I am extremely honoured and delighted that so many colleagues would wish to dedicate a paper and, hence, go through the labour of writing and preparing illustrations as a celebration of my birthday. I am very grateful to all the authors and editors.
I read physics as an undergraduate. In those days, we did practical work and I examined Bitter patterns, which led to an interest in sub-grains. I read Fred Seitz's Physics of Metals who, with Tom Reid, wrote the first paper on dislocations from the United States. Through working on an X-ray micro-beam technique suggested by Sir Lawrence Bragg, I developed an interest in micro-structure and, thus, in the mechanical properties of materials. I published papers on work hardening and on ways of strengthening metals and alloys. Through that work and in attempts to understand rapid work hardening, I was led to an interest in composite materials.
High-strength fibrous composites exemplify the development and convergence of metallurgy, ceramics and plastics in Materials Science and Materials Science and Engineering.
After working in the US during the middle to late 1950s, I returned to Cambridge to teach a new course on ceramic materials in the Metallurgy Department. I remember Kingsley Williamson remarking: “…you have done very well Tony… where did you get the science from?” Through funding obtained by A.H. Cottrell, I worked with Clive Baker, Earl Freise and Murray Gillin on graphite in the development of the high temperature nuclear reactor. I got to know Willy Watts, known for work on pyrolytic graphite, some years before he, with Philips and Johnson, developed carbon fibres from polyacrylonitrile. I busied myself with my students in studying the mechanical properties of what I subsequently called inherently strong solids – strongly covalently bound elements or (mainly binary) compounds.
In the early 1960s, the principles of composite materials or fibrous composite materials were well known by certain groups of materials engineers due to the success of glass-reinforced plastic. This material was strong – good for pressure vessels and rocket motor cases – but lacked stiffness. First, the whisker crystals of strong solids and then fibres of these, alumina, boron and silicon carbide on tungsten or tungsten by itself were investigated and then the invention of carbon fibres. They possessed both stiffness and strength – but did we have toughness?
This is still the problem with all strong engineering materials: how to understand breaking and the details controlling toughness against fracture of a solid. With my knowledge of methods of calculating ideal strength, i.e. the strength of a piece of material with no imperfections, and my research on the strength of metals, I wrote a small book, Strong Solids, of which I am very proud and which had a considerable influence at the time. A third edition with Norman Macmillan appeared in the 1980s. With Bill Tyson, I calculated the ideal strength and developed a general criterion for distinguishing brittle and ductile crystals with Cottrell and Tyson. Mick Brown was an enormous help
When my book was published, I left Cambridge and went to the National Physical Laboratory. There, my collaborators on ceramics and composites: Groves, Cooper, Tyson among others were replaced by new colleagues at NPL: Neil McCartney, John Aveston and John Sillwood, John Lockett and Alastair Johnson (the latter two, reformed mathematicians). Sergei Mileiko came to work with me from the, then, Soviet Union, pioneering work with Ken Street on creep of composites, a field in which he is now a world leader. At the NPL, we stimulated full-scale measurement of the elastic properties of fibre composites and interacted with people who had a knowledge of polymers. Cooper came with me to NPL and, there, he discovered multiple fracture, which I was able to interpret via experiments. It is multiple fractures, under various names, which enables the manifest toughness of composite materials. A.H. Cottrell (that master of metallurgical sciences) remarked that the discovery, that composites are tough because they break up under stress in a controlled way, was a huge surprise in Materials Science. The field of damage mechanics is now a major research area in the properties of composite materials.
During my period at NPL, I was seconded for a time to ICI and so gained some insight into commercialisation of new materials. I worked with Derek Birchall and admired Kevin Kendall's work; it was a wonderful period, the 1980s, as the major chemical companies became interested in new materials. When my secondment to the ICI terminated in 1975, I become Vice Chancellor of the University of Surrey but retained a position as corporate consultant with the company until its dissolution into ICI & Zeneca in the mid-1990s. Though holding an important administrative position at Surrey, I was also fortunate to be able to continue my research. Being essentially an experimentalist, I need to know what is happening at the bench and my friendship and collaboration with John Aveston and Neil McCartney enabled this throughout these years. Tsu-Wei Chou's appointment to Surrey stimulated an interest in composite materials, where there was an energetic group of composite researchers unconnected with my personal efforts; for example, Dave Hannant on cement, Len Hollaway on light weight structures and Frank Jones on polymer matrices (Frank and I barely knew each other at Surrey). Both Ali Argon and I worked on the properties of cement for a while but his interests in Materials Science are incredibly catholic.
I watched Materials Science thrive but my main interest was in composite materials. I have watching the enormous and steady growth of this field, culminating in wonderful aircraft such as the Airbus A380 and the Boeing 787, which will soon be flying commercially. It has been awe-inspiring to watch the development of a totally new construction material – high strength carbon fibre. Some 35,000 tonnes of this material are produced annually. It all stemmed from Willy Watts’ idea after the Royal Society Conference on new materials in 1963 at which I spoke on the lack of a highly stiff carbon fibre and which, from my knowledge of atomic bonding, knew ought to exist.
Over the years, I have been very lucky to assist and learn from engineers such as Tony Bunsell, Ramesh Talreja. John Hart-Smith and Murray Scott. I feel particularly honoured that they wished to contribute to this special issue.
After my time at Surrey, I returned to Cambridge and was made very welcome by the Department now known as Materials Science and Metallurgy. My serene wife, Christina, had died and so I busied myself once more with experiments on composite materials, having been given the hospitality of the Gordon Laboratory (named after Jim Gordon, a prophet on the possibilities of composite materials) by Bill Clyne. During this period, I enjoyed working with Bill Clegg, using composite material to invent a material of negative thermal expansion coefficient, understanding how to use composite principles to combine controlled thermal expansion coefficient with high electrical conductivity and resolving one or two theoretical problems.
With Graham Parkhouse, I finally determined how a fibrous composite with a particular microstructure showed isotropic elastic properties and, allied to this, the optimum arrangement of fibres for maximum packing. An interest in controlling thermal expansion led to cooperation with Ludger Weber (EPFL, Switzerland) and back to what are now called particulate composites, which, before the emergence of composite materials as a subject, were much in vogue and called dispersion strength materials with high volume fractions of dispersed phase.
One of the problems of fibre mechanics has been the lack of closed-form solutions for the elastic properties of binary aligned composites and particulates. Neil McCartney, with minor assistance from me, has recently shown how closed-form solutions can be obtained for the elastic properties and some transport properties of particulate and aligned composites using the Maxwell formulation of 1873. What wonderful insight Maxwell had.
The papers in this special issue touch upon various episodes I have referred to above. I know I have not included many people who have helped me and to whom I remain very grateful. Nor have I mentioned in this Preface my interactions with all of those who have so kindly contributed to this volume.
During the last year or so, I have interested myself in the science of climate and man's putative effects on climate. This is a composite of composite subjects too important to be left solely to climate scientists and I urge all natural scientists to concern themselves in the details. My own efforts appear in Energy and Environment, Vol. 21, No. 6 which will be published at the same time as this special issue.