CALCULATION, MEASUREMENT, AND CONTROL OF INTERFACE STRENGTH IN COMPOSITES

Strength and energy criteria for interface delamination are given for composite systems involving anisotropic fibers. The tensile strength of planar interfaces is measured with a modified laser spallation experiment involving a laser Doppler displacement interferometer. The technique for achieving desired interface properties is demonstrated on an Nb/Al2O3 interface. In the as-deposited state, the strength is determined to be 0.28 GPa. The interface strength is controlled with sputter-deposited Cr and Sb interlayers. The strength of Nb/Al2O3 interfaces varies from 0.28 to 0.35 GPa when the Cr layer thickness varies from 1 to 50 angstrom. The strength is reduced to 0. 16 GPa with Sb thickness of 70 angstrom.