Trapped Acoustic Modes for Adhesive Strength Determination,
ROCKWELL INTERNATIONAL THOUSAND OAKS CA SCIENCE CENTER
Pagination or Media Count:
The experiments discussed in this report were designed to consider the case in which the acoustic energy propagates parallel to the metal-adhesive interface so that small differences in the boundary conditions could accumulate over a large interaction distance. Calculations of the propagating modes in a metal-adhesive-metal sandwich were carried out so that a prediction of the particular modes that would be most sensitive to the interface properties could be made. Several different experimental approaches to exciting and detecting these particular modes were investigated, but none proved immediately useful because other, undesired modes usually obscured the features that were to be measured. However, the theoretical studies also predicted a standing wave mode that was sensitive to the adhesion quality so special experiments were designed to compare the resonant frequency of this mode with the mechanical strength of samples prepared with a variety of adhesive bond strengths. These tests were successful and a good correlation between frequency and strength was discovered.