Abstract
Detection and measurement of sub-micron boundary layers developed between phases in composites was achieved by using the method of caustics. These singular curves were detected on a reference screen receiving the refracted rays of a parallel-light beam at these boundary layers, which were recognized as possessing slightly different values of their re fractive indices due to constraints between phases.
Utilizing the theory of formation of caustics for substances with constant refractive in dices, but arbitrary and smooth boundary surfaces, the direct and inverse affinities be tween caustics and the refracting surfaces were established.
This theory was applied to the inverse problem of defining from the caustic the zone of variation of the refractive surface at the interfaces between main phases of composites. In this way the extent of the mesophase in a fiber composite may be accurately established. Experimental evidence is in agreement with existing theories of the existence and extent of mesophases.
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