High temperature strength of boron, silicon carbide coated boron, silicon carbide, stainless steel and tungsten fibres

High temperature strength of boron, silicon carbide coated boron, silicon carbide, stainless steel and tungsten fibres

Abstracts of journals Compiled by Dr 14. A. Barker, I. Bell, B. Gill and R. Warren, Department of Metallurgy and Materials Technology, University of S...

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Abstracts of journals Compiled by Dr 14. A. Barker, I. Bell, B. Gill and R. Warren, Department of Metallurgy and Materials Technology, University of Surrey, Guildford, England

Copies o[ original articles are best obtained by writing directly to the journal in which they appeared. The addresses o] journals can be ]ound in 'World list o[ scientific periodicals', "Willings press guide', 'Newspaper press directory' and [or American journals only, 'N. W. Ayer' s directory of newspapers and periodicals'.

GENERAL Analysis of the work of fracture of fibrous materials Harrison, N. L. Fibre Science and

Technology, Vol 4, No 1, p 37 (July 1971) It as shown mathematically that replacement of the term which represents the energy dissipated in the formation of a unit area of crack by the sum of the loss in strain energy of the system after the fibre breaks and the energy dissipation by other mechanisms enables linear fracture mechanics to be applied to fibrous materials. A g e n e r a l f o r m u l a for the former is derived which is applicable to a wide spectrum of materials. (71/1/86) Breakthrough in tough composites Livesey, R. The Engineer, Vol 33, No

6, p 19 (15 July 1971) It is proposed that the disadvantages of both high and low bond strengths between fibre and matrix in composites may be overcome by the use of a two component fibre. Such a fibre would have an outer sheath to give a high strength b o n d with the matrix and an inner sheath which is only weakly bonded to the outer. T h e strong outer bond should provide high shear a n d transverse strength while crack propagation should be halted by the inner element as it debonds from the sheath. An example of the properties of such a composite is given and briefly discussed. (71 / 1/ 87) Carbcm-fibre / nickel compatibility Barclay, R. B. and Bonfield,

W.

Journal oI Materials Science, Vol 6~ No 8, pp 1076-1083 (August 1971) T h e effects of evaporated pure nickel coatings on the room-temperature strength and microstructure of individual high-modulus carbon fibres are described. T h e fibre fracture strength is not affected by vacuum-annealing the coated fibres at 1 0 - ' m m H g pressure and up to 1100°C. It is, however, degraded by annealing in air at

this temperature and strength reduction is dependent on time and temperature of anneal but independent of coating thickness. T h e strength reduction is not related to recrystallization within the fibre b u t to the dissolution of carbon in the nickel coating. (71 / 1/ 88) Carbon fibres obtained by thermal decomposition of vapourized hydrocarbon goyam, T., Endo, M. and Murayama,

S. Proceedings, 14th Japan Congress on Materials Research, Kyoto, pp 96-98 (1971) Fibres of 3-100gm diameter and 15-20 cm long have been grown on a graphite substrate at about 1200°C by thermal decomposition of a vapourized hydrocarbon such as benzene. Scanning electron micrographs show a rolled sheet structure. T h e tensile strengths varied from 0.5 to 2.5 G N / m ' , (71/1[89) Composite materials Gibbons, B. and

Greig,

R.

H.

Engineering Materials and Design, Vol 14, No 8, pp 783-786 (September 1971) T h e history of the development of reinforced plastics is given very briefly. This is followed by a discussion of the concept of composite materials and the k i n d of product that is now available to designers. Various new developments and problems and limitations of these materials are dealt with. (71/1/90) Controlled solidification of the eutectic LiF-MgF~ Bright, M. W. A. and Lewis, M. H.

Journal of Materials Science, Vol 6, No 7, pp 1012-1020 (July 1971) A two-phase 'model' composite material ~of LiF and MgF= has been prepared by unidirectional solidification of the mixed eutectic flouride. T h e morphology, revealed by optical and electron microscopy, is One of regularly-arranged rods of the MgF, phase in a continuous LiF matrix. (71/1/91)

Discovery makes earboa fibre 'cheap as glass' Peters, D. The Engineer, p 27 (29

April 1971) A process in which the complex oxidation of precursor fibres is replaced by chemical pretreatment thereby allowing a cheap grade of rayon to be used could make carbon fibre economically competitive with some high grade glass fibres. After pretreatment the fibres are heated in an inert atmosphere until sufficiently carbonized to take an electric current. A temperature of 2273 K is maintained for 30 sec and after a total heating time of about 3 r a i n the fibres are allowed to cool. (71/1/92) Electron microscope study of the microstructure of carbon and graphite fibers from a rayon precursor Bacon, R. and Silvazzi, A. F. Carbon,

Vol 9, No 3, pp 321-325 (May 1971) Structural observations, using both transmission and surface-replication electron microscopy, reinforce the fibre structure proposed by R u l a n d and co-workers, consisting of long ribbon-like layers of turbostraticallypacked graphite layer planes arranged in fibrils. These fibrils probably derive from the structure of the rayon precursor fibre. (71/1/93) High temperature strength of boron, silicon carbide coated boron, silicon carbide, stainless steel and tungsten fibres Veltri, R. D. and Galasso, F. S.

Journal o[ the American Ceramic Society, Vol 54, No 6, p 319 (June 1971) In order to make full use of high modulus, low density fibres for high temperature composites the results of the characterization of several types of fibre are presented concisely in two graphs. In these are shown the ultimate tensile strengths at temperatures from 0°C to 1000°C in air and in argon of fibres of boron, SiC-coated boron, stainless steel, tungsten and SiC fibres. These studies showed that of the fibres examined, only SiCcoated boron and SiC-fibres could be

COMPOSITES December 1971

25~

used in composites at temperatures of up to 1000°C in air. T h e advantages that might be realized from other fibres if oxidation were to be prevented are readily seen from the graphs. (71 / 1/94) Making the most of carbon fibre

Mortimer, J. The Engineer, p 26 (24

June 1971) T h e types of carbon fibre and resin available are examined and the methods of using them in current engineering practice are discussed. T h e roles of carbon fibres in shafting and blading in general and in the development of the RB211 in particular are discussed. (71/1/95) The mechanical performance of cromplied composites

Lavengood,

R.

E.

and

Ishai,

O.

Polymer Engineering and Scie~nce, Vol 11, No 3, p 226 (May 1971) T h e tensile behaviour of glass-fibre/ epoxy cross-plied laminates was investigated for both brittle and ductile matrices and it was found that in both types of of system the laminae showed higher strength, stiffness and toughness than equivalent unidirectional composites. In the case o f 90°-0 ° systems the use of a ductile matrix resulted in a marked increase in strength with only a slight decrease in stiffness with the initial cracking stress nearly doubled. This could mean that a t virtually no extra cost the usable strength would be doubled for some applications. (71/1 ]96) Mechanical properties of stressgraphitized carbon libers: thermally induced relaxation and recovery

Shrian, S. and Strong, S. L. Fibre

Science and Technology, Vol 4, No 1, p 67 (July 1971) High modulus carbon fibres produced from a rayon precursor by stretching at high temperatures showed changes i n dimensions and properties when heated above 700°(3 without an externally applied stress. Low temperature annealing was found to induce structural changes by reason of a relaxation in the graphite layer planes with an accompanying reduction in mechanical property values. Stress-graphitized fibres subjected to further h e a t i n g above 2400°C were found to undergo further graphitization and to become stabilized. (71/1/97)

Plasticity and initiation of fracture in crystals with non-deforming inclusions

Tanaka, K., Mori, T. and Nakamura,

T. Proceedings, 14th Japan Congress on Materials Research, Kyoto, pp 52-56 (1971) Non-deforming inclusions such as particles or fibres of a strong material can be used to reinforce metals. From theoretical considerations of the elastic state and thermodynamic stability of such composites expressions are derived for the work hardening behaviour and fracture initiation of the material. (71 / 1/ 99)

Pultrusion - - a growing topnage market for reinforced plastics end products

Brandt Galsworthy, W. Reinforced Plastics, Vol 15, No 6, p 134 (June 1971) T h e progress of pultrusion is traced and the technical aspects of radio frequency curing are examined in view of its influence on the development of the process. It is concluded that the process will he a strong contender in the market for structural rofiles principally because the very igh pressures needed to form large cross sections in traditional materials such as metals are not required in pultrusion. (71/1 / 100)

~

A new method is proposed for testing FRP. This involves simultaneous recording of sonic vibrations at various selected points and measurement of strain by suitably situated strain gauges. T h e test sample in this case was a closed cylinder filled with water under pressure. A theory is developed to predict its behaviour and a number of experiments have been carried out. Both 'sona-graph' and 'voice-print' type recordings have been made. More work is needed but wide future applications are foreseen. (71/1/103) A tension test for filamentary composites

Hancock, J. R. and Swanson, G. D.

Journal o] Composite Materials, Vol 5, pp 414-416 (July 1971) A description of a tensile test using a simple specimen rectangular crosssection. This test achieves accurate specimen alignment and failure in the gauge-length providing a valid test with economically small specimens. (71/1/104)

Mool,

D.

and

Stephenson,

R.

Materials Evaluation, Vol 29, No 7, pp 159-164 (July 1971)

Thorue, D.

T h e ability o f through-transmitted ultrasound to detect defects in a 10ply unidirectional b o r o n / e p o x y laminate bonded to aluminium face sheets was tested. Ultrasonic C-scans showed such defects. A variety of different faults w o u l d be detected and the technique is apparently an effective inspection method for this particular composite. (71/1 / 105)

J. and Price, A. J. Fibre Science and Technology, Vol 4, No 1, p 9 (July 1971) T w o types of carbon fibre were prepared from commercial acrylic fibre by oxidation in air and inert atmosphere pyrolysis at 1273 K in one case and in the other by the use of an additional treatment at 2773 K. Measurements of the reactivity of these fibres to oxidation by carbon dioxide were made by weight loss and showed that whilst the activation energies for the reaction was the same in both cases the fibres pyrolysed at 1273 K were approximately seven times as reactive as those subsequently heat treated at 2773 K. General surface smooth, ing and the development of an extensive micro-pore system was noted. (71/1 / 101)

Hagemaier, D. J., McFaul, H. J. and Moon, D. Materials Evaluation, Vol

Cline, H. E. Acta MetaUurgica, Vol

29, No 6, pp 133-140 (]u~e 1971)

In order to predict the stability and coarsening mechanisms in eutectic alloys, the growth of shape instabilities in a rod composite is calculated assuming that interface migration is driven by capillarity and controlled by diffusion in the matrix. It is shown that coarsening may occur by ,fault migration and annihilation but the effects of. interface kinetics, surface energy anisotropy and stress are also considered. (71 / 1/ 102)

COMPOSITES December 197i

Proceedings, 14th Japan Congress on Materials Research, Kyoto, pp 115119 (1971)

Reactivity of carbon fibres to oxidation by carbon dioxide

Shape instabilities of eutectic composites at elevated temperatures

256

Fujii, T., Mizukawa, K. and Zako, M.

Ultrasonic inspection of a boron/epoxyaluminium composite panel

Non-destructive testing of graphite fiber composite strucfures

T h e ndt o f three graphite fibre composite aircraft components is described. T h e ways in which radiographic and ultrasonic testing were used as positive checking methods are described in detail for each component. T h e feasibility o f using acoustic emission tests and thermal or infra-red tests was also studied. T h e kinds of fault for which each method is most effective are listed. (71/1/98)

The study of a non-destructiott testing method of fibreglass reinforced plastics (FRP) (acoustic method)

19, No 6, p 481 (June 1971)

Vibration response: a non-destructive test for fatigue crack damage in filament-reinforced composites

Schultz, A. B. and Warwick, D. N.

Journal of Composite Materials, Vol 5, pp 394-404 (July 1971) Laminated, filament-reinforced epoxy beam specimens were fatigued in vibratory flexure. The complex modulus was measured periodically as fatigue c r a c k damage accumulated. Changes in the modulus correlated well with the amount of crack damage. Measurement of these vibration response changes shows promise as a means of non-destructive monitoring of the integrity of a composite structural member during service. (71/1/106) Viscoelastic system

stresses

in

a

composite

Hackett, R. M. Polymer Engineering and Science, Vol 11, No 3, p 220 (May 1971) An analysis of the stress distribution is presented for a composite material in which one of the components exhibits time dependent properties. Examination of the mathematical