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Heat-treatable cladding for new aluminium alloy 7050-T76 sheet
Abstracts of journals Compiled by H. A. Barker, I. Bell, B. Gill and 7". Feest. Abstracts are arranged, in the relevant sections, in alphabetical order of titles (ignoring definite and indefinite articles).
CARBON MA TRICES Mechanical tests of a threedimensionally reinforced carboncarbon composite material Perry, J.L. and Adams, D.F. Carbon Vo114 No 1 (1976) pp 61-70 A tightly woven block consisting of high modulus graphite fibre yarns in a three dimensional array was repeatedly impregnated with a series of low viscosity polymer resins, each reimpregnation being followed by a 1540°C carbonization process. After
The effect of concentration on the wetting and bonding behaviour between nickel alloys and AL23 alumina or sapphire substrates has been investigated. The addition of 1 wt% chromium or 0.1 wt% yttrium produces a decrease in contact angles at 1570°C but not sufficient to cause wetting. Additions of up to 1 or 2 wt% chromium or 0.02 or 0.08 wt% yttrium improves the bonding but further additions cause weakening,
thirteen such re-impregnations, the densified block was graphitized at 2650°C. Strength and modulus were measured after the seventh and thirteenth carbonizations and after graphitization. These properties are compared with photo micrographs of cross-sections of the block taken at various process stages. The influence of the unisotropic thermal expansion characteristics of the composite on the variations in mechanical properties is discussed,
GENERAL
Thermophysical properties of carbon• graphite fibres and MOD-3 fibrereinforced graphite Lee, H.J. and Taylor, R.E. Carbon Vo113 No 6 (1975) pp 521-527 The flash method is extended to measure directly the thermal diffusivity of graphite/carbon fibre in unidirectionally fibre-reinforced composites and also in fibre bundles. In addition thermal conductivity of composite samples measured by an absolute method. The thermal diffusivity of MOD-3 fibre-reinforced graphite was measured and the results used to compute the thermal conductivity in the three orthogonal directions.
CERAMIC MA TRICES The wetting and bonding behaviour of some nickel alloy-alumina systems Crispin, R.M. and Nicholas, M. Journal of Materials Science Vo111 (January 1976)pp 17-21
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Bounds for effective permittivities of Lossy Dielectric composites Schulgasser, K. and Hashin, Z. Journal of Applied Physics Vo147 (February1976) pp 424-428 A homogeneous and isotropic two phase composite is considered, the constituents of which are dielectric with low loss factors. Utilising the fact that the imaginary part of the complex permittivity is low compared to the real part it is possible to derive bounds for the dielectric behaviour. The bounds on the loss factor are found to be the best possible based only on volume fractions and constituent properties. Also, for dielectric constituents whose constants do not vary with frequency the loss factor of the composites is a simple linear combination of the loss factors of the constituents, Dynamic mechanical properties of carbon fibres Voct, A., Morawski, J-C, and Donnet, J-B. Carbon Vo113 No 6 1975 pp 465-468 The dynamic mechanical properties of carbon and graphite fibres at different temperatures have been determined in a low frequency range (0.01-10 Hz) and the influence of fibre stretching evaluated. The results, showing frequency and extension dependent losses and changes in Young's moduli, indicate the presence of relatively large, independently
mobile fibre constituents, which appear to correspond to the slowly undulating ribbons recognized earlier as the basic carbon fibre components. Fatigue behaviour of composite laminate Hahn, H.T. and Kim, R.Y. Journal of Composite Materials Vo110 (April 19 76)pp 156-180 The characterization of fatigue behaviour of glass/epoxy laminate in terms of a variety of parameters is described. The primary failure process responsible up to about 106 cycles of fatigue life is wear-out followed by chance failure. Change of secant modulus can be used as a measure of the extent of damage. Preloading to a high stress level has negligible effect on the residual tensile strength if the fatigue stress is low. However, ply failure and partial delamination result in a moderate loss of compression buckling strength. Fatigue crack propagation rates in woven and non-woven fiber glass laminates Mandell, J.F. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials,1975) pp 515-527 The characteristics of fatigue crack propagation are described for glass fibre laminates containing woven fabric, woven roving, chopped fibre mat and unidirectional ply reinforcement. The crack propagation mode is shown to be a stepwise, ligamentby-ligament advance of the crack front. The rate of crack propagation is predicted by theory, and this theory is found to agree well with experimental observations. Heat-treatable cladding for new aluminium alloy 7050-T76 sheet Staley, J.T. Conference on Composite Reliability, ASTMSTP580 (American Society for testing and materials, 1975) pp 621-632 Four alloys were evaluated as candidates for a cladding on alurninium alloy
COMPOSITES. JANUARY 1977
7050-T76 sheet. It was found that composites of the alloy clad with alloys containing higher amounts of Zn (6.5%) and magnesium (1.8%) developed comparable static mechanical properties and greater fatigue strengths, but were susceptible to stress-corrosion cracking of the cladding and were, consequently, unacceptable.
Interlaminar stresses of uniformly loaded rectangular composite plates Tang, S. Journal of Composite
Materials Vo110 (January 1976) pp 69-78 An analytical solution is obtained for bending a rectangular composite plate with two sides simply-supported and the other two sides free. The interlaminar shear stresses and the normal or 'peel' stress near and at the free edges of the plate are predicted. This would play a dominant role in fatigue fracture of composite plates such as automobile leaf-springs and many orthopaedic implant devices.
Ion exchange strengthening of glass used in the manufacturing of glass fibre Evstishenkon, U.S., Kuznetson, A.I. and Basalaeva, T.S. Glass and Ceramics Vo132 (January 1976) pp 335-337 Studies have been made of the feasibility of increasing the strength of glass using low temperature ion exchange. The glass used was that normally used in production of glass fibre; SiO2,77%; Na=O, 20%; A12Oa, 3%. The glass was treated in a KNOa melt, sometimes containing AgNOa additions. Considerable strength improvements were obtained and the silver nitrate was observed to be beneficial. The improvement is attributed to a compressively stressed layer at the surface,
Moisture absorption and desorption of composite materials Shen, C.-H, and Springer, G.S. Journal of Composite Materials, Vo110 (January 1976) pp 2-20 Expressions are presented for the moisture distribution and the moisture content as a function of time of one dimensional homogeneous and composite materials exposed to humid air or water. Test procedures are described for determining experimentally the values of the moisture content and
COMPOSITES. JANUARY 1977
the diffusivity of composite materials. Extension of the results to materials, exposed to time varying environmental conditions is indicated
Hastic flow rule of laminated eomposites Pei, C.C. and Chou, D.K. Journal of
Composite Materials Vol 10 (January 1976) pp 55-68 Under certain operating conditions, composite materials may exhibit plastic flow properties, instead of the more common elastic deformation and brittle failure. Composite turbine blades operating under high temperature, composite armour subjected to high pressure impact and epoxy matrix that becomes plasticized by moisture absorption are examples where plastic flow may occur. In this paper a plastic flow rule is derived for laminated media.
Thermal conductivity of highmodulus carbon fibers Kalnin, I.L. Conference on
Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 19 75)pp 560-573 The axial thermal conductivity of high modulus carbon fibres near room temperature was determined from the measured thermal conductivity of their unidirectional composites and also directly on a dry fibre bundle. The thermal conductivity of 14 commercial carbon fibre grades ranged from 1.42 W/cm°C to 0.03 for highest and lowest modulus fibres respectively. Correlations are given for thermal and electrical conductivities.
Thermal warping of layered composites Chow, T.S. Journal of Applied
Physics Vo147 (April 1976} pp 1351-1355 The effect of shear deformation on a Properties of filamentary-reinforced layered composite being heated to a composites at cryogenic temperatures prescribed temperature is analysed Kasen, M.B. Conference on Composite according to a recently developed Reliability ASTM STP 580 (American theory for assymetric laminated plates. Society for Testing and Materials, Expanding the fundamental solution 1975) pp 586-611 of thermal stress and converting into This paper presents a review of a series a power series form, the first approxiof significant publications on the mation gives Timoshenko's plate mechanical and thermal properties of equation. In addition to Timoshenko's filamentary-reinforced structural shear correction factor, a thermal shear composites in the cryogenic temperacorrection parameter has to be introture range. The objective, scope of work, duced for thermal expansion problems. and significant conclusions of the selected works are discussed. The temperature dependence of the ultimate Crack initiation in B-AI composites tensile strength, tensile modulus, Hoover, W.R. Journal of Composite thermal conductivity, and thermal MaterialsVol 10 (April 1976) pp 106contraction (expansion) is presented 117 for selected composites developed in The toughness of notched unidireceach programme. Problem areas are tional B-A1 composites under threedef'med and suggestions are made for point bending has been examined as future work. a function of filament volume fraction, filament diameter and matrix yield strength. The results illustrate The stochastic finite element simulathe work of fracture criterion for tion of parallel fibre composites toughness has only limited utility Larder, R.A. and Beadle, C.W. since it was found to be a strong Journal of Composite Materials function of notch length. The linear Vo110 (January 1976) pp 21-31 elastic fracture toughness, Kc, was A method is presented of simulating influenced by changes in the matrix the randomly occurring damage in a yield strength. The critical energy parallel fibre composite subject to release rate, Lc, was shown to be static loading. Stress concentration independent of crack length, filament effects introduced by fibre failure diameter and matrix yield strength are considered and force/deflection and it has been proposed that this curves obtained. Failure stress of the criterion is thus a measure of the entire model can be estimated by parameter which controls composite observing the number of fibre failures crack initiation/strain in the filaments per load increment, at the notch root.
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CARBON MA TRICES Mechanical tests of a threedimensionally reinforced carboncarbon composite material Perry, J.L. and Adams, D.F. Carbon Vo114 No 1 (1976) pp 61-70 A tightly woven block consisting of high modulus graphite fibre yarns in a three dimensional array was repeatedly impregnated with a series of low viscosity polymer resins, each reimpregnation being followed by a 1540°C carbonization process. After
The effect of concentration on the wetting and bonding behaviour between nickel alloys and AL23 alumina or sapphire substrates has been investigated. The addition of 1 wt% chromium or 0.1 wt% yttrium produces a decrease in contact angles at 1570°C but not sufficient to cause wetting. Additions of up to 1 or 2 wt% chromium or 0.02 or 0.08 wt% yttrium improves the bonding but further additions cause weakening,
thirteen such re-impregnations, the densified block was graphitized at 2650°C. Strength and modulus were measured after the seventh and thirteenth carbonizations and after graphitization. These properties are compared with photo micrographs of cross-sections of the block taken at various process stages. The influence of the unisotropic thermal expansion characteristics of the composite on the variations in mechanical properties is discussed,
GENERAL
Thermophysical properties of carbon• graphite fibres and MOD-3 fibrereinforced graphite Lee, H.J. and Taylor, R.E. Carbon Vo113 No 6 (1975) pp 521-527 The flash method is extended to measure directly the thermal diffusivity of graphite/carbon fibre in unidirectionally fibre-reinforced composites and also in fibre bundles. In addition thermal conductivity of composite samples measured by an absolute method. The thermal diffusivity of MOD-3 fibre-reinforced graphite was measured and the results used to compute the thermal conductivity in the three orthogonal directions.
CERAMIC MA TRICES The wetting and bonding behaviour of some nickel alloy-alumina systems Crispin, R.M. and Nicholas, M. Journal of Materials Science Vo111 (January 1976)pp 17-21
62
Bounds for effective permittivities of Lossy Dielectric composites Schulgasser, K. and Hashin, Z. Journal of Applied Physics Vo147 (February1976) pp 424-428 A homogeneous and isotropic two phase composite is considered, the constituents of which are dielectric with low loss factors. Utilising the fact that the imaginary part of the complex permittivity is low compared to the real part it is possible to derive bounds for the dielectric behaviour. The bounds on the loss factor are found to be the best possible based only on volume fractions and constituent properties. Also, for dielectric constituents whose constants do not vary with frequency the loss factor of the composites is a simple linear combination of the loss factors of the constituents, Dynamic mechanical properties of carbon fibres Voct, A., Morawski, J-C, and Donnet, J-B. Carbon Vo113 No 6 1975 pp 465-468 The dynamic mechanical properties of carbon and graphite fibres at different temperatures have been determined in a low frequency range (0.01-10 Hz) and the influence of fibre stretching evaluated. The results, showing frequency and extension dependent losses and changes in Young's moduli, indicate the presence of relatively large, independently
mobile fibre constituents, which appear to correspond to the slowly undulating ribbons recognized earlier as the basic carbon fibre components. Fatigue behaviour of composite laminate Hahn, H.T. and Kim, R.Y. Journal of Composite Materials Vo110 (April 19 76)pp 156-180 The characterization of fatigue behaviour of glass/epoxy laminate in terms of a variety of parameters is described. The primary failure process responsible up to about 106 cycles of fatigue life is wear-out followed by chance failure. Change of secant modulus can be used as a measure of the extent of damage. Preloading to a high stress level has negligible effect on the residual tensile strength if the fatigue stress is low. However, ply failure and partial delamination result in a moderate loss of compression buckling strength. Fatigue crack propagation rates in woven and non-woven fiber glass laminates Mandell, J.F. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials,1975) pp 515-527 The characteristics of fatigue crack propagation are described for glass fibre laminates containing woven fabric, woven roving, chopped fibre mat and unidirectional ply reinforcement. The crack propagation mode is shown to be a stepwise, ligamentby-ligament advance of the crack front. The rate of crack propagation is predicted by theory, and this theory is found to agree well with experimental observations. Heat-treatable cladding for new aluminium alloy 7050-T76 sheet Staley, J.T. Conference on Composite Reliability, ASTMSTP580 (American Society for testing and materials, 1975) pp 621-632 Four alloys were evaluated as candidates for a cladding on alurninium alloy
COMPOSITES. JANUARY 1977
7050-T76 sheet. It was found that composites of the alloy clad with alloys containing higher amounts of Zn (6.5%) and magnesium (1.8%) developed comparable static mechanical properties and greater fatigue strengths, but were susceptible to stress-corrosion cracking of the cladding and were, consequently, unacceptable.
Interlaminar stresses of uniformly loaded rectangular composite plates Tang, S. Journal of Composite
Materials Vo110 (January 1976) pp 69-78 An analytical solution is obtained for bending a rectangular composite plate with two sides simply-supported and the other two sides free. The interlaminar shear stresses and the normal or 'peel' stress near and at the free edges of the plate are predicted. This would play a dominant role in fatigue fracture of composite plates such as automobile leaf-springs and many orthopaedic implant devices.
Ion exchange strengthening of glass used in the manufacturing of glass fibre Evstishenkon, U.S., Kuznetson, A.I. and Basalaeva, T.S. Glass and Ceramics Vo132 (January 1976) pp 335-337 Studies have been made of the feasibility of increasing the strength of glass using low temperature ion exchange. The glass used was that normally used in production of glass fibre; SiO2,77%; Na=O, 20%; A12Oa, 3%. The glass was treated in a KNOa melt, sometimes containing AgNOa additions. Considerable strength improvements were obtained and the silver nitrate was observed to be beneficial. The improvement is attributed to a compressively stressed layer at the surface,
Moisture absorption and desorption of composite materials Shen, C.-H, and Springer, G.S. Journal of Composite Materials, Vo110 (January 1976) pp 2-20 Expressions are presented for the moisture distribution and the moisture content as a function of time of one dimensional homogeneous and composite materials exposed to humid air or water. Test procedures are described for determining experimentally the values of the moisture content and
COMPOSITES. JANUARY 1977
the diffusivity of composite materials. Extension of the results to materials, exposed to time varying environmental conditions is indicated
Hastic flow rule of laminated eomposites Pei, C.C. and Chou, D.K. Journal of
Composite Materials Vol 10 (January 1976) pp 55-68 Under certain operating conditions, composite materials may exhibit plastic flow properties, instead of the more common elastic deformation and brittle failure. Composite turbine blades operating under high temperature, composite armour subjected to high pressure impact and epoxy matrix that becomes plasticized by moisture absorption are examples where plastic flow may occur. In this paper a plastic flow rule is derived for laminated media.
Thermal conductivity of highmodulus carbon fibers Kalnin, I.L. Conference on
Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 19 75)pp 560-573 The axial thermal conductivity of high modulus carbon fibres near room temperature was determined from the measured thermal conductivity of their unidirectional composites and also directly on a dry fibre bundle. The thermal conductivity of 14 commercial carbon fibre grades ranged from 1.42 W/cm°C to 0.03 for highest and lowest modulus fibres respectively. Correlations are given for thermal and electrical conductivities.
Thermal warping of layered composites Chow, T.S. Journal of Applied
Physics Vo147 (April 1976} pp 1351-1355 The effect of shear deformation on a Properties of filamentary-reinforced layered composite being heated to a composites at cryogenic temperatures prescribed temperature is analysed Kasen, M.B. Conference on Composite according to a recently developed Reliability ASTM STP 580 (American theory for assymetric laminated plates. Society for Testing and Materials, Expanding the fundamental solution 1975) pp 586-611 of thermal stress and converting into This paper presents a review of a series a power series form, the first approxiof significant publications on the mation gives Timoshenko's plate mechanical and thermal properties of equation. In addition to Timoshenko's filamentary-reinforced structural shear correction factor, a thermal shear composites in the cryogenic temperacorrection parameter has to be introture range. The objective, scope of work, duced for thermal expansion problems. and significant conclusions of the selected works are discussed. The temperature dependence of the ultimate Crack initiation in B-AI composites tensile strength, tensile modulus, Hoover, W.R. Journal of Composite thermal conductivity, and thermal MaterialsVol 10 (April 1976) pp 106contraction (expansion) is presented 117 for selected composites developed in The toughness of notched unidireceach programme. Problem areas are tional B-A1 composites under threedef'med and suggestions are made for point bending has been examined as future work. a function of filament volume fraction, filament diameter and matrix yield strength. The results illustrate The stochastic finite element simulathe work of fracture criterion for tion of parallel fibre composites toughness has only limited utility Larder, R.A. and Beadle, C.W. since it was found to be a strong Journal of Composite Materials function of notch length. The linear Vo110 (January 1976) pp 21-31 elastic fracture toughness, Kc, was A method is presented of simulating influenced by changes in the matrix the randomly occurring damage in a yield strength. The critical energy parallel fibre composite subject to release rate, Lc, was shown to be static loading. Stress concentration independent of crack length, filament effects introduced by fibre failure diameter and matrix yield strength are considered and force/deflection and it has been proposed that this curves obtained. Failure stress of the criterion is thus a measure of the entire model can be estimated by parameter which controls composite observing the number of fibre failures crack initiation/strain in the filaments per load increment, at the notch root.
63