This volume is a collection of the papers given at the workshop on Fracture Scaling, held at the University of Maryland, USA, 10-12 June 1999, under the sponsorship of the Office of Naval Research, Arlington, VA, USA. These papers can be grouped under five major themes: Micromechanical analysis Size effects in fiber composites Scaling and heterogeneity Computational aspects and nonlocal or gradient models Size effects in concrete, ice and soils . This workshop is the result of a significant research effort, supported by the Office of Naval Research, into the problems of scaling of fracture in fiber composites, and generally into the problems of scaling in solid mechanics. These problems, which are of interest for many materials, especially all quasibrittle materials, share similar characteristics. Thus, progress in the understanding of scaling problems for one material may help progress for another material. This makes it clear that a dialogue between researchers in various fields of mechanics is highly desirable and should be promoted. In view of this, this volume should be of interest to researchers and advanced graduate students in materials science, solid mechanics and civil engineering.

Within the Solid Mechanics Program at the Office of Naval Research (ONR), our primary mission is to establish a basic research program which addresses the funda mental issues in solid mechanics where a clear scientific understanding is lacking. Our approach involves first identifying the various scales at which material and structural response and failure occur. Within each level of behavior we address the basic mechanical phenomena for which a clear physical description is not available. ONR's program emphasizes experimental research to identify and quantify the interacting behavior and response mechanisms. Theoretical and computational approaches are developed to explain the details of the physical processes and to establish the technology necessary to control the thermomechanical behavior of materials and structures. Within the Department of Defense, it is a natural evolution that all new systems must generally operate in more demanding environments than the systems they replace. Thus, structural designers are pushed towards lighter weight, precision structures utilizing new materials. In such an environment, structural design mar gins simultaneously shrink and become more critical. Such trends make it essential that a well founded scientific base for the nondestructive detection and assessment of subcritical flaws in structural materials and structures exist. Within the ONR Solid Mechanics Program we are interested in both the identification of flaws and assessment of their degree of criticality."

Within the Solid Mechanics Program at the Office of Naval Research (ONR), our primary mission is to establish a basic research program which addresses the funda mental issues in solid mechanics where a clear scientific understanding is lacking. Our approach involves first identifying the various scales at which material and structural response and failure occur. Within each level of behavior we address the basic mechanical phenomena for which a clear physical description is not available. ONR's program emphasizes experimental research to identify and quantify the interacting behavior and response mechanisms. Theoretical and computational approaches are developed to explain the details of the physical processes and to establish the technology necessary to control the thermomechanical behavior of materials and structures. Within the Department of Defense, it is a natural evolution that all new systems must generally operate in more demanding environments than the systems they replace. Thus, structural designers are pushed towards lighter weight, precision structures utilizing new materials. In such an environment, structural design mar gins simultaneously shrink and become more critical. Such trends make it essential that a well founded scientific base for the nondestructive detection and assessment of subcritical flaws in structural materials and structures exist. Within the ONR Solid Mechanics Program we are interested in both the identification of flaws and assessment of their degree of criticality."