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Hygrothermal ageing and fracture of glass fibre-epoxy composites
anisms by which the interphase affects fibre/ matrix interfacial shear strength is given.
Controlled interracial bonding on the strength and fracture toughness of Kevlar and carbon fibre composites Mai, Y.W. Journal of Materials Science Letters Vol 2 (1983) p 723 Improved fracture toughness in composites may be obtained by controlling the bonding of the fibres and the matrix resin. In this study, Kcvlar and carbon fibres were coated with either Dow Coming SV200--a silicon vacuum fluid--or a blend of polyester and polycther resins, these were Part A of a two-pack polyurethane compound Estapol 7008. Fracture toughness was measured using a threepoint bend test. Little improvement was observed in the Kevlar or carbon composites fabricated using the silicone-treated fibres. Improvement of up to 200% was found for Kevlar treated with Estapol 7008, and of about 50% for similarly treated carbon. Hygrothermal ageing reduces these values, however, the Kevlar composites were still better than those fabricated from untreated fibres.
Dynamic mechanical analysis of epoxy composite prepregs Lauer, L.D. SAMPE Quarterly 1Iol 15 Vol 1 (October 1983) pp 31-35 A new method of dynamic mechanical analysis of epoxy prepregs using a rheometrics dynamic spectrometer with a parallel plate fixture in the tension-compression mode is described.
The effect of ioterfuciai adhesion on the mechanism for craze formation in polystyrene-glass bead composites Dekkers, M.E.J. and Heikens, D. Journal of Materials Science Vo116 No II p 3281 Silane treatments were used to obtain a range of composites of different interfacial bond strengths. These were tested in uniaxial tension, and isolated glass beads were subjected to finite element analysis. Evidence is proposed which suggests that there is a different craze formation mechanism in composites with a strong interfacial bond strength than in those with a weak bond. Those beads bonded with strong interfaces endure crazes at the bead poles in the region of maximum dilation and maximum principal stress. The weaker bonded beads form crazes at the interface between the pole and the equator, and it is thought that this process is preceded by dewetting along the phase boundaries.
Effects of water on #ass-filled methacrylate resins Sbdcrholm, K.J. and Calvert, P.D. Journal of Materials Science Vo118 No 10 p 2957 Two types of methacrylate resins were reinforced with up to 50% volume fraction of glass beads. The two resins were poly (methylmethacrylate) and a cross-linked triethylcneglycoldimethacrylate. On immersion in water at 60°C the composites were monitored for weight change, elastic modulus and compressive strength. After five days immersion, the water uptake levelled off and the modulus and strengths were suitably reduced due to matrix plasticization. The polymethylmethyacrylate, however, was
164
observed to increase in modulus and strength thereafter, while the cross-linked matrix composites remained plasticized. Silane treatments were used on the glass beads and resulted in reduced water uptake and the retention of higher strength and modulus.
Engineering today's plastics for tomorrow's applications Wahrenberg II, R.H. Materials Engineering (August 1983) p 25 The current advances in the American plastics industry is reviewed. New materials, chiefly composites, are finding new applications in many fields considered revolutionary for conventional polymers. In this article, glassreinforced polyphenylencsulphide, polyfunctional epoxy resins (aimed at the aircraft CFRP market), flame retardant alumina trihydrate/ polypropenc composites, new nylons and their composites, glass fibre-reinforced polybutylcne tcrephthalatc foam, magnesium oxysulphate fibre-reinforced polypropylcne, and phenolic fibre reinforcement are all discussed, and their likely applications proposed.
Flight service of composite structure on McDonnel Douglas commercial airplanes Kom, C.Y. and Gaidulis, J. SAMPE Quarterly Vol 15 No 1 (October 1983) pp 36-44 The developments that led to the introduction of advanced composite materials in commercial aircraft from the Douglas Aircraft Company are reviewed. Emphasis is given to carbon/ epoxy structural components on the Super 80 and DC-10. Future plans for the development and production of advanced composite structures are also given.
Fracture of random short-fibre SMC composite Wang S.S., Chim, E.S.-M., Yu, T.P. and Goetz, D.P. Journal of Composite Materials Vol 17 No 4 (July 1983) pp 299-315 The fracture behaviour of a randomly oriented, short-glass fibre-reinforced SMC composite has been studied. Experiments conducted on notched SMC-RS0 composite plates were used to determine the fracture toughness under Mode-I and Mode-II loading K IQ and K llQFracture tests on the same composite under mixed-mode loading suggest thatK I andK II at fracture follow the relation (K I/K /C) + (K 11/ K IIQ)2 = 1. The applicability of the WhitneyNuismer two-parameter model for determining strength properties of a notched composite was found to be questionable.
Hot alkali stable materials with low electrical resistance: a new composite made from porous asbestos and soluble polyphenylene sulphide Montoneri, E., Giuffrt, L., Modica, G. and Gennuso, M. Journal of Materials Science Vo118 No 11 p 3311 This new composite has been developed through the innovation of dissolving polyphenylsulphide (PPS) at high concentrations in diphenylsulphide, and subsequently coating asbestos cardboard. The physisorbcd organic polymer stabilizes the asbestos mat, and the resultant composite properties may be dictated by controlling the proportion of polymer present. Increases in mechanical strength, chemical stability (up to 43% KOH) and low electrical resistance are obtained by this new composite
which, it is suggested, are properties required in alkaline water electrolysers. A discussion of the mechanisms of stabilizing the asbestos by the PPS along with the physical chemical and mechanical properties is made.
Hygrothermal ageing and fracture of glass fibreepoxy composites Anstice, P.D. and Beaumont, P.W.R. Journal of Materials Science Vo118 No 11 p 3404 A collection of data based on the direct observation and measurement of fibre dcbond length and fibre pull-out length after fracture is displayed in empirical failure diagrams. Work of fracture measurements are displayed in a three-dimensional plot against humidity and ageing time. This information is combined with fracture models by the construction of a fracture map which has been used to interpret hygrothermal ageing
Optimising properties of glass reinforced phenolics by postcuring Daniels, D.A. and FIRS, B.B. Materials Engineerineering (August 1983) p 14 A study is made into the postcuring of glassreinforced phenolics. A one-step moulding compound is compared with two two-step moulding compounds of different glass fibre volume fractions. The advantages in postcuring are highlighted (ie completion of cure, removal of volatiles, stress relief, higher tolerances especially at elevated temperatures), weight losses are discussed and postcuring recommendations are made. The effect of the postcuring technique is illustrated on a range of mechanical properties using the described moulding compounds.
Rain erosion mechanisms on polyurethane and fluoroelastomer coated composite constructions Hurley, C.J. ZahavL J. and SchmitL G.F. SAMPE Quarterly Iiol 15 No 1 (October 1983) pp 16-30 Rain erosion impact resistance of polyurethane and fluoroelastomer coatings on glass/epoxy, graphite/epoxy and quartz/polyimide composite constructions were investigated at 90°C and 30°C impact angles. Cratering initiation and crack propagation processes were observed using scanning electron microscopy techniques.
Statistical analysis of multiple fracture in 0°190°/ 0 ° glass fibre/epoxy resin laminates Manders, P.W., Chou, T.W., Jones, F.R. and Rock, J.W. Journal of Materials Science Iiol 18 No 10 p 2876 Observations of the transverse cracking spacings in 00/900/0 ° glass fibre/epoxy laminates showed a strength variability. A model incorporating a Weibull distribution of strength is shown to be a good description of the crack spacings. The variability of strength is reported to give rise to a size effect in which the first crack appears at a strain which increases as the length of the specimen is decreased. A "stress whitening" phenomenon is observed as a result of stress magnification in the matrix, which is proposed as a fibre/matrix debonding event. This is a reversible debond, and it is noted as being indicative of the approximate distributions of stress in the 90° ply.
COMPOSITES. APRIL 1984
Controlled interracial bonding on the strength and fracture toughness of Kevlar and carbon fibre composites Mai, Y.W. Journal of Materials Science Letters Vol 2 (1983) p 723 Improved fracture toughness in composites may be obtained by controlling the bonding of the fibres and the matrix resin. In this study, Kcvlar and carbon fibres were coated with either Dow Coming SV200--a silicon vacuum fluid--or a blend of polyester and polycther resins, these were Part A of a two-pack polyurethane compound Estapol 7008. Fracture toughness was measured using a threepoint bend test. Little improvement was observed in the Kevlar or carbon composites fabricated using the silicone-treated fibres. Improvement of up to 200% was found for Kevlar treated with Estapol 7008, and of about 50% for similarly treated carbon. Hygrothermal ageing reduces these values, however, the Kevlar composites were still better than those fabricated from untreated fibres.
Dynamic mechanical analysis of epoxy composite prepregs Lauer, L.D. SAMPE Quarterly 1Iol 15 Vol 1 (October 1983) pp 31-35 A new method of dynamic mechanical analysis of epoxy prepregs using a rheometrics dynamic spectrometer with a parallel plate fixture in the tension-compression mode is described.
The effect of ioterfuciai adhesion on the mechanism for craze formation in polystyrene-glass bead composites Dekkers, M.E.J. and Heikens, D. Journal of Materials Science Vo116 No II p 3281 Silane treatments were used to obtain a range of composites of different interfacial bond strengths. These were tested in uniaxial tension, and isolated glass beads were subjected to finite element analysis. Evidence is proposed which suggests that there is a different craze formation mechanism in composites with a strong interfacial bond strength than in those with a weak bond. Those beads bonded with strong interfaces endure crazes at the bead poles in the region of maximum dilation and maximum principal stress. The weaker bonded beads form crazes at the interface between the pole and the equator, and it is thought that this process is preceded by dewetting along the phase boundaries.
Effects of water on #ass-filled methacrylate resins Sbdcrholm, K.J. and Calvert, P.D. Journal of Materials Science Vo118 No 10 p 2957 Two types of methacrylate resins were reinforced with up to 50% volume fraction of glass beads. The two resins were poly (methylmethacrylate) and a cross-linked triethylcneglycoldimethacrylate. On immersion in water at 60°C the composites were monitored for weight change, elastic modulus and compressive strength. After five days immersion, the water uptake levelled off and the modulus and strengths were suitably reduced due to matrix plasticization. The polymethylmethyacrylate, however, was
164
observed to increase in modulus and strength thereafter, while the cross-linked matrix composites remained plasticized. Silane treatments were used on the glass beads and resulted in reduced water uptake and the retention of higher strength and modulus.
Engineering today's plastics for tomorrow's applications Wahrenberg II, R.H. Materials Engineering (August 1983) p 25 The current advances in the American plastics industry is reviewed. New materials, chiefly composites, are finding new applications in many fields considered revolutionary for conventional polymers. In this article, glassreinforced polyphenylencsulphide, polyfunctional epoxy resins (aimed at the aircraft CFRP market), flame retardant alumina trihydrate/ polypropenc composites, new nylons and their composites, glass fibre-reinforced polybutylcne tcrephthalatc foam, magnesium oxysulphate fibre-reinforced polypropylcne, and phenolic fibre reinforcement are all discussed, and their likely applications proposed.
Flight service of composite structure on McDonnel Douglas commercial airplanes Kom, C.Y. and Gaidulis, J. SAMPE Quarterly Vol 15 No 1 (October 1983) pp 36-44 The developments that led to the introduction of advanced composite materials in commercial aircraft from the Douglas Aircraft Company are reviewed. Emphasis is given to carbon/ epoxy structural components on the Super 80 and DC-10. Future plans for the development and production of advanced composite structures are also given.
Fracture of random short-fibre SMC composite Wang S.S., Chim, E.S.-M., Yu, T.P. and Goetz, D.P. Journal of Composite Materials Vol 17 No 4 (July 1983) pp 299-315 The fracture behaviour of a randomly oriented, short-glass fibre-reinforced SMC composite has been studied. Experiments conducted on notched SMC-RS0 composite plates were used to determine the fracture toughness under Mode-I and Mode-II loading K IQ and K llQFracture tests on the same composite under mixed-mode loading suggest thatK I andK II at fracture follow the relation (K I/K /C) + (K 11/ K IIQ)2 = 1. The applicability of the WhitneyNuismer two-parameter model for determining strength properties of a notched composite was found to be questionable.
Hot alkali stable materials with low electrical resistance: a new composite made from porous asbestos and soluble polyphenylene sulphide Montoneri, E., Giuffrt, L., Modica, G. and Gennuso, M. Journal of Materials Science Vo118 No 11 p 3311 This new composite has been developed through the innovation of dissolving polyphenylsulphide (PPS) at high concentrations in diphenylsulphide, and subsequently coating asbestos cardboard. The physisorbcd organic polymer stabilizes the asbestos mat, and the resultant composite properties may be dictated by controlling the proportion of polymer present. Increases in mechanical strength, chemical stability (up to 43% KOH) and low electrical resistance are obtained by this new composite
which, it is suggested, are properties required in alkaline water electrolysers. A discussion of the mechanisms of stabilizing the asbestos by the PPS along with the physical chemical and mechanical properties is made.
Hygrothermal ageing and fracture of glass fibreepoxy composites Anstice, P.D. and Beaumont, P.W.R. Journal of Materials Science Vo118 No 11 p 3404 A collection of data based on the direct observation and measurement of fibre dcbond length and fibre pull-out length after fracture is displayed in empirical failure diagrams. Work of fracture measurements are displayed in a three-dimensional plot against humidity and ageing time. This information is combined with fracture models by the construction of a fracture map which has been used to interpret hygrothermal ageing
Optimising properties of glass reinforced phenolics by postcuring Daniels, D.A. and FIRS, B.B. Materials Engineerineering (August 1983) p 14 A study is made into the postcuring of glassreinforced phenolics. A one-step moulding compound is compared with two two-step moulding compounds of different glass fibre volume fractions. The advantages in postcuring are highlighted (ie completion of cure, removal of volatiles, stress relief, higher tolerances especially at elevated temperatures), weight losses are discussed and postcuring recommendations are made. The effect of the postcuring technique is illustrated on a range of mechanical properties using the described moulding compounds.
Rain erosion mechanisms on polyurethane and fluoroelastomer coated composite constructions Hurley, C.J. ZahavL J. and SchmitL G.F. SAMPE Quarterly Iiol 15 No 1 (October 1983) pp 16-30 Rain erosion impact resistance of polyurethane and fluoroelastomer coatings on glass/epoxy, graphite/epoxy and quartz/polyimide composite constructions were investigated at 90°C and 30°C impact angles. Cratering initiation and crack propagation processes were observed using scanning electron microscopy techniques.
Statistical analysis of multiple fracture in 0°190°/ 0 ° glass fibre/epoxy resin laminates Manders, P.W., Chou, T.W., Jones, F.R. and Rock, J.W. Journal of Materials Science Iiol 18 No 10 p 2876 Observations of the transverse cracking spacings in 00/900/0 ° glass fibre/epoxy laminates showed a strength variability. A model incorporating a Weibull distribution of strength is shown to be a good description of the crack spacings. The variability of strength is reported to give rise to a size effect in which the first crack appears at a strain which increases as the length of the specimen is decreased. A "stress whitening" phenomenon is observed as a result of stress magnification in the matrix, which is proposed as a fibre/matrix debonding event. This is a reversible debond, and it is noted as being indicative of the approximate distributions of stress in the 90° ply.
COMPOSITES. APRIL 1984