Investigation of the Weld Line of Compression Molded GMT and UD Tape

The use of fiber-reinforced plastics (FRP) is essential to meet future lightweight construction requirements in the automotive industry. Therefore, resource- and cost-saving as well as innovative manufacturing processes are needed, which enable large-scale series production. One example is the manufacturing of such components from glass mat-reinforced thermoplastics (GMT) and unidirectional fiber tapes (UD tapes) by combined compression molding and thermoforming. It may be necessary to insert multiple GMT pieces into the mold to improve mold filling and extend the process limits. In the forming process, the different material fronts of the GMT blanks collide and are joined by fusing and consolidating the matrix material of the composite. This area is called the weld line. In this paper, the influence of the weld line on the tensile strength of the workpieces was investigated. First, two GMT blanks were placed next to each other and formed in a heated plate mold. On the basis of tensile specimens that were cut across the weld line, it was found that the weld line causes a marked decrease in tensile strength. In further investigations, the UD tapes were added into the process. Due to the reinforcement of the UD tapes, the decrease in tensile strength due to the weld line was significantly reduced.