In writing this monograph, the aim has been to consider the mechanical properties of the wide range of materials now available in such a way as to start with the fundamental nature of these properties and to follow the discussion through to the point at which the reader is able to comprehend the significance or otherwise of the large amounts of data now available in design manuals and other compilations. In short, it is hoped that this volume will be used as a companion to these data compilations and as an aid to their interpretation. In attempting to cover such a wide field, a large degree of selection has been necessary, as complete volumes have been written on topics which here have had to be covered in a few pages or less. It is inevitable that not everyone will agree with the choice made, especially if it is his own subject which has been discussed rather briefly, and the author accepts full res ponsibility for the selection made. The book is written at a level which should be easily followed by a university graduate in science or engineer ing, although, if his background has not included a course in materials science, some groundwork may be lacking.

Cryogenics is an emerging technology filled with promises. Many cryogenic systems demand the use of nonmetallics and composites for adequate or increased performance. Thermal and electrical insulations, potting for superconducting magnets' mechanical sta bility, and composite structures appear to be some of the most significant applications. Research on nonmetallics at cryogenic temperatures has not progressed to the degree of research on metals. Nor can room temperature research be extrapolated to low tempera tures; most polymers undergo a phase transformation to the glassy state below room temperature. Research by producers, for the most part, has not been prac tical, because, except for LNG applications, the market for large material sales is not imminent. There are, however, many government stimulated developmental programs. Research on nonmetallics thus is dictated by development project needs, which require studies orien ted toward prototype hardware and specific objectives. As a result, research continuity suffers. Under these conditions, periodic topical conferences on this subject are needed. Industry and uni versity studies must be encouraged. Designers and project research material specialists need to exchange experiences and data. Low temperature-oriented research groups, such as the National Bureau of Standards and the Institute for Technical Physics - Karlsruhe, must contribute by assisting with fundamentals, interpreting proj ect data, and contributing to project programs through their materials research.