Ultrasonic welding of thermoplastics in the far‐field

Abstract

In far‐field ultrasonic welding of plastic parts the distance between the ultrasonic horn and the joint is greater than 6 mm. This study investigated the farfield ultrasonic welding of amorphous (acrylo butadiene styrene and polystyrene) and semicrystalline (polyethylene and polypropylene) polymers. Far‐field welding worked well for amorphous polymers. Weld strength improved substantially with increasing amplitude of vibration at the joint interface. Increasing the weld pressure and/or the weld time also resulted in higher weld strengths. Far‐field ultrasonic welding was not successful for semicrystalline polymers. The parts melted and deformed at the horn/part interface with little or no melting at the joint interface. A model for wave propagation in viscoelastic materials, which was developed to predict the vibration amplitude experienced at the joint interface, indicates that increasing the length of the samples to a half a wavelength should improve the far‐field welding of semicrystalline polymers by maximizing the amplitude of vibration at the joint interface.

Fusion Bonding/Welding of Thermoplastic Composites

“…The pressure provides better energy transfer and melt-flow at the interface and improves the weld strength [32,33]. An increase in welding time increases the energy dissipation in the weld and consequently improves the weld strength up to an optimum value [32,33]. Above the optimum welding time, a large amount of flashes are formed and polymer chains are oriented in the direction of polymer flow, thus weakening joint performance.…”

“…Ultrasonic welding can also be employed for far-field welding, where the horn is more than 6 mm away from the weld interface. In this process, the strength of the joint depends on the material, the geometry of the parts, the distance between the horn and the interface, and the dynamic impedance of the fixture and the base or anvil [32].…”

“…The main processing parameters for ultrasonic welding are welding pressure, welding amplitude, welding time, and welding frequency. The pressure provides better energy transfer and melt-flow at the interface and improves the weld strength [32,33]. An increase in welding time increases the energy dissipation in the weld and consequently improves the weld strength up to an optimum value [32,33].…”

Optimizing the joint strength of ultrasonically welded thermoplastics

“…3 Although the ultrasonic welding process has been developed for more than three decades, the research effort that has been devoted to this technique is limited. Benatar and his co-workers [4][5][6] completed research in both near-field and far-field welding of different thermoplastics, including polystyrene, ABS, polyethylene, polypropylene, and PEEK graphite composites. They proposed a lumped parameter model to predict the heating rates and energy dissipation of the ultrasonic welding.…”

Thermal modeling during continuous ultrasonic welding

“…The ultrasonic welding (UW) process has been successfully used for consolidation of polymeric materials [10,11]. It was reported [7] that this is also an ideal joining process for aluminum alloys and aluminum matrix composites since the materials to be consolidated do not have to be heated to their melt temperature.…”