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Thermosetting resin composition for injection moulding and article formed by using the composition
Reflection of acoustic waves from water/ composite interfaces Nayfeh, A.H., Crane, R.L. and Hoppe, W.C. Journal of Applied Physics Vo155 No 3 (February 1984) p 685 An approximate analysis for the reflection of an acoustic wave from a water/composite interface is presented. The composite is replaced by a higher order dispersive continuum. A system of coupled field equations describe the dynamic behaviour of the composite. Predictions are compared with experimentally determined values for unidirectional carbon/epoxy and boron/epoxy composites. For the former, the variation in reflection coefficient with frequency is not detectable due to the small difference between fibre diameter and wavelength of the acoustic wave. The a m o u n t of dispersion observed in the boron/epoxy was found to be in satisfactory agreement with theory below 7 MHz. Above this value, where the wavelength approaches the size of the microstructure, deviation from the analysis is shown.
Redisual strength assessment of low velocity impact damage of graphite-epoxy laminates Lal, K.M. Journal of Reinforced Plastics and Composites Vol 2 (October 1983) p 226 An energy dissipation model was developed to predict the residual strength from fracture mechanics concepts. An evaluation of the total energy absorbed was made using the coefficient of restitution concepts, based on sheardominated theory of fibre-reinforced materials. In this study the delamination was also predicted by assuming that the stiffness of the laminate dropped due to debonding. The difference between the total energy and the delamination energy was assumed to be the energy due to fibre breakage and was used to determine the residual strength. It is concluded that better impact-damage resistance would be
at
obtained if composite materials were developed which carried more strain before failure.
density materials tended to show higher activation energies.
A study of acoustic emissions from stressed polypropylene-glass fibre composites
Three dimensional curing stresses in symmetric cross-ply laminates with temperature-dependent properties Hayden Griffin Jr., O. Journal of Composite Materials Vo117 (September 1983) p 449
Belchamber, R.M., Berteridge, D., Chow, Y.T., Hawkes, A.G., Cudby, M.E.A. a n d Wood, D.G.M. Journal of Composite Materials Vol 17 (September 1983) p 420 An experimental investigation into the recognition of different acoustic emissions obtained for a range of materials is presented. Several classes of signal have been identified using r pattern recognition, and a characteristic acoustic emission signal can be obtained for a particular material. The techniques have been used to provide data enabling speculation as to the fracture processes involved. In this way, the presence and the role of the coupling agent in modifying the crack propogation processes which give rise to acoustic emissions have been identified.
Thermal and photo-degradation behaviours of glass-fibre reinforced rigid polyurethane foam Morimoto, K., Suzuki, T. and Yosomiya, R. Journal of Composite Materials Vol 17 (September 1983) p 464 In this study, the thermal and photo-degradation behaviours of glass fibre-reinforced and unreinforced foams have been investigated. Both of these materials exhibited similar degradation behaviour for flexural properties. A weatherometer was used to expose the materials, and samples of higher apparent density (those with short glass fibres) gave rise to a higher reduction in properties. Infrared analysis was shown to reveal a decrease in urethane linkage after weathering. Heat treatment was also carried out and, although no significant difference was observed in activation energy of thermal degradation, in some cases the higher apparent
A fully three-dimensional finite element analysis of curing stresses in cross-ply boron/epoxy composite laminates is presented. Comparisons are made between constant and temperaturedependent material properties and a constitutive model which includes the coupling between stress and temperature dependence of materials properties. Differences in the three thermal expansion models are found to be significant for boron/epoxies in some stress terms and negligible in others. The agreement with the results of previous investigators which included the coupling term is good.
X-ray diffraction studies of carbon fibres in composRes irradiated with 0.5 MeV electrons Kent, M., Wolf, K., Memory, J.D., Fornes, R.E. and Gilbert, ILD. Carbon Vol 22 No 1 (1984) An X-ray diffraction study of two unidirectional carbon fibre composites (T300/epoxy, C6000/ polyimide), irradiated with large doses of 0.5 MeV electrons in 5 Mrad dose increments has been conducted. X-ray diffraction measurements are made at several dose levels up to 8000 Mrads, recording equatorial and meridianal traces. There is no difference in the traces of control samples and those T300/epoxy samples which had received 8000 Mrad doses; a similar result was found for control and irradiated samples of T300 fibres and the C6000/polyimide composite. The conclusion is that this level of radiation does not affect the crystal structure of carbon, which can dissipate or absorb the excitation energy by ionization processes.
tracts oF l Ycents
Abstracts of British Patents are prepared by Dr F.R. Jones, Department of Metallurgy and Materials Technology, University of Surrey, UK
UK PATENTS COMPONENTS Amorphous spherical particles of an inorganic compound for use in dentistry (Tokuyama Soda KK, Japan) GB 2 115 799A (14 September 1983) Filler particles for polymeric matrices (0.1-1.0 ,um in size) are prepared by mixing silicon and metal alkoxides (eg ethyl silicate and sodium methylate, or tetrabutyl titanate) prior to hydrolysis.
Composite material (Westraco Corp, USA) GB 2 116 112 A (21 September 1983) A structural panel of high strength and tough-
244
ness is obtained from, eg unidirectional GRP, by corrugated paper board techniques. The fibres are orientated at + 15° to the corrugation flute in the corrugated material and at -75 ° in the support boards.
Carbon fibre members
reinforced
timber
laminated
(N. Emberson of UK)GB 2 116 907A (5 October 1983) A 'reinforced' wooden beam comprising laminae of wood and carbon fibres is described.
Thermosetting resin composition for injection moulding and article formed by using the composition (Nissan Motor Co Ltd, Japan) GB 2 117 386 A (12 October 1983) A silica-polyphosphate filler for a phenolic or polyester moulding c o m p o u n d is described.
The products have high thermal stability. The filler is considered to promote the cross-linking process in the injection moulder.
Compression moulding vehicle wheels (Motor Wheel Corp, USA) GB 2 117 695/6 A (19 October 1983) A fibre-reinforced composite wheel with a random fibrous disc and a rim with circumferentially aligned fibrous and random laminae is described. The disc charge comprises a stack of precut SMC sheet with different orientations. After moulding the fibres are perpendicular to the wheel axis. The rim charge consists of coiled SMC with fibres oriented randomly and in well defined directions in different laminae to form a double helical array. The whole is compression moulded on a 2-stage mould. Details of the SMC and fatigue performance of the wheel are given.
COMPOSITES . JULY 1984
Redisual strength assessment of low velocity impact damage of graphite-epoxy laminates Lal, K.M. Journal of Reinforced Plastics and Composites Vol 2 (October 1983) p 226 An energy dissipation model was developed to predict the residual strength from fracture mechanics concepts. An evaluation of the total energy absorbed was made using the coefficient of restitution concepts, based on sheardominated theory of fibre-reinforced materials. In this study the delamination was also predicted by assuming that the stiffness of the laminate dropped due to debonding. The difference between the total energy and the delamination energy was assumed to be the energy due to fibre breakage and was used to determine the residual strength. It is concluded that better impact-damage resistance would be
at
obtained if composite materials were developed which carried more strain before failure.
density materials tended to show higher activation energies.
A study of acoustic emissions from stressed polypropylene-glass fibre composites
Three dimensional curing stresses in symmetric cross-ply laminates with temperature-dependent properties Hayden Griffin Jr., O. Journal of Composite Materials Vo117 (September 1983) p 449
Belchamber, R.M., Berteridge, D., Chow, Y.T., Hawkes, A.G., Cudby, M.E.A. a n d Wood, D.G.M. Journal of Composite Materials Vol 17 (September 1983) p 420 An experimental investigation into the recognition of different acoustic emissions obtained for a range of materials is presented. Several classes of signal have been identified using r pattern recognition, and a characteristic acoustic emission signal can be obtained for a particular material. The techniques have been used to provide data enabling speculation as to the fracture processes involved. In this way, the presence and the role of the coupling agent in modifying the crack propogation processes which give rise to acoustic emissions have been identified.
Thermal and photo-degradation behaviours of glass-fibre reinforced rigid polyurethane foam Morimoto, K., Suzuki, T. and Yosomiya, R. Journal of Composite Materials Vol 17 (September 1983) p 464 In this study, the thermal and photo-degradation behaviours of glass fibre-reinforced and unreinforced foams have been investigated. Both of these materials exhibited similar degradation behaviour for flexural properties. A weatherometer was used to expose the materials, and samples of higher apparent density (those with short glass fibres) gave rise to a higher reduction in properties. Infrared analysis was shown to reveal a decrease in urethane linkage after weathering. Heat treatment was also carried out and, although no significant difference was observed in activation energy of thermal degradation, in some cases the higher apparent
A fully three-dimensional finite element analysis of curing stresses in cross-ply boron/epoxy composite laminates is presented. Comparisons are made between constant and temperaturedependent material properties and a constitutive model which includes the coupling between stress and temperature dependence of materials properties. Differences in the three thermal expansion models are found to be significant for boron/epoxies in some stress terms and negligible in others. The agreement with the results of previous investigators which included the coupling term is good.
X-ray diffraction studies of carbon fibres in composRes irradiated with 0.5 MeV electrons Kent, M., Wolf, K., Memory, J.D., Fornes, R.E. and Gilbert, ILD. Carbon Vol 22 No 1 (1984) An X-ray diffraction study of two unidirectional carbon fibre composites (T300/epoxy, C6000/ polyimide), irradiated with large doses of 0.5 MeV electrons in 5 Mrad dose increments has been conducted. X-ray diffraction measurements are made at several dose levels up to 8000 Mrads, recording equatorial and meridianal traces. There is no difference in the traces of control samples and those T300/epoxy samples which had received 8000 Mrad doses; a similar result was found for control and irradiated samples of T300 fibres and the C6000/polyimide composite. The conclusion is that this level of radiation does not affect the crystal structure of carbon, which can dissipate or absorb the excitation energy by ionization processes.
tracts oF l Ycents
Abstracts of British Patents are prepared by Dr F.R. Jones, Department of Metallurgy and Materials Technology, University of Surrey, UK
UK PATENTS COMPONENTS Amorphous spherical particles of an inorganic compound for use in dentistry (Tokuyama Soda KK, Japan) GB 2 115 799A (14 September 1983) Filler particles for polymeric matrices (0.1-1.0 ,um in size) are prepared by mixing silicon and metal alkoxides (eg ethyl silicate and sodium methylate, or tetrabutyl titanate) prior to hydrolysis.
Composite material (Westraco Corp, USA) GB 2 116 112 A (21 September 1983) A structural panel of high strength and tough-
244
ness is obtained from, eg unidirectional GRP, by corrugated paper board techniques. The fibres are orientated at + 15° to the corrugation flute in the corrugated material and at -75 ° in the support boards.
Carbon fibre members
reinforced
timber
laminated
(N. Emberson of UK)GB 2 116 907A (5 October 1983) A 'reinforced' wooden beam comprising laminae of wood and carbon fibres is described.
Thermosetting resin composition for injection moulding and article formed by using the composition (Nissan Motor Co Ltd, Japan) GB 2 117 386 A (12 October 1983) A silica-polyphosphate filler for a phenolic or polyester moulding c o m p o u n d is described.
The products have high thermal stability. The filler is considered to promote the cross-linking process in the injection moulder.
Compression moulding vehicle wheels (Motor Wheel Corp, USA) GB 2 117 695/6 A (19 October 1983) A fibre-reinforced composite wheel with a random fibrous disc and a rim with circumferentially aligned fibrous and random laminae is described. The disc charge comprises a stack of precut SMC sheet with different orientations. After moulding the fibres are perpendicular to the wheel axis. The rim charge consists of coiled SMC with fibres oriented randomly and in well defined directions in different laminae to form a double helical array. The whole is compression moulded on a 2-stage mould. Details of the SMC and fatigue performance of the wheel are given.
COMPOSITES . JULY 1984