Box Beam Lap Shear Torsion Testing for Evaluating Structural Performance of Adhesive Bonded Joints

摘要

In this study, failure strengths of in-plane shear loaded bonded joints were compared with analytical predictions of Shear Loaded Bonded Joint (SLBJ) theory. The investigation was carried out in two phases. Phase I was conducted with a particular focus placed on the effect of bondline thickness on joint strength. These specimens were fabricated using E-glass/epoxy cloth and PTM&W ES6292 two-component paste adhesive. A box beam torsion test fixture was used to apply a shear loading. Phase II was carried out to investigate adhesive and/or adherend variability in SLBJ predictions. These specimens were fabricated using aluminum and carbon adherends with Loctite and Hysol EA9360 paste adhesives. Several joggle (production-style) joints were tested to investigate the effects of joggle adherend on strength of the adhesive joint. Furthermore, a failure analysis was conducted to study the failure mechanism of these joints. Experimental data and SLBJ predictions indicated a decrease in strength as the bondline thickness was increased. SLBJ predictions for thin bondlines were comparable with experimental data, but for thick bondlines SLBJ predictions were lower than the experimental data. Substrate failure of EA9360 specimens resulted in significantly lower experimental data than SLBJ predictions. An accumulation of large plastic strains in thin bondlines resulted in high adherend interlaminar strains and caused substrate failure. The unstable damage development of thick bondlines resulted in adhesive cracking in multiple locations with a cohesive type failure and lower failure strengths than that of the thin bondlines.