INCREASING THE STRENGTH OF MECHANICALLY JOINED CONNECTIONS OF METAL AND FIBER-REINFORCED PLASTICS USING A STRUCTURED AUXILIARY JOINING ELEMENT

摘要

The low plasticity in comparison to metals represents a limiting factor for fiber-reinforced plastics in mechanical joining systems. While previous approaches to solving this problem have provided for new joining processes or local metal sheet inserts in the fiber composite, the present study aims at a pin-structured auxiliary joining element as a new technology support for increasing the load-bearing capacity of mechanical joints between metal and fiber reinforced plastics. The increase in load-bearing capacity principle is based on the relieving of critical hole edge areas of the FRP by introducing loads across the pin structures of the auxiliary joining element. Therefore, the following paper shows different approaches in manufacturing of the new type of auxiliary joining element with integrated pin structures. Furthermore, the influences of the pin-geometry on the composite fracture behavior by insertion under various heating strategies have been investigated, whereas ultrasonic assisted insertion leads to favourable results. To define the most effective manufacturing process for a pin-structured auxiliary joining element with increasing in load-bearing capacity ability single-lap tests for detecting the shear tensile strength were examined. With an improvement of the load-bearing capacity of up to 47%, auxiliary joining elements with ten pins, produced by a combined punch-forming process, have achieved the highest shear tensile strengths.