Heterogeneous vs. molecular composites

The well known Tsai-Halpin equation [1] describes the dependence of the modulus of a composite on that of the basis materials, the volume fraction of the fibers and their aspect ratio. In these composites the fibers carry the load and the matrix distributes it. Fiber reinforced thermosets have a wide range of technical applications and play an important role in self-supporting, low-weight constructions. 

Equation (9.4) is often used as a crude mixing rule the closer L/D approaches infinity, the better results it provides. 

The main drawback of these composites lies in their processability high quality laminates often have to be formed by hand, short-fiber filled EPs can be sprayed or extruded but there is high abrasion of the processing equipment. Another disadvantage of these composites might occur when the composite has to be recycled again and the filler has to be removed from the polymer. 

This great variety of rigid or semirigid polymers opens a wide field for the creation of new polymers by combining them with EPs. Combining here means producing a blend. Such a blend may be a phase 

AG is the Gibbs free energy of mixing and (j) is the volume fraction of the component under consideration. 

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