The effect of an electric field on the solidification of off-eutectics tin/iea.d composite alloys Warner, J. C. and Verhoeven, J. D. Journal o f Materials Science, Vol 8, No 12 (Dec 1973)pp 1817-1822 The influence of an electric field upon the directional solidification of hypoand hyper-etutecticSn/Pb composite alloys was studied and equations have been derived to account for the effects of electro transport of solute in the liquid upon the solid composite composition. Electrotransport shows limited promise as a method of control of the volume fraction fibre phase in the preparation of aligned composites by directional solidification. Matrix strengthening in continuous
fibre reinforced composites under monotonic and cyclic loading Lee, R. E. and Harris, S. J. Journal of Materials Science, Vol 9 No 3 (Mar 1974) pp 359-368 Continuous tungsten fibre reinforced copper composites with fibre diameters of 11 to 48 gm (at constant volume fraction Of 0.37) were subjected to unidirectional and cyclic tensile tests. In the tensile tests, a positive deviation from rule-of-mixtures was observed, the strength increasing with interfibre spacing. This matrix strengthening was shown to be related in part to matrix grain-size. In the cyclic tests, the strengthening was greater than for the tensile tests and could be accounted for by the formation of a substructure during cycling of approximately 0.5/~m cell size. The temperature-dependence of the mechanical properties of unidirectionally solidified silver/germanium eutectic Krummheuer, W. R. and Alexander, H. Journal of Materials Science, Vol 9No 2 (Feb 1974) pp 229-239 The unidirectionally-solidified As/Ge eutectic has been investigated by dynamic tensile deformation and by light and scanning electron microscopy. Tensile tests were carried out over the range of temperatures 0-615°C and two temperature-dependent processes had to be considered to explain the results, that of increasing germanium ductility and decreasing interface shear strength with increasing temperature. Below 400°C, composite fracture is initiated by fracture of the platelets whereas, at higher temperatures, the matrix fails first.
COMPOSITES. NOVEMBER 1974
RESIN MA TRICES
Composites formed by interstitial polymerisation of vinyl monomers in polyurethane elastomers: 3. The role of graft copolymerisation Alen, G., Bowden, M. J. and Lewis, G. Polymer, Vol 15, No 1 (Jan. 1974) pp 17-18 Graft copolymerisation does not contribute to the high impact strength of composites prepared by interstitial polyurethane elastomer gels, in contrast to conventional rubber modified thermoplastics. Impact strength was reduced by incorporation of poly (1, 2-butadiene) into the backbone chain although grafting does seem to occur in this case. The drop is attributed to increased Tg.
Composites formed by interstitial polymerisation of vinyl monomers in polyurethane'elastomers: 4. Prepraration, properties and structure of acrylonitrile and styrene based composites Allen, G. et al. Polymer, Vol 15, No 1 /Jan 1974) pp 19-27 The interstitial polymerisation of acrylonitrile in polyurethane and styrene in polyurethane are described. Styrene presents more difficulties than acrylonitrile but composites based on the latter are as easily prepared as mma composites described in parts 1 and 2. The pan/pu composites have the best combination of properties and are comparable with abs. The morphology of pmma, pan, and ps is similar, each having a pu matrix and with polyvinyl domains.
Composites formed by interstitial polymerisation of vinyl monomers in polyurethane elastomers: 5. Variation, of modulus with composition Allen, G. et al. Polymer, Vol 15, No 1 (Jan 1974) pp 28-36 The experimental stress/strain data for shear loading are compared with theoretical predictions. The best fit involves a model which considers particle-particle interactions. Theories ignoring this interaction predict the moduli of composites of preformed spheroid particles in a rubber matrix. It is thus inferred that there is an interaction between pu and polyvinyl molecules in the interatomic regions.
Having trouble evaluating processability of smc? Here are some handy approaches you can try Okuto, H., Hinano, H. and Yotsuzuka, M. Plastics Technology, Vo119, No 9 (Aug 1973)pp 43-45 Some single in-plant tests requiring no complex equipment have been developed in Japan to evaluate the hardness, flow and cure characteristics of smc to enable the processing parameters to be quickly optimised. The impact strength of fibre composites Williams, T., Allen, G. and Kaufman, M. S. Journal of Materials Science, Vol 8, No 12 (Dec 1973) pp 1765-1787 series of composites of pmma and rubber-toughened pmma reinforced with both long and short fibres, aligned and randomly oriented have been manufactured to verify models developed by the authors to predict crackinitiation energy, notched impact and unnotched impact strengths of fibre-reinforced composites. Good agreement between results and models is obtained and the parameters which appear to control the fracture energy are indicated. Injection mould reinforced thermosets - with fewer headaches Duncan, G. G. Plastics Technology, Vo119, No 9 (Aug 1973) pp 3 5 - 3 7 Guidelines on avoiding problems such as screw wear, gelling in the barrel and bridging in the hopper, when injection moulding fibre-reinforced thermosets, are given. The design of runners and gates to give good fibre separation but minimum degradation is discussed. These aspects of design appear to be at least as important as the action of the screw in determining the mechanical properties of the product. Interfacial fracture energy and the toughness of composites Marston, T. U., Atkins, A. G. and Felbeck, D. K. Journal of Materials Science, Vol 9, No 3 (March 1974) pp 447-455 Since none of the extant theories of toughness successfully predict the work of fracture of the boron/epoxy system, an analysis is proposed here that incorporates the work to create new surfaces and this provides closer agreement with experimental results. This new analysis suggests how to tailor the interracial shear strength in order to obtain a reasonable tough-