Within the last two decades fracture theory has been one of the most rapidly advancing fields of continuous media mechanics. Noteworthy suc cess has been achieved in linear fracture mechanics where the propagation of the macrocrack in elastic materials is under study. However, fracture of materials is by no means a simple process since it involves fracture of structural elements ranging from atomic sizes to macrocracks. To obtain all information about how and why materials fail, all stages of the process must be studied. For a long time both mechanical engineers and physicists have been concerned with the problem of the fracture of solids. Unfortunately, most of their work has been independent of the others. To solve the problem not only requires the minds and work of mechanical engineers and physicists but chemists and other specialists must be consulted as well. In this book we will consider some conclusions of the "physical" and "mechanical" schools acquired by the A. F. Joffe Physics-Technical Institute of the USSR Academy of Sciences in Leningrad and the Institute of Polymer Mechanics of Latvian SSR Academy of Sciences in Riga. The methods for studying the phenomena of fracture applied at both Institutes are different yet complimentary to one another; the materials tested are also sometimes different."

The Second USA-USSR Symposium on Fna~e 06 Compo~~e Mat~aGBPh took place at Lehigh University, Bethlehem, Pennsylvania, during 9-12 March, 1981. This bilateral program between the U. S. and Soviet Union was organized by Professor George C. Sih of the Institute of Fracture and Solid Mechanics at Lehigh Uni versity and Dr. Vitauts P. Tamuzs of the Institute of Polymer Mechanics of the Academy of Sciences of the Latvian SSR in Riga. The First Symposium was held in 1978 at Jurmala near the coast of Riga Bay. The primary reasons for initiating this series of Symposia were to dissemi nate present knowledge, to promote interchange of ideas, and to stimulate addi tional studies on the development of composite materials between the U. S. and USSR. Both countries have a vested interest in developing the capability to assess and utilize the attractive mechanical properties of composites so that they can be tailor-made to meet specific design requirements. Despite the in creasing number of published papers and articles, there is no communication more effective than on a person-to-person basis. It is with this objective in mind that a small group of engineers and scientists from the U. S. and USSR have planned to meet every two years to report recent progress on composite material research. The size of this group is approximately sixty (60) participants. The presentation involves about forty (40) technical papers which are published in volume.

The Second USA-USSR Symposium on Fna~e 06 Compo~~e Mat~aGBPh took place at Lehigh University, Bethlehem, Pennsylvania, during 9-12 March, 1981. This bilateral program between the U. S. and Soviet Union was organized by Professor George C. Sih of the Institute of Fracture and Solid Mechanics at Lehigh Uni versity and Dr. Vitauts P. Tamuzs of the Institute of Polymer Mechanics of the Academy of Sciences of the Latvian SSR in Riga. The First Symposium was held in 1978 at Jurmala near the coast of Riga Bay. The primary reasons for initiating this series of Symposia were to dissemi nate present knowledge, to promote interchange of ideas, and to stimulate addi tional studies on the development of composite materials between the U. S. and USSR. Both countries have a vested interest in developing the capability to assess and utilize the attractive mechanical properties of composites so that they can be tailor-made to meet specific design requirements. Despite the in creasing number of published papers and articles, there is no communication more effective than on a person-to-person basis. It is with this objective in mind that a small group of engineers and scientists from the U. S. and USSR have planned to meet every two years to report recent progress on composite material research. The size of this group is approximately sixty (60) participants. The presentation involves about forty (40) technical papers which are published in volume.

Within the last two decades fracture theory has been one of the most rapidly advancing fields of continuous media mechanics. Noteworthy suc cess has been achieved in linear fracture mechanics where the propagation of the macrocrack in elastic materials is under study. However, fracture of materials is by no means a simple process since it involves fracture of structural elements ranging from atomic sizes to macrocracks. To obtain all information about how and why materials fail, all stages of the process must be studied. For a long time both mechanical engineers and physicists have been concerned with the problem of the fracture of solids. Unfortunately, most of their work has been independent of the others. To solve the problem not only requires the minds and work of mechanical engineers and physicists but chemists and other specialists must be consulted as well. In this book we will consider some conclusions of the "physical" and "mechanical" schools acquired by the A. F. Joffe Physics-Technical Institute of the USSR Academy of Sciences in Leningrad and the Institute of Polymer Mechanics of Latvian SSR Academy of Sciences in Riga. The methods for studying the phenomena of fracture applied at both Institutes are different yet complimentary to one another; the materials tested are also sometimes different."