Product Code: ICA13_601

Laser Joining of Endless Long Fiber Reinforced Thermoplastics with Aluminum
Authors:
Martin Stambke, Ilmenau University of Technology; Ilmenau Germany
Jean Pierre Bergmann, Ilmenau University of Technology; Ilmenau Germany
Benedikt Ruhdorfer, Ilmenau University of Technology; Ilmenau Germany
Presented at ICALEO 2013

Lightweight design constructions are dominated by a mix of various materials, whereas aluminum and steel alloys play an important role especially for series production with high unit numbers. Plastics and especially fiber reinforced plastics offer a very high potential for lightweight design constructions. Thus they gain more and more importance especially for mobile applications like transportation or aircraft industry. However reinforced plastics will not substitute metals in total because of economical and technical reasons.
The need to combine metals and plastics in engineering constructions create a challenge for the joining technologies because of the fundamental different characteristics of these materials. Currently cold joining technologies like screwing, riveting or adhesive bonding is mainly used to manufacture hybrid parts. In order to overcome the disadvantages of these conventional joining technologies the laser based thermal joining offers a new technology. A laser heats the metal directly and because of heat transfer through the metal sheet the temperature within the joining zone of the overlap rises. This leads to the plasticization of the thermoplastic which moistens the metal surface. After cool down, a strong joint can be obtained.
The investigations presented in this paper show the possibility to join endless long fiber reinforced thermoplastics with aluminum 6016. The metal joining partner is structured by sandblasting using F60 grain size. The samples are 50 mm in width, 75 mm in length and overlap is 20 mm. As plastic joining partner glass fiber reinforced PA66 and PP is used. In order to investigate the strength of the joint for different types of stress tensile shear strength, pealing tension and fatigue strength tests are performed. The first results of ongoing experiments show separation forces up to more than 7 kN using PA66 as matrix material. Trials carried out with the matrix material PP showed significantly lower separation forces of 2 kN in a maximum. The process investigation showed a strong correlation between the process parameters laser power and feeding and the achievable separation force. This leads to the conclusion that the joining temperature has to be adjusted carefully to the melting temperature of matrix material since it can be considered that it is mostly responsible for the formation of the joint. Metallographic investigations show that the glass fiber reinforcement acts as crack suppression up to a certain point.