Abstracts Compiled by Dr H. A. Barker, I. Bell, B. Gill and R. Warren, Department of Metallurgy and Materials Technology, University of Surrey, Guildford.
Copies o f original articles are best obtained by writing directly to the journal in which they appeared. The addresses o f journals can be found in 'World list o f scientific and technical publications" 'Willings press guide; 'Newspaper press directory" and for A m erican journals only, 'Ay ers:
Ceramic matrices GRIMER, F. J. and ALl, M. A. The strengths of cements reinforced with glass fibres
Magazh~e o f Concrete Research, 21, No 66, p 23 (March 1969) The results of a programme to develop a glass fibre reinforced cement for the building industry are presented. Evaluation tests with E glass in portland, superphosphated and high alumina cements have been carried out. Fabrication o f . the composites was effected bY spraying a cement slurry, chopped fibre mixture onto glass fibre rovings and compacting in a suction mould. Density decreased as fibre content was increased. The reinforced concretes showed increases in modulus of rupture and tensile strength of 2 to 4 and 10 to 30 times that o f the matrix respectively. The decrease in strength which was observed after 5 to 30 days, presumably due to chemical attack, is expected to be eliminated by use o f a new alkalic resistant glass currently being developed. (69/2/7) HASSLEMAN, D. P. H. Griffith criteria and thermal shock resistance of single phase versus multiphase brittle ceramics
Journal o f the American Ceramic Society, 52, No 5, p 288 (May 1969} By a mathematical arguement it is shown that the extent of crack propagation due to thermal shock is independent o f any material property. Thus avoidance o f crack initiation by maximising thermal shock resistance may not be sufficient under severe thermal shock conditions. It is pointed
out that crack propagation is much reduced in, for example, porous ceramics and refractory carbides containing a dispersed graphite phase, and the suggestion is made that heterogenous ceramics should have higher thermal shock resistance than single phase ceramics. (69/2/8)
ROSSI, R. C. Thermal expansion of BeO-SiC composites
Journal o f the American Ceramic Society, "52, No 5, p 290 - 291 (May 1969) The linear thermal expansion o f BeOSiC composites was measured from room-temperature up to 1000°C. The effect of the composition o f the composite on the thermal expansion was found not to agree with that predicted theoretically. For the BeOrich composites, this deviation was attributed to micro-cracks which were observed by electron microscopy and which probably .formed during the fabrication process. For the SiC-rich composites the deviation was attributed to voids Which formed around the BeO particles as a result of their shrinkage during cooling after the fabrication of the composites. (69/2/9)
M e t a l matrices KELLY, A. and LILHOLT, H. Stress-strain curve of a fibre-reinforced composite
Philisophical Magazine, 20, No 164, p 311 (August 1969) Examination of the stress-strain curves of composites of thin tungsten wires
aligned in copper shows that at strains greater than the yield strain o f copper the stresses in the matrix are higher than those .given by the law of mixtures. The effect is attributed to constraints due to differences in lateral contraction tendency of fibre and matrix since it is found to disappear once the fibres have yielded. The observed stresses a r e found to be higher than those predicted for a completely plastic matrix and this is thought to mean that even in stage 2 of the curve for the composites much of the matrix still deforms elastically. (69/3/I 3) KIRKPATRICK, M. E., STANDHAMMER, K. P., REGER, J., L, and TOY, A.
A continuous process for the production of whisker reinforced composites Journal o f Composite Materials, 3, p 322, (April 1969} A p r o t o t y p e system for the continuous dielectrophoretic deposition and alignment of micron size, ultra high strength whiskers is described which consists of deposition on to one of two electrodes placed in a suspension of whiskers on the application of a voltage. The metal foils on which the aligned whiskers are deposited arc sandwiched and consolidated by hot pressing and diffusion bonding. Preliminary mechanical properties of selected composite compositions are presented and discussed and the feasibility of continuous production of metal matrix composites by this method is shown. (69/3/14) KREIDER, K. and MARCIANO, M. Mechanical properties aluminium composites
Tr a n sactions A IME, 1279 - 1286 (June 1969)
An investigation was made o f the mechanical properties o f composites made up of SiC-coate'd boron fibres in an AI matrix. The composites were prepared by plasma spraying single layers of fibres with AI and then diffusion-bonding the layers together. Properties were measured as functions of temperature and fibre orientation in composites which contained up to 50% fibre. The elastic properties, in the reinforced direction, were found to agree with t h e rule of mixtures. M ultidirectionally-reinforced compos-. ites were also tested. (69/3/15)
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