Vibration welding nylon 66 - Part I - Experimental study

The strengths and failure mechanisms of vibration welded joints were studied using a central composite design of experiment. The experimental study focused on three aspects: material, joint geometry and welding process effects. Butt joints, T-joints and cup-plaque joints were made using unreinforced nylon 66 and 33% short glass fiber reinforced nylon 66. Reinforced nylon 66 exhibited lower butt and T-joint strengths than unreinforced nylon 66. Analyses of the fracture surface suggest that the lower strength for the reinforced compound is related to glass fiber bundling and orientation effects. Weld pressure appears to play the largest role in determining joint strength; lower pressure results in higher strengths. Although the nominal tensile stress on these joint geometries has been shown to be a useful screening tool, a more detailed mechanical analysis is required to understand the complex stress field existing in T- and cup-plaque joints. Such an analysis should allow a better design of real joints on industrial parts.