Multiple Cracking and Interface Debonding in a Brittle Film on a Ductile Rod

A test technique was developed to measure interfacial shear strength through observation of crack densities in bimaterial concentric cylinders. Multiple cracking and debonding were observed in a model ductile-brittle pair of aluminum rods with soda-silicate cement coatings and the results compared to a system where the interface was modified by a polymeric interphase layer. A shear lag analysis was used to relate the observed crack densities to the interfacial shear strength. Four point bend tests were performed on monolithic soda-silicate cement specimens to determine the statistical variation in strength of the coating material. A multiple cracking computer simulation was developed to include the statistical nature of the coating strength. The crack density, bend testing and simulation results were integrated to calculate interfacial shear strength in the Al-cement system.