Reliability as a Materials Property

The introduction of new materials for use in load-bearing applications in a marketplace with very high standards of reliability poses an important design problem because designers had come to take the reliability of their materials for granted. Many decades of manufacturing development brought the commonly used metals to their present perfection. Given the even larger number of processing and innate property variables of the new engineering plastics and composites, they actually exhibit considerably wider dispersions of instantaneous strength properties as well as of fatigue characteristics. The data assembled in this paper suggest that one cannot foretell at present where the ultimately attainable reliability limits of different kinds of composites may be. Current attainments are then compared with the minimum reliability demands of some of the economically important applications foreseen for composites. Can the difference be made up by clever design or only by improved materials?