| Summary: | After explaining the importance of fracture mechanics, three kinds of fracture mechanics are distinguished and characterized—brittle, ductile and quasibrittle. The last is a relatively more recent branch of fracture mechanics dealing with heterogeneous materials with brittle constituents, which include concrete, many rocks, tough ceramics, fiber composites, sea ice, stiff soils, rigid foams, wood, etc. They are called quasibrittle because in small structures they exhibit limited ductility. While brittle and ductile fracture has traditionally been modeled as line cracks, the quasibrittle fracture mechanics is best described in terms of a band of softening damage. This is particularly important for capturing the effect of crack parallel stresses on the fracture energy, recently revealed by a new type of test, called the gap test. The most important characteristic of quasibrittle materials is an energetic size effect on structure strength which, depending on the structure type, may either dominate or require amalgamation with the classical statistical size effect. In closing, various important applications are pointed out. Each chapter includes application examples and is accompanied by extensive sets of exercise problems, needed for teaching a course.
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