JEAN-PIERRE PASCAULT is Professor of Chemical and Materials Science, Institut National des Sciences Appliquees de Lyon and National Scientific Research Council, Villeurbanne, France. The author of 250 journal articles and book chapters, he holds 25 patents and is President of the French Polymer Association (2001-2004). A member of the American Chemical Society, the Materials Research Society, and the Polymer Network Group, he received the Ph.D. degree (1970) from the University of Lyon, France. HENRY SAUTEREAU is Professor of Chemical and Materials Engineering, Institut National des Sciences Appliquees de Lyon and National Scientific Research Council, Villeurbanne, France. The author of more than 100 journal articles and book chapters, he is a member of the French Polymer Association, the Polymer Network Group, and the European Structural Integrity Society. He received the Ph.D. degree (1976) in chemistry from the University of Lyon, France. JACQUES VERDU is Professor and Director of Laboratoire de Transformation et de Vieillissement des Polymeres, Ecole 'Nationale Superieure d' Arts et Metiers, Paris, France. The author of nearly 200 journal articles and book chapters, he is a member of the French Polymer Association and the Association pour Jes Materiaux Composites (AMAC). He received the Ph.D. degree (!976) from the Universite Pierre et Marie Curie, Paris, France. ROBERTO J. J. WILLIAM_S is Professor, National University of Mar del Plata, Argentina, and Member of the National Research Council (CONICET), Argentina. The author of more than 150 professional papers and book chapters, he is a member of the American Chemical Society and the Polymer Network Group. He received the Ph.D. degree (1972) from the National University of La Plata, Buenos Aires, Argentina.