Ultrasonic joining: A novel direct-assembly technique for metal-composite hybrid structures

Abstract

Ultrasonic joining (U-Joining) is a new direct assembly technique developed by Helmholtz-Zentrum Geesthacht that uses ultrasonic energy to join fiber-reinforced thermoplastics to surface-structured metallic parts produced by metal injection molding. Ultrasonic vibration and pressure create frictional heat at the materials interface, which softens the composite matrix and allows the reinforcement (structured on the surface of the metallic part) to penetrate the composite. As a result, a metal-composite hybrid joint with improved out-of-plane strength is achieved. In this work, the features of U-Joining are briefly introduced, and the feasibility of the technique is demonstrated with Ti-6Al-4V/glass-fiber-reinforced polyetherimide joints. Optical microscopy reveals that a close contact between metal and composite was achieved after U-joining. Lap shear testing of six-pin joints showed an improvement in strength of up to 5.5 times (2011±530 N) that of pin-less reference joints (368±29 N).