A Tapered Bondline Thickness Double Cantilever Beam (DCB) Specimen Geometry for Combinatorial Fracture Studies of Adhesive Bonds

摘要

This study proposes and demonstrates the use of a DCB specimen with a linearly varying bondline thickness as a potential "combinatorial specimen" for characterization of the effect of bondline thickness on fracture energy. Data from linearly increasing or linearly decreasing bondline thickness specimens generally showed good agreement with data from constant bondline thickness specimens. It was observed that a single DCB specimen with a linearly increasing or decreasing bondline thickness could provide significant insight into the effect of bondline thickness on fracture energy. This might result in a reduction in testing efforts needed to study the effect of bondline thickness on the fracture energy of a toughened epoxy adhesive system. Concerns would be raised, however, if the bonds exhibited a clear R-curve behavior, which could obscure the results of this combinatorial specimen configuration. A preliminary study using finite element analysis on the mentioned geometries indicates similar plastic zone sizes in constant and tapered bondline thickness specimens, although more studies would be needed to confirm this observation. The successful extension of these tapered bondline thickness specimens to other adhesive and adherend combinations is expected, although additional testing should be conducted to determine possible issues and limitations.