The result of the authors' 40 years of experience in durability testing, this book describes the advanced testing methodology based on the viscoelasticity of matrix polymer. After a short introduction to the viscoelastic behavior of fiber-reinforced plastics, the text goes on to review in detail the concepts of static, fatigue and creep strengths in polymer composites. An application-oriented approach is adopted such that the concepts developed in the book are applied to real-life examples. Indispensable information for materials scientists and engineers working in those industrial sectors is concerned with the development and safe use of polymer composite-based products.