Optimizing the weld strength of ultrasonically welded nylon composites

Ultrasonic welding of thermoplastic composites has become an important process in industry because of its relatively low cost and high quality resultant joints. However, the optimization of this technique has been essentially based on a trial-and-error process. In this report, an L18 orthogonal array design based on the Taguchi method was conducted to optimize the joint strength of ultrasonically welded thermoplastic composites. The materials used were 15 and 35% glass-fiber filled nylon-6 composites. Specimens for ultrasonic welding were welded on a 2000-watt welder and their joint strengths were determined by a tensile tester. The experimental result suggests that the amplitude of vibration, hold time and geometry of the energy directors are the principal factors affecting the joint property of ultrasonically welded nylon composites. Semicircular energy directors were found to weld products of the highest strength. In addition, the joint strength of the parts increases with the fiber content in the composites, but decreases with the moisture of the materials.