This book provides the first comprehensive review of its kind on the long-term behaviour of composite materials and structures subjected to time variable mechanical, thermal, and chemical influences, a subject of critical importance to the design, development, and certification of high performance engineering structures. Specific topics examined include damage, damage characterization, and damage mechanics; fatigue testing and evaluation; fatigue behaviour of short and long fibre reinforced polymer and metal matrix materials; viscoelastic and moisture effects; delamination; statistical considerations; the modeling of cumulative damage development; and life prediction. The volume provides an extensive presentation of data, discussions, and comparisons on the behaviour of the major types of material systems in current use, as well as extensive analysis and modeling (including the first presentation of work not found elsewhere). The book will be of special interest to engineers concerned with reliability, maintainability, safety, certification, and damage tolerance; to materials developers concerned with making materials for long-term service, especially under severe loads and environments, and to lecturers, students, and researchers involved in material system design, performance, solid mechanics, fatigue, durability, and composite materials. The scope of the work extends from entry level material to the frontiers of the subject.