Thesis Abstracts 2004
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Shear Strength of Vibration Welded Lap Welds
By: Donald D. Couzens (MASc.)
Supervisor: Dr. Philip J. Bates
Abstract
This study examined the shear strength of vibration welds between long glass fiber reinforced polypropylene (LFT) and continuously reinforced polypropylene (CFT) assemblies. The effect of welding process parameters (meltdown and weld pressure), part geometry ("Ideal" and complex), glass fibre orientation (0°, 90° and perpendicular to weld direction), and glass fiber content (GF) in the CFT (60wt% and 70wt%) on shear strength were studied. In addition, the meltdown - time and force - time profiles were measured experimentally for simple geometries. The experimental results showed weld pressure had no effect on the lap weld shear strength. However, meltdown and the CFT glass fibre content both had effects on the shear strength. It was found that the shear strength decreased as meltdown increased. The CFT with a higher glass content produced the lower shear strengths. These two changes in shear strength were attributed to an increase in the amount of GF remaining in the weld line after welding was complete.
In addition, the current Dow® adhesive used by Decoma® was tested and compared to vibration welded lap welds. The adhesive shear strengths for "Ideal" geometries were similar to those obtained with vibration welding. However, the strength obtained on more complex shapes was observed to be approximately 40% lower.
