Thesis Abstracts 2001
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Vibration Welding of Engineering Plastics
By: 2Lt J.J. MacDonald
Abstract
This study examined the weld strength of vibration welded nylon compounds. The effect of part geometry (butt, T, and hollow parts), welding process (meltdown and weld pressure), resin (nylon 6 and 66), and glass fibre (0, 13% and 33%) parameters on weld strength was investigated using a central composite design of experiment. In addition, meltdown-time profiles were measured experimentally and compared with analytical models. The experimental results showed that weld pressure is the most important welding parameter and that lower weld pressures generally resulted in higher weld strengths. Unreinforced nylon 66 butt welds had higher weld strengths than those of unreinforced nylon 6. Both unreinforced resins, under the right welding conditions, could attain the strength of the bulk non-welded unreinforced resin. Similarly, in both nylon 6 and nylon 66, the maximum weld strength was achieved with 13% glass-fibre content, with nylon 66 achieving slightly higher results.
For the 33% glass filled materials, nylon 6 was observed to have higher weld strengths than nylon 66. This phenomenon is believed to be related to viscosity differences between the two compounds. Complex stress fields in the other geometries resulted in lower maximum stresses and were observed to be material dependent. A preliminary analysis of existing mathematical models for meltdown was performed using data generated in this study. Initial findings show good agreement between theoretical predictions and experimental results.
