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APPENDIX I WORKSHOP PURPOSE AND PROGRAM (From Program Announcement) PURPOSE AND SCOPE The broad field of polymer science and engineering offers many opportunities for major advances. There are many products that fall short of military and NASA requirements. In the case of polymeric adhesives, there are both problems and promise. Some restricting factors are the limited ability to withstand high temperatures (above 350Â°C), cryogenic temperatures, and cyclic loading. The ability to detect "weak" bonds and to predict service life are both very poor, and technology development is needed before more structural uses develop. Interesting new polymers have recently been developed, and understanding of surface science is improved. Therefore it appears that major advances in adhesive joining technology are possible that can lead to useful and needed products. Adhesive formulations alone are not at issue. As reflected in the workshop program, advances in evaluation, stress analysis, and interface reactions can all lead to progress in the field. The unclassified workshop will highlight some of the opportunities to permit the committee to make recommendations to DOD and NASA as to promising research directions. AGENDA May 3, 1984 Lecture Room 9:00 Welcome Serge Gratch Introduction 9:30 Interests and Activities of the Department Leighton Peebles of Defense and the National Aeronautics and Space Administration 10:15 Break 10:30 Overview of Virginia Polytechnic Institute Halbert Brinson and State University Program Review/Workshop Melvin Kanninen J. E. McGrath 11:30 Lunch 39
38 static failure due to material degradation. Potential failure mechanisms and their associated stress and environmental dependence must be characterized for each adhesive prior to application. Fracture mechanics has been demonstrated to be a viable tool for characterizing and predicting static strength and cyclic debonding of adhesive joints containing initial debonding. Several viable nonlinear viscoelastic models exist for the prediction of long-term creep rupture. There is general agreement that emphasis should be placed on defining the threshold region for fatigue damage and creep rupture and then using these data as upper design limits. The failure mechanisms of several frequently used structural adhesives when subjected to severe environments needs to be established. Such determinations will also permit the development of an experimental data base, which is needed. One use of a long-time durability data base is to verify accelerated characterization test methods. The testing mentioned above will help define the relative influences of viscoelasticity (creep), cyclic fatigue, and static loading in severe environments, and also to characterize fatigue and creep interactions.