In-line quality assurance of metal-plastic-hybrid parts by air-coupled ultrasound

Fast production cycles are of great importance in series production in the automotive sector. In order to enhance the amount of fiber-plastic composites into series in automotive production, it is an option to replace the thermoset matrix with a thermoplastic matrix. Organo sheets are endless fiber-reinforced sheets with a thermoplastic matrix. By heating them, they can be easily and quickly pressed into a desired shape. Back injection molding with ribs in injection molding machines is also possible. By bonding such plastic hybrid components with metals, metal-plastic hybrid components are produced which have a high stiffness due to the metal and a high energy absorption capacity due to the plastic. For example, 3D-A-pillars of motor vehicles can be produced cost-effectively in series from such hybrid components. Very important is a good connection between steel and plastic. An integrated test cell was which can be inserted into a series production process of A-pillar demonstrator components. Using air-coupled ultrasound, the entire metal-plastic bond can be tested in the cell within three minutes. By generating guided waves in the component, propagating perpendicular to the scanning direction of the transducers the latter can reach distances in the steel sheet of the A-pillar up to 40 mm. In doing so, only one scan direction is necessary which saves inspection time compared to conventional pulse echo ultrasonic testing.