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Composite materials: mechanics, mechanical properties and fabrication
BoOk reviews Processing and uses of carbon fibre reinforced plastics Translated by: M. S. Welling
VDI- Verlag GmbH, Dusseldorf (1981) DM 122 This slim volume (282 pp) contains 15 papers which were apparently presented at the second VDI conference on carbon fibre-reinforced plastics, although this is not stated. The authors are drawn from a number of West German, Austrian and Swiss organizations with the exception of one from the USA. The overall impression is of a somewhat parochial view of carbon fibre composites in Germany. Indeed one of the main attractions of the book is that it provides an overview of the state-of-the-art in Germany. Most of the references cited are of German work and as such may not be too familiar to the English language readership. The papers fall into two distinct sections. Seven papers are reviews of materials or techniques whilst six are case studies and two combine both elements. Of the review papers, the first, on processing and uses, is too brief and generalized to be useful. There follow two useful reviews of high strength PAN based carbon fibres and carbon fibres made from pitch. The paper on the surface treatment by Fitzer and Weiss is more detailed than many on this topic. It is a sound fundamental and well balanced treatment and is well referenced. Likewise the contribution on non-.destructive testing by Bilgram and Zimmermarm of MBB. This paper displays a thorough and pragmatic approach to the subject which many engineers should find valuable. There is a reasonable general review of carbon/carbon composites and a rather heavy handed treatment of the benefits to be gained by using hollow fibres. Overall, these review papers are competent but too brief to be really comprehensive and appear to contain little really new material. However, many will fred them useful and up to date as introductions to the topics treated. The most useful and most novel part of the book is a collection of papers which are very brief case studies of particular applications of carbon fibre composites. These are all interesting in that they reveal the design philosophy behind the application. They are all really too brief and much technical data has been omitted but nevertheless they make fascinating reading and, to the reviewer's mind, justify the whole volume. The topics covered are: tension/compression struts; an elevator unit for the Alpha-Jet; a rudder assembly for the Airbus; a military bridge; and, cardan shafts for motor vehicles. These papers follow through the preliminary designs and testing programmes right through to the f'mal hardware, in some cases. Some of the projects such as the Airbus rudder have not yet reached fruition. In virtually all cases there are useful and unexpected lessons to be learnt which would be of value in other projects.
100
The book is completed by chapters on the repair of underground cRp pipelines, the use of oriented fibre materials and on the potential of CVRP for human implant and prosthesis manufacture. In general the translation into English is adequate although inncorrect terminology is sometimes used (eg 'vibration' instead of 'fatigue'). Most readers will have no difficulty in recognizing and correcting these details but they might confuse a reader new to the subject. Likewise many will Fred the frequent minor misspelling and typographical errors irritating but overall the book is quite adequately presented. The diagrams and illustrations are mainly clear and, although small, legible. The book provides a useful insight to current German practice in carbon fibre composites and this alone will recommend it to engineers engaged in similar fields.
IV~.G. Bader
Composite materials: mechanics, mechanical properties and fabrication Edited by: Kozo Kawata and Takashi Akasaka
Japan Society for Composite Materials, Tokyo (1981) £35.00 With about 60 contributions, last year's Japan-US conference on composite materials, held in Tokyo, was evidently a busy meeting. The papers have been put into one volume and the consequent compression of the manuscripts makes reading and interpretation of figures difficult in some cases. Around two-thirds of the contributions are from the host country (the remainder being from the US as the conference title suggests). Thus, the book provides a valuable record of the recent composite progress in both countries, but it is perhaps the emphasis on Japan that makes the book unique in this respect. The quality of the papers is generally high and, as far as the present writer is able to judge, they include much new material. The first 5 sections (15 papers), devoted to Dynamic Behavior, Wave Propagation, Stress Analysis and Mechanical Properties, contain valuable contributions on fracture mechanisms and on the properties of shortfibre composites with special attention paid to fibre orientation. Two papers present interesting examples of the application of the finite element method as a means off exploring the local stress state in composite structures. The three papers on fatigue form a nicely balanced section, the first being a valuable summary of the subject and the other two presenting experimental studies on FRP. In a section devoted to fracture two papers discuss elasto-plastic
COMPOSITES. APRI L 1982
fracture mechanics using the J-integral concept while the third makes a thorough analysis of the statistical approach to fracture. Ten papers under the heading of Metal Matrix Composites provide interesting reading; the applications of recentlyintroduced composites with SiC and A1203 fibres in A1 matrices are described and one paper presents new results on the important problem of thermal cycling. Two examples of metal matrix composites with promising properties can be noted, namely graphite fibre-reinforced bearing metals (produced by flame spraying) with improved wear properties and a Mo-TiC eutectic composite promising high temperature strength and microstructural stability, while possessing some room temperature ductility. For those interested in matrices other than metals and plastics, the book offers one paper on a new type of steel fibre for reinforced mortar, one on the internal friction of silicon nitride and two on fibre-reinforced rubbers. In a section devoted to thermal and environmental problems two contributions deal with the problem of moisture uptake using relatively detailed analytical models; the first treats moisture diffusivity transverse to the fibre direction and the second predicts hygrothermally induced interlaminate stresses. A similar paper presents a predictive model for the thermal conductivity of short-ribbon reinforced microstructures. This section also contains an intriguing experimental study of heat generation during crack propagation in cFaP laminates, using liquid-crystal fdms for temperature measurements. The remainder of the book (20 papers) is devoted to practical applications of composite materials (with emphasis on a- and CFRP) and provides an excellent collection of examples of what advanced composites can be used for and how the special design problems that they pose are being approached. A number of these papers could provide case studies for education purposes and it is perhaps fitting that the book is rounded off by a factual review of current composite education programmes in the USA by R.M. Jones. To summarize, this book suffers from the shortcomings common to most large conference proceedings. However, it provides a relatively well-balanced treatment of the science and technology of advanced fibre composites and has collected a sufficent amount of new useful material to justify its presence on the specialist's bookshelf. R. Warren
Fatigue of fibrous composites A S T M STP 723 (1981) £19.50 The book represents a collection of 17 papers presented at a Symposium held in May 1979, organized by ASTM Committee D-30. Since Committee D-30 is concerned with high-modulus fibres and their composites it is not surprising that the papers reflect a relatively restricted
COMPOSITES. APRIL 1982
range of fibrous materials. The papers are of a high standard and well worth reading. Nevertheless the volume represents activity in aerospace related materials over a limited period of about two years between this and a similar conference. Eleven of the papers are concerned with graphite/epoxy systems, one with silicon carbide-reinforced titanium, one with carbon/carbon, one with glass/epoxy, one with boron/ aluminium, and the remaining two with statistical methods. Seven of the papers can be roughly grouped together because they are concerned with the development of damage or with stress raisers. Phillips considered the effect of the spectrum loading under predominantly compressive conditions and showed that the Miner theory always predicts longer lives than real loading and that interpretation of local damage significantly affects the results. Rosenfeld & Gause considered compression fatigue in the presence of stress raisers, ie open holes and damage produced by impact. He concluded that the compression and fully reversed loading were more damaging than tension/tension loading and that variable amplitude loading demonstrated that Miner's rule is not conservative. Sub-visual damage, produced by impact, degrades compressive strength. Kam reported that the damage occurs at bolt holes in double lapped joints when the bearing stresses are above 50,000 psi and that sealant does not alter hole growth. Whitcomb studied delamination and ply cracking in various laminates produced by both tensile and compressive fatigue loading. Interlaminar shear and peel stresses must be considered when predicting delamination. Fatigue loading, however, generally produces only small stiffness losses and the residual strength can be greater than the original strength. Stinchcomb and others studied damage growth in laminates to determine the constraint effects of adjacent plies. Awerbuch & Hahn looked at off-axis loading and ascertained that there was no strength or modulus degradation up to 10 6 cycles irrespective of off-axis angle. Normalized results for all off-axis conditions were coincident. Rotem & Nelson looked at fatigue behaviour at elevated temperatures developing a predictive method for first failure and total failure in laminates, and claim to predict long term behaviour from short time testing at elevated tempera~ tures. Sun & Chim state that fatigue effects can be retarded due to creep produced during sustained periods of static load. Wang and others, using Weibull statistics, state that proof testing can guarantee a minimum static strengt]a, and to a lesser extent can assure a minimum fatigue life for undirectional graphite/epoxy material. Yang & Jones looked at load sequence effects for glass/epoxy composites and have a theoretical model capable of predicting statistical distribution of fatigue life and the residual strength as effected by load sequence effects. Whitney employed Weibull statistics and power-law representation of the sN curve without a large data base. Tarreja discusses the estimation of Weibull parameters. Only one paper is concerned with structural elements; Rhodes reports on the post buckling behaviour of test panels. The remaining papers are concerned with fatigue mechanisms in boron/aluminium composites and carbon/ carbon composites, and with the fatigue behaviour of silicon carbide-reinforced titanium composites.
M. J. Owen
101
VDI- Verlag GmbH, Dusseldorf (1981) DM 122 This slim volume (282 pp) contains 15 papers which were apparently presented at the second VDI conference on carbon fibre-reinforced plastics, although this is not stated. The authors are drawn from a number of West German, Austrian and Swiss organizations with the exception of one from the USA. The overall impression is of a somewhat parochial view of carbon fibre composites in Germany. Indeed one of the main attractions of the book is that it provides an overview of the state-of-the-art in Germany. Most of the references cited are of German work and as such may not be too familiar to the English language readership. The papers fall into two distinct sections. Seven papers are reviews of materials or techniques whilst six are case studies and two combine both elements. Of the review papers, the first, on processing and uses, is too brief and generalized to be useful. There follow two useful reviews of high strength PAN based carbon fibres and carbon fibres made from pitch. The paper on the surface treatment by Fitzer and Weiss is more detailed than many on this topic. It is a sound fundamental and well balanced treatment and is well referenced. Likewise the contribution on non-.destructive testing by Bilgram and Zimmermarm of MBB. This paper displays a thorough and pragmatic approach to the subject which many engineers should find valuable. There is a reasonable general review of carbon/carbon composites and a rather heavy handed treatment of the benefits to be gained by using hollow fibres. Overall, these review papers are competent but too brief to be really comprehensive and appear to contain little really new material. However, many will fred them useful and up to date as introductions to the topics treated. The most useful and most novel part of the book is a collection of papers which are very brief case studies of particular applications of carbon fibre composites. These are all interesting in that they reveal the design philosophy behind the application. They are all really too brief and much technical data has been omitted but nevertheless they make fascinating reading and, to the reviewer's mind, justify the whole volume. The topics covered are: tension/compression struts; an elevator unit for the Alpha-Jet; a rudder assembly for the Airbus; a military bridge; and, cardan shafts for motor vehicles. These papers follow through the preliminary designs and testing programmes right through to the f'mal hardware, in some cases. Some of the projects such as the Airbus rudder have not yet reached fruition. In virtually all cases there are useful and unexpected lessons to be learnt which would be of value in other projects.
100
The book is completed by chapters on the repair of underground cRp pipelines, the use of oriented fibre materials and on the potential of CVRP for human implant and prosthesis manufacture. In general the translation into English is adequate although inncorrect terminology is sometimes used (eg 'vibration' instead of 'fatigue'). Most readers will have no difficulty in recognizing and correcting these details but they might confuse a reader new to the subject. Likewise many will Fred the frequent minor misspelling and typographical errors irritating but overall the book is quite adequately presented. The diagrams and illustrations are mainly clear and, although small, legible. The book provides a useful insight to current German practice in carbon fibre composites and this alone will recommend it to engineers engaged in similar fields.
IV~.G. Bader
Composite materials: mechanics, mechanical properties and fabrication Edited by: Kozo Kawata and Takashi Akasaka
Japan Society for Composite Materials, Tokyo (1981) £35.00 With about 60 contributions, last year's Japan-US conference on composite materials, held in Tokyo, was evidently a busy meeting. The papers have been put into one volume and the consequent compression of the manuscripts makes reading and interpretation of figures difficult in some cases. Around two-thirds of the contributions are from the host country (the remainder being from the US as the conference title suggests). Thus, the book provides a valuable record of the recent composite progress in both countries, but it is perhaps the emphasis on Japan that makes the book unique in this respect. The quality of the papers is generally high and, as far as the present writer is able to judge, they include much new material. The first 5 sections (15 papers), devoted to Dynamic Behavior, Wave Propagation, Stress Analysis and Mechanical Properties, contain valuable contributions on fracture mechanisms and on the properties of shortfibre composites with special attention paid to fibre orientation. Two papers present interesting examples of the application of the finite element method as a means off exploring the local stress state in composite structures. The three papers on fatigue form a nicely balanced section, the first being a valuable summary of the subject and the other two presenting experimental studies on FRP. In a section devoted to fracture two papers discuss elasto-plastic
COMPOSITES. APRI L 1982
fracture mechanics using the J-integral concept while the third makes a thorough analysis of the statistical approach to fracture. Ten papers under the heading of Metal Matrix Composites provide interesting reading; the applications of recentlyintroduced composites with SiC and A1203 fibres in A1 matrices are described and one paper presents new results on the important problem of thermal cycling. Two examples of metal matrix composites with promising properties can be noted, namely graphite fibre-reinforced bearing metals (produced by flame spraying) with improved wear properties and a Mo-TiC eutectic composite promising high temperature strength and microstructural stability, while possessing some room temperature ductility. For those interested in matrices other than metals and plastics, the book offers one paper on a new type of steel fibre for reinforced mortar, one on the internal friction of silicon nitride and two on fibre-reinforced rubbers. In a section devoted to thermal and environmental problems two contributions deal with the problem of moisture uptake using relatively detailed analytical models; the first treats moisture diffusivity transverse to the fibre direction and the second predicts hygrothermally induced interlaminate stresses. A similar paper presents a predictive model for the thermal conductivity of short-ribbon reinforced microstructures. This section also contains an intriguing experimental study of heat generation during crack propagation in cFaP laminates, using liquid-crystal fdms for temperature measurements. The remainder of the book (20 papers) is devoted to practical applications of composite materials (with emphasis on a- and CFRP) and provides an excellent collection of examples of what advanced composites can be used for and how the special design problems that they pose are being approached. A number of these papers could provide case studies for education purposes and it is perhaps fitting that the book is rounded off by a factual review of current composite education programmes in the USA by R.M. Jones. To summarize, this book suffers from the shortcomings common to most large conference proceedings. However, it provides a relatively well-balanced treatment of the science and technology of advanced fibre composites and has collected a sufficent amount of new useful material to justify its presence on the specialist's bookshelf. R. Warren
Fatigue of fibrous composites A S T M STP 723 (1981) £19.50 The book represents a collection of 17 papers presented at a Symposium held in May 1979, organized by ASTM Committee D-30. Since Committee D-30 is concerned with high-modulus fibres and their composites it is not surprising that the papers reflect a relatively restricted
COMPOSITES. APRIL 1982
range of fibrous materials. The papers are of a high standard and well worth reading. Nevertheless the volume represents activity in aerospace related materials over a limited period of about two years between this and a similar conference. Eleven of the papers are concerned with graphite/epoxy systems, one with silicon carbide-reinforced titanium, one with carbon/carbon, one with glass/epoxy, one with boron/ aluminium, and the remaining two with statistical methods. Seven of the papers can be roughly grouped together because they are concerned with the development of damage or with stress raisers. Phillips considered the effect of the spectrum loading under predominantly compressive conditions and showed that the Miner theory always predicts longer lives than real loading and that interpretation of local damage significantly affects the results. Rosenfeld & Gause considered compression fatigue in the presence of stress raisers, ie open holes and damage produced by impact. He concluded that the compression and fully reversed loading were more damaging than tension/tension loading and that variable amplitude loading demonstrated that Miner's rule is not conservative. Sub-visual damage, produced by impact, degrades compressive strength. Kam reported that the damage occurs at bolt holes in double lapped joints when the bearing stresses are above 50,000 psi and that sealant does not alter hole growth. Whitcomb studied delamination and ply cracking in various laminates produced by both tensile and compressive fatigue loading. Interlaminar shear and peel stresses must be considered when predicting delamination. Fatigue loading, however, generally produces only small stiffness losses and the residual strength can be greater than the original strength. Stinchcomb and others studied damage growth in laminates to determine the constraint effects of adjacent plies. Awerbuch & Hahn looked at off-axis loading and ascertained that there was no strength or modulus degradation up to 10 6 cycles irrespective of off-axis angle. Normalized results for all off-axis conditions were coincident. Rotem & Nelson looked at fatigue behaviour at elevated temperatures developing a predictive method for first failure and total failure in laminates, and claim to predict long term behaviour from short time testing at elevated tempera~ tures. Sun & Chim state that fatigue effects can be retarded due to creep produced during sustained periods of static load. Wang and others, using Weibull statistics, state that proof testing can guarantee a minimum static strengt]a, and to a lesser extent can assure a minimum fatigue life for undirectional graphite/epoxy material. Yang & Jones looked at load sequence effects for glass/epoxy composites and have a theoretical model capable of predicting statistical distribution of fatigue life and the residual strength as effected by load sequence effects. Whitney employed Weibull statistics and power-law representation of the sN curve without a large data base. Tarreja discusses the estimation of Weibull parameters. Only one paper is concerned with structural elements; Rhodes reports on the post buckling behaviour of test panels. The remaining papers are concerned with fatigue mechanisms in boron/aluminium composites and carbon/ carbon composites, and with the fatigue behaviour of silicon carbide-reinforced titanium composites.
M. J. Owen
101