With increasing use of polymers in sophisticated industrial applications, it is essential that mechanical engineers have a solid understanding of these compounds. This text provides a thorough introduction to polymers from a mechanical engineering perspective, treating stresses and deformations in structural components made of polymers. The authors discuss the time-dependent response of polymers and its implications for mechanical response; mechanical response for both time-dependent and frequency-dependent material properties; and the application of the stress-strain-time relation to determine stresses and deformations in structures. With numerous examples and extensive illustrations, this book will help advanced undergraduate and graduate students, as well as practicing mechanical engineers, to make effective use of polymeric materials.