framework for predicting long-term performance of adhesive joints under the influence of various environmental factors.

The advances in adhesion chemistry and control of surface functional groups lead naturally to the design of interfaces between the matrix and the reinforcement in composites. Through the study of the chemistry of new generations of coupling agents and properties (e.g., tensile and impact strength), enhanced performance of structural composites may be achieved. Higher-molecular-weight coupling agents could provide affinity with both the matrix and the reinforcement and better matching of the mechanical properties of the two components. A better understanding of the chemistry of composite interfaces will enable rational design of high-performance materials and control of aging processes that limit applications. Owing to the interplay of chemical and mechanical factors, support of interdisciplinary programs that offer useful synergies should be given special priority.

There is a need for long-fiber composites that can be changed in shape (i.e., can be made formable) after the matrix is fully or partially cured. The introduction of thermoplastic matrices and possibly liquid crystalline matrices suggests a possible route to more formable composites and could broaden the range of applications of these materials. Fundamental studies of deformation and flow processes in such systems could lead to new classes of materials with useful structural properties.