Role of Particle-Matrix Interface in the Deformation and Fracture Behaviour of Filled Epoxy Resins

As a result of their superior mechanical, chemical, and electrical properties particulate-filled epoxies are finding widespread use in the fabrication of a large number of engineering components, one important example being as electrical insulators for the power industry. Since these materials are mainly subjected to continuous mechanical loads (in addition to a continuous dielectrical stress), there is an apparent need first to understand and then to predict the processes of deformation and fracture during long-term loading conditions. A few years ago, the respective material science knowledge was very limited, and design was mainly based on experience and purely empirical work. During recent years, however, a rather comprehensive understanding of the short and long-term deformation and fracture behaviour of these brittle, highly cross-linked polymers, especially of silica-filled anhydride-cured epoxies, has been accumulated. This holds particularly for the understanding of their creep behaviour, i.e. the deformation-induced volume damage and the mechanisms which are responsible for creep failure. In this article, a survey will given on the applications, and the deformation and fracture behaviour of particulate-epoxies. In particular, the role of particle-matrix interface in connexion with deformation, fracture, and creep behaviour and the related deformation-induced volume damage is discussed. A complete understanding of the role of the particle-matrix interface is still lacking and, therefore, a coherent description is not possible, and the true practical value of a filler surface treatment is not yet known. However, the following can be said: local as well as global debonding between matrix and filler should be prevented; local debonding tends to act as a critical flaw (in a fracture mechanics sense) and leads to brittle failure. Global debonding is equivalent to creep damage and leads to premature failure of the respective component