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Effects of impact velocity on the crush behavior of aluminum 5052-H38 honeycomb specimens are investigated by experiments. An impact test machine using pressurized nitrogen was designed to perform dynamic crush tests. A test fixture was designed such that inclined loads can be applied to honeycomb specimens in dynamic crush tests. The results of dynamic crush tests indicate that the effects of impact velocity on the normal and inclined crush strengths are significant. The trends of the inclined crush strengths for specimens with different in-plane orientation angles as functions of impact velocity are very similar to that of the normal crush strength. Experimental results show similar progressive folding mechanisms for honeycomb specimens under pure compressive and inclined loads. Under inclined loads, the inclined stacking patterns were observed. The inclined stacking patterns are due to the asymmetric locations of the horizontal plastic hinge lines.

Failure behavior of spot welds is investigated under impact loading conditions. Three different impact speeds were selected to test both HSLA steel and mild steel specimens under combined opening and shear loading conditions. A test fixture was designed and used to obtain the failure loads of spot weld specimens of different thicknesses under a range of combined opening and shear loads with different impact speeds. Accelerometers were installed on the fixtures and the specimens for investigation of the inertia effects. Optical micrographs of the cross sections of failed spot welds were obtained to understand the failure processes in both HSLA steel and mild steel specimens under different combined impact loads. The experimental results indicate that the failure mechanisms of spot welds are very similar for both HSLA steel and mild steel specimens with the same sheet thickness. These micrographs show that the sheet thickness can affect the failure mechanisms.

Experiments to obtain the failure loads of spot welds are first reviewed under combined opening and shear loading conditions. A failure criterion is then presented for spot welds under combined opening and shear loading conditions based on the results from the experiments and a lower bound limit load analysis. In order to account for spot welds under more complex loading conditions, another lower bound limit load solution is presented to characterize the failure loads of spot welds under combinations of three forces and three moments. Based on the limit load solution, an engineering failure criterion is proposed with correction factors determined by different spot weld tests. The engineering failure criterion can be used to characterize the failure loads of spot welds with consideration of the effects of sheet thickness, nugget radius and combinations of loads.