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The crystallization and interfacial bond strength of Nylon 6 at carbon and glass fibre surfaces
standpoint of representing widely varying fatigue behaviour.
Molecular correlations with fracture in fibers and granular filled composites DeVries, K.L., Lloyd, B.A. and Wilde, T.B. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 1975) pp 473-489 The results of electron spin resonance studies of chain-scission kinetics in oriented nylon fibres and in granularfilled elastomer composites are presented. Pyrolysis studies on polyacrylonitrile fibres: physical property/chemical structure changes during the initial stages of pyrolysis Ferguson, J. and Mahapatro, B. Fibre Science and Technology, Vol 9, No 3 (July 1976) pp 161-175 The influence of pyrolysis at 220°C in oxygen and nitrogen on the tensile properties of both drawn and undrawn pan fibres was examined. It was found that tensile stress, yield stress and initial modulus exhibit maxima after about 60 minutes pyrolysis in oxygen and 120 minutes in nitrogen. Differential scanning calodmatry indicated that chemical changes were delayed in nitrogen compared with reactions in oxygen. It is suggested that cyclisation and degradation - two competitive reactions - give rise to the results obtained. Reducing variability in composite tensile-strength properties Mills, G.J., Brown, G.G. and Watermann, D.R. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials 1975) pp 352-363 Increases in 'B' design allowable levels for boron and graphite/epoxy material systems are shown to relate to reductions in fibre strength dispersions accompanied by increases in the average values. Projections of composite 'B' allowable to 2.05 GN/m 2 are made for defect-free filaments. On the stress concentration factor in fibrous composites Fukuda, H. and Kawata, K. Fibre Science and Technology, Vol 9, No 3 (July 1976} pp 189-203 Stress states were theoretically determined for a unidirectionaUy reinforced composite material (having some discontinuous fibres) subjected
262
to tensile loading parallel to the fibre direction. Using a previously devised method a stress concentration factor and an ineffective fibre length were calculated. The results were compared with experimental values and results by means of shear-lag theory.
METAL MA TRICES
A computational procedure to analyze metal matrix laminates with non-linear lamination residual strains Chamis, C.C. and Sullivan, T.L. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 19 75) pp 327-339 An approximate computational procedure is described, for the analysis of angle-plied laminates with residual non-linear strains, consisting of a combination of linear composite mechanics and incremental linear laminate theory. The procedure predicted initial tangent properties which were in good agreement with measured data obtained from B/A1 angle-ply laminates. Impact damage effects on boronaluminium composites Carlisle, J.C. etal. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 1975) pp 458-470 The foreign object impact damage associated with jet engines was investigated by impacting both Ti/6A1/4V and B/AI specimens with either steel or room temperature vulcanizing rubber spheres to simulate the two main types of ingested foreign body. The results indicate that a prestressed composite suffers much greater damage than simple cantilevered specimens. A fracture mechanics analysis is presented which successfully predicts the effects of room temperature vulcanizing rubber impact on B[AI composites. Stress-rupture strength and microstructural stability of W-Hf-C wirereinforced superalloy composites Petrasek, D.W. and Siguorelli, R.A. Conference on Composite Reliability, ASTM STP 580 (American Society for Tesring and Materials, 19 75) pp 405424 W-Hf-C/superalloy composites were found to be potentially useful for
turbine blade applications on the basis of stress rupture strength. The 100 and 1000 h rupture strengths obtained for 70 volume % fibre composites tested at 1090°C were 420 and 280 MN/m2. The investigation indicated that with better quality fibres, composites having 100 and 1000 h rupture strengths of 570 and 370 MN/m2 may be obtained. MetaUographic studies indicated sufficient fibre/matrix compatibility for long-time applications at 1090°C for 1000 h or more.
RESIN MA TRICES
The crystallization and interfacial bond strength of Nylon 6 at carbon and glass fibre surfaces Bessell, T. and Shortall, J.B. Journal of Materials Science, Vol I 0 {December 1975)pp 2035-2043 Reinforcing fibres are shown to nucleate a columnar structure in Nylon 6 at the fibre surface, with a marked difference between those structures nucleated by glass and carbon and also between those nucleated by Type I and Type II carbon fibres. The influence of this structure, together with the effect of surface coatings on the fibres, on the interfacial bond strength is discussed. Determination of fracture strength in orthotropic graphite/epoxy laminates Konish, H.J. Jr. and Cruse, T.A. Conference on Composite Reliability, ASTM STP 580 (A merican Society for Testing and Materials, 1975) pp 4905O3 A fracture test programme, performed on orthotropic graphite/epoxy laminates, is reported. The test data are used to evaluate the effects of specimen size and specimen configuration on the measured value of laminate fracture strength. It is shown that the apparent fracture strength is independent of specimen configuration and specimen thickness, but varies signi. ficantly with respect to crack length. Two analytical models for predicting laminate fracture toughness are also evaluated using the test data. It is concluded that linear elastic fracture mechanics does provide a meaningful characterization of crack growth in orthotropic composite laminates, if some specified conditions are met.
COMPOSITES . OCTOBER
1976
Molecular correlations with fracture in fibers and granular filled composites DeVries, K.L., Lloyd, B.A. and Wilde, T.B. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 1975) pp 473-489 The results of electron spin resonance studies of chain-scission kinetics in oriented nylon fibres and in granularfilled elastomer composites are presented. Pyrolysis studies on polyacrylonitrile fibres: physical property/chemical structure changes during the initial stages of pyrolysis Ferguson, J. and Mahapatro, B. Fibre Science and Technology, Vol 9, No 3 (July 1976) pp 161-175 The influence of pyrolysis at 220°C in oxygen and nitrogen on the tensile properties of both drawn and undrawn pan fibres was examined. It was found that tensile stress, yield stress and initial modulus exhibit maxima after about 60 minutes pyrolysis in oxygen and 120 minutes in nitrogen. Differential scanning calodmatry indicated that chemical changes were delayed in nitrogen compared with reactions in oxygen. It is suggested that cyclisation and degradation - two competitive reactions - give rise to the results obtained. Reducing variability in composite tensile-strength properties Mills, G.J., Brown, G.G. and Watermann, D.R. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials 1975) pp 352-363 Increases in 'B' design allowable levels for boron and graphite/epoxy material systems are shown to relate to reductions in fibre strength dispersions accompanied by increases in the average values. Projections of composite 'B' allowable to 2.05 GN/m 2 are made for defect-free filaments. On the stress concentration factor in fibrous composites Fukuda, H. and Kawata, K. Fibre Science and Technology, Vol 9, No 3 (July 1976} pp 189-203 Stress states were theoretically determined for a unidirectionaUy reinforced composite material (having some discontinuous fibres) subjected
262
to tensile loading parallel to the fibre direction. Using a previously devised method a stress concentration factor and an ineffective fibre length were calculated. The results were compared with experimental values and results by means of shear-lag theory.
METAL MA TRICES
A computational procedure to analyze metal matrix laminates with non-linear lamination residual strains Chamis, C.C. and Sullivan, T.L. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 19 75) pp 327-339 An approximate computational procedure is described, for the analysis of angle-plied laminates with residual non-linear strains, consisting of a combination of linear composite mechanics and incremental linear laminate theory. The procedure predicted initial tangent properties which were in good agreement with measured data obtained from B/A1 angle-ply laminates. Impact damage effects on boronaluminium composites Carlisle, J.C. etal. Conference on Composite Reliability, ASTM STP 580 (American Society for Testing and Materials, 1975) pp 458-470 The foreign object impact damage associated with jet engines was investigated by impacting both Ti/6A1/4V and B/AI specimens with either steel or room temperature vulcanizing rubber spheres to simulate the two main types of ingested foreign body. The results indicate that a prestressed composite suffers much greater damage than simple cantilevered specimens. A fracture mechanics analysis is presented which successfully predicts the effects of room temperature vulcanizing rubber impact on B[AI composites. Stress-rupture strength and microstructural stability of W-Hf-C wirereinforced superalloy composites Petrasek, D.W. and Siguorelli, R.A. Conference on Composite Reliability, ASTM STP 580 (American Society for Tesring and Materials, 19 75) pp 405424 W-Hf-C/superalloy composites were found to be potentially useful for
turbine blade applications on the basis of stress rupture strength. The 100 and 1000 h rupture strengths obtained for 70 volume % fibre composites tested at 1090°C were 420 and 280 MN/m2. The investigation indicated that with better quality fibres, composites having 100 and 1000 h rupture strengths of 570 and 370 MN/m2 may be obtained. MetaUographic studies indicated sufficient fibre/matrix compatibility for long-time applications at 1090°C for 1000 h or more.
RESIN MA TRICES
The crystallization and interfacial bond strength of Nylon 6 at carbon and glass fibre surfaces Bessell, T. and Shortall, J.B. Journal of Materials Science, Vol I 0 {December 1975)pp 2035-2043 Reinforcing fibres are shown to nucleate a columnar structure in Nylon 6 at the fibre surface, with a marked difference between those structures nucleated by glass and carbon and also between those nucleated by Type I and Type II carbon fibres. The influence of this structure, together with the effect of surface coatings on the fibres, on the interfacial bond strength is discussed. Determination of fracture strength in orthotropic graphite/epoxy laminates Konish, H.J. Jr. and Cruse, T.A. Conference on Composite Reliability, ASTM STP 580 (A merican Society for Testing and Materials, 1975) pp 4905O3 A fracture test programme, performed on orthotropic graphite/epoxy laminates, is reported. The test data are used to evaluate the effects of specimen size and specimen configuration on the measured value of laminate fracture strength. It is shown that the apparent fracture strength is independent of specimen configuration and specimen thickness, but varies signi. ficantly with respect to crack length. Two analytical models for predicting laminate fracture toughness are also evaluated using the test data. It is concluded that linear elastic fracture mechanics does provide a meaningful characterization of crack growth in orthotropic composite laminates, if some specified conditions are met.
COMPOSITES . OCTOBER
1976