red scanning camera techniques for the detection of flaws in carboncarbon cones has been studied. T h e results correlate well with other ndt procedures such as eddy current tests. T h e developmen.t of a digitizing system to produce computer-compaUble resuits has added to the capability of the system. Changes in the properties of carbon fibres during fast neutron irradiation
Peggs, I. D. Nature (Physical Science),
Vol 235, No 58, p 112 (7 February 1972)
F o r several different types of carbon fibre it has been found that fast neutron irradiation causes a degradation in structure followed by an apparent recrystallization process. Mechanical properties worsen, then improve, the content of each change being very dependent on temperature. T h e magnitude of 'lattice strain' was also observed to increase and then decrease with irradiation, the turning point corresponding to that found for the other parameters. The conductivity of cermets and other mnltiphase materials: Part I. Theoretical considerations concerning the electrical resistivity as a function of concentration and stereometry (in German)
Ondracek, G. and Schulz, B. Berichte der Deutschen Keramischen Gesellscha[t, Vol 48, No I0, pp 427-434 (October 1971) A review is given of the many theoretical equations which have been derived to allow calculation of the field properties (electrical resistivity, thermal conductivity, etc) of muhiphase materials as a function of the proportion and spatial configuration of the constituent phases. T h e equations are presented generally, as well as being related specifically to electrical resistivity. Attention is also given to their application to porous materials. Design problems composites
of
superconducting
Critchlow, P. R. Journal of Applied
Physics, Vol 42, No 11, p 1506 (October 1971) In designing muhifilamentary superconducting wires it is necessary to reduce transverse currents between filaments. W h e n a copper matrix is used the wire is twisted to achieve this. T h e use of cupronickel reduces the degree
142
COMPOSITES May 1972
Effect of surface damage on the strength of c-axis sapphire filaments
Crane,
R. L. and
Tressler, R. E.
Journal of Composite Materials, Vol 5, p 537 (October 1971) An investigation on the effect of abrasion on the strength of Saphikon filaments has been carried out to assess their usefulness in reinforced metal technology. It was observed that selfabrasion which red.uces the room temperature strength to 200 000 psi does not affect the high temperature strength (at 1100 and 1300°C). It was also concluded that Ni-Cr reinforced with over 50 vol% of c-axls sapphire filament would not be competitive with existing directionally solidified eutectics such as NisA1-Ni3Cb. Fatigue fracture in the subchondral bone
Freeman, M. A. R., Day, W. H. and Swanson, S. A. V. Medical & Biological
Engineering, Vol 9, No 6, pp 619-629 Strains occurring in the subchondral bone plate around the margins of the articular surface of the femoral head were measured when the femoral head was subjected to a physiological load firstly without and then with defects in the bone within the head. Stresses calculated from these measured strains were compared with stresses known to cause fatigue fractures in bone. F o r the intact femoral head it would be unlikely that the strains would cause fatigue fracture of the subchondral bone in life but when a cylindrical defect 13ram long, and of 10mm diameter, was made in the centre of the femoral head to simulate a cyst. the measured strains were high enough to lead to fatigue fracture. T h e r e is a possibility that revascularization of the overlying cartilage could result. Further study of composite lamiFnates under cylindrical bending
Pagano, N.
J. and Wang, A. S. D.
Journal of Composite Materials, Vol 5, p 521 (October 1971) This article is one of a series devoted to an investigation of the range of applicability of classical laminated plate theory to composite laminates under static bending. This particular paper is an extension of the problem to include applied loads of more general distribution. It is concluded that warping of 'the cross section is worse for a 3-ply laminate than for a single layer and that uniformly loaded laminates exhibit more severe warping at the ends.
Intrinsic strength and mm-Hookcan behaviour of carbon fibres
Jones, W. R. and Johnson, J. W.
Carbon, Vol 9, No 5, pp 645-656 (October 1971) T h e Sinclair loop test, in which only a small volume of material is stressed to failure, has been used to evaluate the intrinsic strength and the stressstrain characteristics of both high strength and high modulus PAN-based carbon fibres. High strength fibres, ie those prepared by pyrolysis to temperatures less than 1600"C, are elastic to fracture and, in the absence of flaws. are capable of deseloping a fracture strength of 10"lbf/in '. High modulus fibres on the other hand show a marked non-linear behaviour at strains greater than about 0-5% with a decrease in Young's modulus with increasing strain. This non-Hookean behaviour is apparently the result of structural failure of the fibre in the compressive region under the action of the high compressive forces set up due to bending and its own great structural anisotropy. Macroscopic fracture mechanics advanced composite materials
of
Waddoups, M. E., Eisenmann, J. R. and Kaminski, B. E. Journal of
Composite Materials, Vol 5, pp 446454 (October 1971) T h e application of classical fracture mechanics to laminated composites is discussed. A convenient method is proposed for predicting the static strength of a flawed specimen. Theoretical predictions are compared with experimental data for specimens containing two types of flaw. Measurements of the elastic modnii of laminated composites using aa ultrasonic technique
Tauchert, T. R. and Giizelsu, A. N.
Journal o] Composite Materials, Vol 5, pp 549-552 (October 1971) A description is given of the measuremerit of the elastic moduli of some woven fabric laminates of the type commonly used for thermal insulation. Limitations in the accuracy of this method are pointed out. Morphology of high modulus carbon fibres
Stewart,
M.
and
Feughelman,
M.
Nature, Vol 235, No 5336, p 274 (4 February 1972) T h e existence of sheet-like elements arranged concentric to the fibre axis has been confirmed for PAN-based high modulus carbon fibres using a J E O L JSM-2 scanning electron microscope. T h e sheet thickness was of the order of 1000A. Failure in torsion resulted in breakdown of the fibre into i.ts sheetlike units. Nomograms for calculating the properties of reinforced fiber materials
Karl?inos, D. M. and Kadyrov, V. Kh.
Sovtet Powder Metallurgy and Metal Ceramics, Vol 10, No 6, pp 492-49.5 (June 1971) Nomograms are derived and presented for the determination of: (1) the addi-
of twisting needed but leads to instability. A three component composite wire has therefore been investiga,ted but with unsatisfactory results.
Stiefeld, B. and Yoshimura, R. H.
Materials Evaluation, Vol 29, No 12, p 281 (December 1971) T h e use of thermal transducer and of infra-red scanning camera techniques for the detection of flaws in carboncarbon cones has been studied. T h e results correlate well with other ndt procedures such as eddy current tests. T h e developmen.t of a digitizing system to produce computer-compaUble resuits has added to the capability of the system. Changes in the properties of carbon fibres during fast neutron irradiation
Peggs, I. D. Nature (Physical Science),
Vol 235, No 58, p 112 (7 February 1972)
F o r several different types of carbon fibre it has been found that fast neutron irradiation causes a degradation in structure followed by an apparent recrystallization process. Mechanical properties worsen, then improve, the content of each change being very dependent on temperature. T h e magnitude of 'lattice strain' was also observed to increase and then decrease with irradiation, the turning point corresponding to that found for the other parameters. The conductivity of cermets and other mnltiphase materials: Part I. Theoretical considerations concerning the electrical resistivity as a function of concentration and stereometry (in German)
Ondracek, G. and Schulz, B. Berichte der Deutschen Keramischen Gesellscha[t, Vol 48, No I0, pp 427-434 (October 1971) A review is given of the many theoretical equations which have been derived to allow calculation of the field properties (electrical resistivity, thermal conductivity, etc) of muhiphase materials as a function of the proportion and spatial configuration of the constituent phases. T h e equations are presented generally, as well as being related specifically to electrical resistivity. Attention is also given to their application to porous materials. Design problems composites
of
superconducting
Critchlow, P. R. Journal of Applied
Physics, Vol 42, No 11, p 1506 (October 1971) In designing muhifilamentary superconducting wires it is necessary to reduce transverse currents between filaments. W h e n a copper matrix is used the wire is twisted to achieve this. T h e use of cupronickel reduces the degree
142
COMPOSITES May 1972
Effect of surface damage on the strength of c-axis sapphire filaments
Crane,
R. L. and
Tressler, R. E.
Journal of Composite Materials, Vol 5, p 537 (October 1971) An investigation on the effect of abrasion on the strength of Saphikon filaments has been carried out to assess their usefulness in reinforced metal technology. It was observed that selfabrasion which red.uces the room temperature strength to 200 000 psi does not affect the high temperature strength (at 1100 and 1300°C). It was also concluded that Ni-Cr reinforced with over 50 vol% of c-axls sapphire filament would not be competitive with existing directionally solidified eutectics such as NisA1-Ni3Cb. Fatigue fracture in the subchondral bone
Freeman, M. A. R., Day, W. H. and Swanson, S. A. V. Medical & Biological
Engineering, Vol 9, No 6, pp 619-629 Strains occurring in the subchondral bone plate around the margins of the articular surface of the femoral head were measured when the femoral head was subjected to a physiological load firstly without and then with defects in the bone within the head. Stresses calculated from these measured strains were compared with stresses known to cause fatigue fractures in bone. F o r the intact femoral head it would be unlikely that the strains would cause fatigue fracture of the subchondral bone in life but when a cylindrical defect 13ram long, and of 10mm diameter, was made in the centre of the femoral head to simulate a cyst. the measured strains were high enough to lead to fatigue fracture. T h e r e is a possibility that revascularization of the overlying cartilage could result. Further study of composite lamiFnates under cylindrical bending
Pagano, N.
J. and Wang, A. S. D.
Journal of Composite Materials, Vol 5, p 521 (October 1971) This article is one of a series devoted to an investigation of the range of applicability of classical laminated plate theory to composite laminates under static bending. This particular paper is an extension of the problem to include applied loads of more general distribution. It is concluded that warping of 'the cross section is worse for a 3-ply laminate than for a single layer and that uniformly loaded laminates exhibit more severe warping at the ends.
Intrinsic strength and mm-Hookcan behaviour of carbon fibres
Jones, W. R. and Johnson, J. W.
Carbon, Vol 9, No 5, pp 645-656 (October 1971) T h e Sinclair loop test, in which only a small volume of material is stressed to failure, has been used to evaluate the intrinsic strength and the stressstrain characteristics of both high strength and high modulus PAN-based carbon fibres. High strength fibres, ie those prepared by pyrolysis to temperatures less than 1600"C, are elastic to fracture and, in the absence of flaws. are capable of deseloping a fracture strength of 10"lbf/in '. High modulus fibres on the other hand show a marked non-linear behaviour at strains greater than about 0-5% with a decrease in Young's modulus with increasing strain. This non-Hookean behaviour is apparently the result of structural failure of the fibre in the compressive region under the action of the high compressive forces set up due to bending and its own great structural anisotropy. Macroscopic fracture mechanics advanced composite materials
of
Waddoups, M. E., Eisenmann, J. R. and Kaminski, B. E. Journal of
Composite Materials, Vol 5, pp 446454 (October 1971) T h e application of classical fracture mechanics to laminated composites is discussed. A convenient method is proposed for predicting the static strength of a flawed specimen. Theoretical predictions are compared with experimental data for specimens containing two types of flaw. Measurements of the elastic modnii of laminated composites using aa ultrasonic technique
Tauchert, T. R. and Giizelsu, A. N.
Journal o] Composite Materials, Vol 5, pp 549-552 (October 1971) A description is given of the measuremerit of the elastic moduli of some woven fabric laminates of the type commonly used for thermal insulation. Limitations in the accuracy of this method are pointed out. Morphology of high modulus carbon fibres
Stewart,
M.
and
Feughelman,
M.
Nature, Vol 235, No 5336, p 274 (4 February 1972) T h e existence of sheet-like elements arranged concentric to the fibre axis has been confirmed for PAN-based high modulus carbon fibres using a J E O L JSM-2 scanning electron microscope. T h e sheet thickness was of the order of 1000A. Failure in torsion resulted in breakdown of the fibre into i.ts sheetlike units. Nomograms for calculating the properties of reinforced fiber materials
Karl?inos, D. M. and Kadyrov, V. Kh.
Sovtet Powder Metallurgy and Metal Ceramics, Vol 10, No 6, pp 492-49.5 (June 1971) Nomograms are derived and presented for the determination of: (1) the addi-