Demonstrator:
The aim of the FlexHyJoin project was to set up a fully automated production cell for joining metal with TP-FRPC for the automotive application. The validation of the developed technologies was performed with a roof stiffener for a Fiat Panda. Laser-structured metal brackets are attached to a TP-FRPC roof stiffener located behind the B-pillar to facilitate the assembly to the car body.
Joining processes:
Laser joining (LJ) and induction joining (IJ) were selected as suitable joining methods. LJ is more purposeful for smaller and more complex geometries, while IJ has advantages for larger geometries. The most relevant joining parameters affecting bonding strength were investigated in order to obtain the ideal parameters for the joining process and process time. In addition, clamping and pressing devices for both joining methods were developed which were specially designed for the demonstrator’s geometry. The temperature distribution in the materials to be connected and in the joining zone itself was optimized, and the joining path was introduced as a quality assurance feature. FlexHyJoin represents a solution for mass series application for IJ as well as the combination of LJ and IJ.
Surface pre-treatment:
To improve the bonding strength, the surface of the metallic joining partners is textured using a single mode cw (continuous wave) fibre laser. This increases the joining surface and the mechanical clamping by undercuts.
Process Simulation:
Finite element (FE) simulations were performed and their results validated in order to analyse the joining processes and the bond strength, as well as the behaviour of the joint. Explicit thermal simulations were created to simulate the IJ and LJ processes.
Quality assurance:
Lock-in Thermography was selected as the quality assurance method. With the help of this non-destructive testing (NDT) method, the requirements for a complete and fully automated quality assurance of the joint were realized.
Prototype production cell:
All individually developed process components were integrated into a fully automated production cell for the joining of a thermoplastic roof stiffener with 3 metal brackets (left, right, central). An articulated 6-axis robot transports the respective material component to each process step and places them in the clamping devices. Various monitoring systems were implemented in the production cell. The individual processes are monitored either with thermal monitoring systems, such as pyrometers and thermal cameras, or highly precise measuring systems, e.g. displacement sensors.
Dissemination / Exploitation:
The project results were made available to a broad expert audience through numerous publications, presentations at issue-specific conferences and exhibition appearances. One highlight was the participation at the EU Industry Day in Brussels in February 2018, presenting the roof stiffener demonstrator part among various current Horizon 2020 research projects. In March, a re-engineered Fiat Panda body-in-white was exhibited during the world’s largest fair on composites (JEC) in Paris. During a first dissemination event at a medium-size conference on material innovations (MatX) in June in Nuremberg, both of the above mentioned exhibition pieces were shown. This was enhanced by oral presentations, a workshop on the future of hybrid materials and making the production cell come alive by a virtual reality system for all conference participants to try out. Furthermore, the FlexHyJoin technology was presented to industrial companies from the automotive industry at a dissemination event in Italy in October. The functionality of the prototype production cell was successfully demonstrated live during a project closing dissemination event open to the public in December 2018 at one of the consortium members’ company site.
