Phase Boundary Surface
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Phase boundary surface
Formation of phase boundaries
Where regions of different structures and/or varying compositions (different phases) meet, phase boundaries are formed. The area between the phases is referred to as an interface. A specific type of interface is the surface of solid bodies that borders on the air (i.e. the solid–gas phase boundary).
Types of phase boundaries
If two phases differ only slightly in structure, one structure may merge into the other (in crystalline structures, this results in lattice distortions) The interface is described as coherent. If the differences in the structures are greater, the interface is partially coherent. If the adjacent phases differ so greatly in their structure that no further adaptation can take place, the interface is incoherent. The energy of an interface increases from the coherent to the incoherent state.
Formation of boundary layers in fibre-reinforced plastics
In fibre-reinforced plastics, interfaces form between the fibre and the matrix at the points where they meet (see also: fibre–matrix adhesion). These interfaces involve the interactions between the fibre and the matrix and transmit the stresses between them. The concept of the interface implies a two-dimensional view of the interaction effects. In contrast, a three-dimensional view is referred to when an interphase of finite thickness is introduced. The properties of the interfacial layer in a fibre-reinforced composite (see also: testing of composite materials) differ from those of the fibre and the matrix. The interfacial layer, in turn, forms continuous transitions to both the fibre and the matrix, so that the physical, chemical and mechanical properties also change continuously (steadily) rather than abruptly (discontinuously). The formation of the boundary layers depends on the processing conditions during the manufacture of the composites and is also dependent on the respective matrix (thermoplastics, thermosets and elastomers).
See also
- Surface tension and interfacial tension
- Microscopic structure
- GRIFFITH's theory
- Crack toughness
- Fracture
References
- Schatt, W. (Ed.): Einführung in die Werkstoffwissenschaft. Deutscher Verlag für Grundstoffindustrie, Leipzig (1975), 2nd Edition, p. 81 (see AMK-Library under L 3-1)
- Schatt, W., Worch, H. (Eds.): Werkstoffwissenschaft. Deutscher Verlag für Grundstoffindustrie, Stuttgart (1996) (ISBN 3-342-006-75-7; see AMK-Library under L 3-2)